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  Subjects -> ENGINEERING (Total: 2270 journals)
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ENGINEERING (1199 journals)                  1 2 3 4 5 6 | Last

Showing 1 - 200 of 1205 Journals sorted alphabetically
3 Biotech     Open Access   (Followers: 7)
3D Research     Hybrid Journal   (Followers: 19)
AAPG Bulletin     Full-text available via subscription   (Followers: 5)
AASRI Procedia     Open Access   (Followers: 15)
Abstract and Applied Analysis     Open Access   (Followers: 3)
Aceh International Journal of Science and Technology     Open Access   (Followers: 2)
ACS Nano     Full-text available via subscription   (Followers: 217)
Acta Geotechnica     Hybrid Journal   (Followers: 6)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Polytechnica : Journal of Advanced Engineering     Open Access   (Followers: 2)
Acta Scientiarum. Technology     Open Access   (Followers: 3)
Acta Universitatis Cibiniensis. Technical Series     Open Access  
Active and Passive Electronic Components     Open Access   (Followers: 7)
Adaptive Behavior     Hybrid Journal   (Followers: 10)
Adıyaman Üniversitesi Mühendislik Bilimleri Dergisi     Open Access  
Adsorption     Hybrid Journal   (Followers: 4)
Advanced Engineering Forum     Full-text available via subscription   (Followers: 4)
Advanced Science     Open Access   (Followers: 4)
Advanced Science Focus     Free   (Followers: 3)
Advanced Science Letters     Full-text available via subscription   (Followers: 5)
Advanced Science, Engineering and Medicine     Partially Free   (Followers: 7)
Advanced Synthesis & Catalysis     Hybrid Journal   (Followers: 17)
Advances in Artificial Neural Systems     Open Access   (Followers: 4)
Advances in Calculus of Variations     Hybrid Journal   (Followers: 2)
Advances in Catalysis     Full-text available via subscription   (Followers: 5)
Advances in Complex Systems     Hybrid Journal   (Followers: 7)
Advances in Engineering Software     Hybrid Journal   (Followers: 25)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 14)
Advances in Fuzzy Systems     Open Access   (Followers: 5)
Advances in Geosciences (ADGEO)     Open Access   (Followers: 9)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 19)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 23)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 8)
Advances in Natural Sciences: Nanoscience and Nanotechnology     Open Access   (Followers: 28)
Advances in Operations Research     Open Access   (Followers: 11)
Advances in OptoElectronics     Open Access   (Followers: 5)
Advances in Physics Theories and Applications     Open Access   (Followers: 12)
Advances in Polymer Science     Hybrid Journal   (Followers: 40)
Advances in Porous Media     Full-text available via subscription   (Followers: 4)
Advances in Remote Sensing     Open Access   (Followers: 35)
Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Aerobiologia     Hybrid Journal   (Followers: 1)
African Journal of Science, Technology, Innovation and Development     Hybrid Journal   (Followers: 4)
AIChE Journal     Hybrid Journal   (Followers: 28)
Ain Shams Engineering Journal     Open Access   (Followers: 5)
Akademik Platform Mühendislik ve Fen Bilimleri Dergisi     Open Access  
Alexandria Engineering Journal     Open Access   (Followers: 1)
AMB Express     Open Access   (Followers: 1)
American Journal of Applied Sciences     Open Access   (Followers: 27)
American Journal of Engineering and Applied Sciences     Open Access   (Followers: 11)
American Journal of Engineering Education     Open Access   (Followers: 9)
American Journal of Environmental Engineering     Open Access   (Followers: 16)
American Journal of Industrial and Business Management     Open Access   (Followers: 23)
Analele Universitatii Ovidius Constanta - Seria Chimie     Open Access  
Annals of Combinatorics     Hybrid Journal   (Followers: 3)
Annals of Pure and Applied Logic     Open Access   (Followers: 2)
Annals of Regional Science     Hybrid Journal   (Followers: 7)
Annals of Science     Hybrid Journal   (Followers: 7)
Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 2)
Applicable Analysis: An International Journal     Hybrid Journal   (Followers: 1)
Applied Catalysis A: General     Hybrid Journal   (Followers: 6)
Applied Catalysis B: Environmental     Hybrid Journal   (Followers: 8)
Applied Clay Science     Hybrid Journal   (Followers: 4)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 12)
Applied Magnetic Resonance     Hybrid Journal   (Followers: 3)
Applied Nanoscience     Open Access   (Followers: 7)
Applied Network Science     Open Access  
Applied Numerical Mathematics     Hybrid Journal   (Followers: 5)
Applied Physics Research     Open Access   (Followers: 3)
Applied Sciences     Open Access   (Followers: 2)
Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 4)
Arabian Journal for Science and Engineering     Hybrid Journal   (Followers: 5)
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 4)
Archives of Foundry Engineering     Open Access  
Archives of Thermodynamics     Open Access   (Followers: 7)
Arkiv för Matematik     Hybrid Journal   (Followers: 1)
ASEE Prism     Full-text available via subscription   (Followers: 2)
Asian Engineering Review     Open Access  
Asian Journal of Applied Science and Engineering     Open Access   (Followers: 1)
Asian Journal of Applied Sciences     Open Access   (Followers: 2)
Asian Journal of Biotechnology     Open Access   (Followers: 7)
Asian Journal of Control     Hybrid Journal  
Asian Journal of Current Engineering & Maths     Open Access  
Asian Journal of Technology Innovation     Hybrid Journal   (Followers: 8)
Assembly Automation     Hybrid Journal   (Followers: 2)
at - Automatisierungstechnik     Hybrid Journal   (Followers: 1)
ATZagenda     Hybrid Journal  
ATZextra worldwide     Hybrid Journal  
Australasian Physical & Engineering Sciences in Medicine     Hybrid Journal   (Followers: 1)
Australian Journal of Multi-Disciplinary Engineering     Full-text available via subscription   (Followers: 2)
Autonomous Mental Development, IEEE Transactions on     Hybrid Journal   (Followers: 7)
Avances en Ciencias e Ingeniería     Open Access  
Balkan Region Conference on Engineering and Business Education     Open Access   (Followers: 1)
Bangladesh Journal of Scientific and Industrial Research     Open Access  
Basin Research     Hybrid Journal   (Followers: 3)
Batteries     Open Access   (Followers: 3)
Bautechnik     Hybrid Journal   (Followers: 1)
Bell Labs Technical Journal     Hybrid Journal   (Followers: 23)
Beni-Suef University Journal of Basic and Applied Sciences     Open Access   (Followers: 3)
BER : Manufacturing Survey : Full Survey     Full-text available via subscription   (Followers: 2)
BER : Motor Trade Survey     Full-text available via subscription   (Followers: 1)
BER : Retail Sector Survey     Full-text available via subscription   (Followers: 2)
BER : Retail Survey : Full Survey     Full-text available via subscription   (Followers: 2)
BER : Survey of Business Conditions in Manufacturing : An Executive Summary     Full-text available via subscription   (Followers: 3)
BER : Survey of Business Conditions in Retail : An Executive Summary     Full-text available via subscription   (Followers: 3)
Bharatiya Vaigyanik evam Audyogik Anusandhan Patrika (BVAAP)     Open Access   (Followers: 1)
Biofuels Engineering     Open Access  
Biointerphases     Open Access   (Followers: 1)
Biomaterials Science     Full-text available via subscription   (Followers: 9)
Biomedical Engineering     Hybrid Journal   (Followers: 16)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 13)
Biomedical Engineering Letters     Hybrid Journal   (Followers: 5)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 16)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 31)
Biomedical Engineering: Applications, Basis and Communications     Hybrid Journal   (Followers: 5)
Biomedical Microdevices     Hybrid Journal   (Followers: 8)
Biomedical Science and Engineering     Open Access   (Followers: 3)
Biomedizinische Technik - Biomedical Engineering     Hybrid Journal  
Biomicrofluidics     Open Access   (Followers: 4)
BioNanoMaterials     Hybrid Journal   (Followers: 1)
Biotechnology Progress     Hybrid Journal   (Followers: 39)
Boletin Cientifico Tecnico INIMET     Open Access  
Botswana Journal of Technology     Full-text available via subscription  
Boundary Value Problems     Open Access   (Followers: 1)
Brazilian Journal of Science and Technology     Open Access   (Followers: 2)
Broadcasting, IEEE Transactions on     Hybrid Journal   (Followers: 10)
Bulletin of Canadian Petroleum Geology     Full-text available via subscription   (Followers: 14)
Bulletin of Engineering Geology and the Environment     Hybrid Journal   (Followers: 3)
Bulletin of the Crimean Astrophysical Observatory     Hybrid Journal  
Cahiers, Droit, Sciences et Technologies     Open Access  
Calphad     Hybrid Journal  
Canadian Geotechnical Journal     Full-text available via subscription   (Followers: 13)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 40)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 7)
Case Studies in Thermal Engineering     Open Access   (Followers: 3)
Catalysis Communications     Hybrid Journal   (Followers: 6)
Catalysis Letters     Hybrid Journal   (Followers: 2)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysis Today     Hybrid Journal   (Followers: 5)
CEAS Space Journal     Hybrid Journal  
Cellular and Molecular Neurobiology     Hybrid Journal   (Followers: 3)
Central European Journal of Engineering     Hybrid Journal   (Followers: 1)
CFD Letters     Open Access   (Followers: 6)
Chaos : An Interdisciplinary Journal of Nonlinear Science     Hybrid Journal   (Followers: 2)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 3)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 2)
Chinese Journal of Engineering     Open Access   (Followers: 2)
Chinese Science Bulletin     Open Access   (Followers: 1)
Ciencia e Ingenieria Neogranadina     Open Access  
Ciencia en su PC     Open Access   (Followers: 1)
Ciencias Holguin     Open Access   (Followers: 1)
CienciaUAT     Open Access  
Cientifica     Open Access  
CIRP Annals - Manufacturing Technology     Full-text available via subscription   (Followers: 11)
CIRP Journal of Manufacturing Science and Technology     Full-text available via subscription   (Followers: 14)
City, Culture and Society     Hybrid Journal   (Followers: 21)
Clay Minerals     Full-text available via subscription   (Followers: 9)
Clean Air Journal     Full-text available via subscription   (Followers: 2)
Coal Science and Technology     Full-text available via subscription   (Followers: 3)
Coastal Engineering     Hybrid Journal   (Followers: 11)
Coastal Engineering Journal     Hybrid Journal   (Followers: 4)
Coatings     Open Access   (Followers: 2)
Cogent Engineering     Open Access   (Followers: 2)
Cognitive Computation     Hybrid Journal   (Followers: 4)
Color Research & Application     Hybrid Journal   (Followers: 1)
COMBINATORICA     Hybrid Journal  
Combustion Theory and Modelling     Hybrid Journal   (Followers: 13)
Combustion, Explosion, and Shock Waves     Hybrid Journal   (Followers: 13)
Communications Engineer     Hybrid Journal   (Followers: 1)
Communications in Numerical Methods in Engineering     Hybrid Journal   (Followers: 2)
Components, Packaging and Manufacturing Technology, IEEE Transactions on     Hybrid Journal   (Followers: 23)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Composite Structures     Hybrid Journal   (Followers: 252)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 177)
Composites Part B : Engineering     Hybrid Journal   (Followers: 223)
Composites Science and Technology     Hybrid Journal   (Followers: 164)
Comptes Rendus Mécanique     Full-text available via subscription   (Followers: 2)
Computation     Open Access  
Computational Geosciences     Hybrid Journal   (Followers: 12)
Computational Optimization and Applications     Hybrid Journal   (Followers: 7)
Computational Science and Discovery     Full-text available via subscription   (Followers: 2)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 6)
Computer Science and Engineering     Open Access   (Followers: 17)
Computers & Geosciences     Hybrid Journal   (Followers: 25)
Computers & Mathematics with Applications     Full-text available via subscription   (Followers: 5)
Computers and Electronics in Agriculture     Hybrid Journal   (Followers: 4)
Computers and Geotechnics     Hybrid Journal   (Followers: 8)
Computing and Visualization in Science     Hybrid Journal   (Followers: 6)
Computing in Science & Engineering     Full-text available via subscription   (Followers: 25)
Conciencia Tecnologica     Open Access  
Concurrent Engineering     Hybrid Journal   (Followers: 3)
Continuum Mechanics and Thermodynamics     Hybrid Journal   (Followers: 6)
Control and Dynamic Systems     Full-text available via subscription   (Followers: 8)
Control Engineering Practice     Hybrid Journal   (Followers: 41)
Control Theory and Informatics     Open Access   (Followers: 7)
Corrosion Science     Hybrid Journal   (Followers: 24)
CT&F Ciencia, Tecnologia y Futuro     Open Access  
CTheory     Open Access  

        1 2 3 4 5 6 | Last

Journal Cover Current Applied Physics
  [SJR: 0.716]   [H-I: 55]   [4 followers]  Follow
    
   Full-text available via subscription Subscription journal
   ISSN (Print) 1567-1739
   Published by Elsevier Homepage  [3031 journals]
  • First-principal calculations of electronic and optical properties of
           Fe1−xZnxS2 and Zn1−xMgxO alloys
    • Abstract: Publication date: Available online 19 May 2017
      Source:Current Applied Physics
      Author(s): N. Ouarab, M. Boumaour
      Electronic properties of Fe1−xZnxS2 and Zn1−xMgxO alloys are performed by using full potential linearized augmented plane wave method (FP-LAPW). Band gap energies have been calculated by using concomitantly the LDA with Tran Blaha modified Becke-Johnson (TB-mBJ) potentials. The corrected positions related to valence band maximum (VBM) and conduction band minimum (CBM) have been evaluated by many-body perturbation theory in the GW approximation. The electron affinities of these alloys are determined by knowledge the exact position of CBM from the fit of total density of states (TDOS). In the case of 0 at % of (Zn, Mg) alloyed element, pyrite FeS2 and wurtzite ZnO, respectively, exhibit positive electron affinities of 3.34 eV and 4.34 eV, which are in close with experimental measurements. As for optical properties, the absorption coefficient spectra and refraction index variations are performed from momentum matrix elements and interpreted via the projected density of states. The studied alloys show significant responses in visible range and a blue shift in connection with increasing the alloyed element.

      PubDate: 2017-05-20T21:06:30Z
       
  • Optical polarization in mono and bilayer MoS2
    • Abstract: Publication date: Available online 19 May 2017
      Source:Current Applied Physics
      Author(s): Youngsin Park, Nannan Li, Christopher C.S. Chan, Benjamin P.L. Reid, Robert A. Taylor, Hyunsik Im
      Optical anisotropy in monolayer- and bilayer-MoS2 was investigated by polarization resolved photoluminescence measurements. The photoluminescence of monolayer-MoS2 is found to be partially polarized at 4.2 K and maintains this polarization characteristic up to room temperature, while the photoluminescence of bilayer-MoS2 shows no obvious polarization. This polarization anisotropy is due to strain effects at the interface between the MoS2 layer and the SiO2 substrate, causing symmetry breaking of the MoS2 charge distribution. Calculations using density functional theory of the electron density distribution of the monolayer- and bilayer-MoS2 in the in-plane direction are also presented, giving support to our qualitative analysis.

      PubDate: 2017-05-20T21:06:30Z
       
  • Mixing sequence driven controlled dispersion of graphene oxide in PC/PMMA
           blend nanocomposite and its effect on thermo-mechanical properties
    • Abstract: Publication date: Available online 17 May 2017
      Source:Current Applied Physics
      Author(s): Santosh Kr. Tiwari, Goutam Hatui, Ramesh Oraon, Amrita De Adhikari, Ganesh Chandra Nayak
      Herein, we report an efficient approach for the fabrication of polymer blend nanocomposites with well-dispersed graphene oxide in polycarbonate (PC)/poly methyl methacrylate (PMMA) through melt compounding under the controlled temperature and pressure. Graphene oxide was synthesized by Improved Hummer's method and consequently dispersed in PC and PMMA through different mixing sequences to access their dispersion in the blend nanocomposites. Thermo-mechanical investigations indicate ∼119.4% increase in tensile strength, ∼64.87% increase in the Young's modulus and ∼16.3% increase in glass transition value for the sample prepared by mixing GO first with PMMA and then with PC, in comparison to neat blend. This reinforcement in thermo-mechanical properties of sample prepared by mixing GO first with PMMA and then with PC, on incorporation of 1% of graphene oxide (by weight) is due to the effective interfacial adhesion and uniform load transfer at the interfaces of polymer blend nanocomposites. Furthermore, Thermogravimetric analysis showed a remarkable decrease in weight loss at elevated temperature for the nanocomposites, which confirms the role of graphene oxide on thermal stability of PNCs. The fabricated blend nanocomposites are ecofriendly, cost effective and can be used for various industrial applications where elevated temperature is required.
      Graphical abstract image

      PubDate: 2017-05-20T21:06:30Z
       
  • Comparison of desorption enhancement methods in the low temperature plasma
           ionization mass spectrometry for detecting fatty acids in Drosophila
    • Abstract: Publication date: August 2017
      Source:Current Applied Physics, Volume 17, Issue 8
      Author(s): Shin Hye Kim, Hyun Jun Jang, Jeong Hyang Park, Hyoung Jun Lee, Jeongkwon Kim, Yong-Hyeon Yim, Dan Bee Kim, Sohee Yoon
      Mass spectrometry (MS) with low temperature plasma (LTP) as an ionization source is one of the widely used ambient methods in analyzing various bio-chemical samples for their detection, identification, differentiation, etc. While the LTP-MS allows selective analysis of a sample with low-molecular weight without thermal damages, it has difficulties desorbing a target molecule from the sample surface with a low volatility. Hence, for the purpose of enhancing the desorption and ionization efficiencies of the LTP-MS when analyzing the fatty acids, two methods were compared: directly heating the sample surface and increasing the vapor pressure of the fatty acid itself by derivatization. In addition, the fatty acids in Drosophila were directly analyzed with the LTP-MS. As a result, it was found that the LTP-MS detection efficiency was enhanced with the derivatization as much as with the heating condition while there was little synergy in employing both of the heating and derivatization together.

      PubDate: 2017-05-15T20:46:35Z
       
  • The structural analysis of MWCNT-SiO2 and electrical properties on device
           application
    • Abstract: Publication date: Available online 12 May 2017
      Source:Current Applied Physics
      Author(s): Adem Kocyigit, Ikram Orak, İbrahim Karteri, Serhan Uruş
      Al/MWCNT-SiO2/p-Si device were obtained using chemical techniques and characterized using the I-V (under dark and light conditions) and C-V measurements depending on various frequency. MWCNT-SiO2 composite layer of the device were also characterized using XRD, FTIR, SEM, TEM and TGA measurements. These all results indicated that the MWCNT-SiO2 layer synthesized successfully on Si wafer as a composite form with chemical processes and spin coating. I-V measurements showed that device has good rectifying properties, small saturation current and good photodiode properties. Solar cell conversion efficiency ( η p ) and fill factor (FF) values of the device also were calculated as 0.12% and 47.6%, respectively. It could be seen from C-V measurements that capacitance and conductance properties of the device strongly depended on frequency and voltage. It may be used and improved this device as rectifier, photodiode and capacitor in the future.

      PubDate: 2017-05-15T20:46:35Z
       
  • In-situ analysis energy level alignment at solution processed HAT(CN)6/PVK
           (PVK:TAPC) interface via XPS and UPS
    • Abstract: Publication date: August 2017
      Source:Current Applied Physics, Volume 17, Issue 8
      Author(s): N.A. Talik, B.K. Yap, C.Y. Tan, T.J. Whitcher
      We present in-depth analysis of an n/p heterojunction that consists of 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT(CN)6) (n-type) and Poly(9-vinylcarbazole) (PVK) (p-type) via X-ray Photoelectron Spectroscopy (XPS) and Ultra-violet Photoelectron Spectroscopy (UPS) measurement. The p-type layer is doped with 2 wt% of 1,1-bis-(4-bis(4-tolyl)-aminophenyl) cyclohexene (TAPC). The energy difference (ΔE) at the hetero-junction, magnitude of band bending (V b ) and the vacuum level shift at the interface is modified when PVK is doped with 2 wt% TAPC. The presence of V b at the HAT(CN)6/PVK (PVK:TAPC) interface makes it easier to reach a ΔE ≈ 0 energy offset in order to facilitate charge generation at the interface. Via a Fowler-Nordheim (FN) tunneling curve, it is found that the electron extraction from PVK to HAT(CN)6 at the interface could occur via the tunneling process. This finding provides new insights into novel solutions for high efficiency tandem OLEDs.
      Graphical abstract image

      PubDate: 2017-05-10T20:20:19Z
       
  • Optical investigation of oxygen defect states in SrTiO3 epitaxial thin
           films
    • Abstract: Publication date: Available online 10 May 2017
      Source:Current Applied Physics
      Author(s): Il Wan Seo, Y.S. Lee, Sang A. Lee, Woo Seok Choi
      We investigated oxygen defect states in SrTiO3 (STO) thin films by using photoluminescence spectroscopy and spectroscopic ellipsometry. The oxygen-deficient STO homoepitaxial films were fabricated by using different oxygen pressures and different oxygen flow rates for controlling the amount of oxygen vacancies systematically. The visible emission and absorption increased simultaneously with the increasing concentration of oxygen vacancies in the STO thin films. Given the absolute values of the optical constants, we discussed the origins of the visible absorption features in the STO thin films, in relation to the defect formation and related electronic reconstruction.

      PubDate: 2017-05-10T20:20:19Z
       
  • Phase separation suppression in InxGa1−xN on a Si substrate using an
           indium modulation technique
    • Abstract: Publication date: Available online 10 May 2017
      Source:Current Applied Physics
      Author(s): Hyeonseok Woo, Hansol Jo, Jongmin Kim, Sangeun Cho, Yongcheol Jo, Cheong Hyun Roh, Jun Ho Lee, Yonggon Seo, Jungho Park, Hyungsang Kim, Cheol-Koo Hahn, Hyunsik Im
      A high quality, single phase InGaN film is fabricated on a GaN/Si (111) substrate by optimizing the pulse patterned In supply with a plasma-assisted MBE technique. Compositional phase separation in InGaN is considerably suppressed. The optical and structural properties of the single phase InGaN epitaxial film are consistently confirmed by atomic force microscopy, X-ray diffraction and photoluminescence measurements. We propose a growth mechanism for single phase InGaN in terms of optimal incorporation and surface migration of In atoms.

      PubDate: 2017-05-10T20:20:19Z
       
  • Hybrid color-conversion layers for white emission from fluorescent blue
           organic light-emitting diodes
    • Abstract: Publication date: Available online 9 May 2017
      Source:Current Applied Physics
      Author(s): Seung-Hwan Lee, Deuk Su Jo, Bong Sung Kim, Dae-Ho Yoon, Heeyeop Chae, Ho-Kyoon Chung, Sung Min Cho
      Hybrid color-conversion layers (CCLs) were developed to convert a blue emission from fluorescent organic light-emitting diodes (OLEDs) to obtain a white emission with a high color rendering index (CRI). The hybrid CCLs were composed of an inorganic phosphor, organic dye, and silicon dioxide (SiO2) scattering nanoparticles. The inorganic phosphors convert a part of blue emission from OLEDs to a green-yellow emission effectively. A part of the green-yellow emission was consecutively converted to a red emission with the organic dye. Using the hybrid CCLs, we obtained a balanced white emission with the highest CRI of 93 and the color temperature of 3500 K. The high CRI white OLED showed the power efficiency of 11 lm/W which was enhanced by 1.9 times from that of the blue fluorescent OLED. We showed that the utilization of the SiO2 nanoparticles did not only enhance the power efficiency but also significantly reduce the white color variation to the viewing angle.
      Graphical abstract image

      PubDate: 2017-05-10T20:20:19Z
       
  • Ground state opto-electronic and thermoelectric response of cubic XSnO3
           (X = Ba, Sr) compounds
    • Abstract: Publication date: August 2017
      Source:Current Applied Physics, Volume 17, Issue 8
      Author(s): M. Bilal Saddique, Muhammad Rashid, Adnan Afzal, Shahid M. Ramay, Farooq Aziz, Asif Mahmood
      The density functional has been implemented to deliberate the cubic perovskite XSnO3 (X = Ba, Sr) for their elastic, electronic, optical as well as thermoelectric characteristic. The XSnO3 (X = Ba, Sr) illustrates good pact of lattice parameter for these iso-structural compounds having cubic perovskite structure. The generalized gradient approximation based on the exchange-correlation functional is applied for computing structural and mechanical characteristic, whereas the electronic, optical and thermoelectric properties have been studied by the functional suggested by Tran and Blaha that is termed as of modified Becke-Johnson (mBJ) functional. The thermodynamics stability is recognized through the expression of enthalpies of formation, which is further verified from the calculated structural properties of cubic perovskite XSnO3 (X = Ba, Sr). Moreover, various elastic parameters such has bulk modules B, Cij, shear modulus G, Young's modulus Y, anisotropy factor, B/G ratio and Poisson's ratio ν have also been reported. It has been observed by band structure computation that the studied compounds exhibit an indirect band gap between the unoccupied Ba/Sr 6s/5s and the occupied O 2p orbitals. Detailed study of optical properties is presented under the incident photon energy upto 28 eV. Our computed static dielectric constant ε 2(0) and refractive index n(0) are comparable with other theoretical and experimental values. Thermoelectric properties are presented in terms of computed Seebeck coefficient, electrical and thermal conductivities and their variation with the rise in temperature suggest that the studied compounds may find applications in the construction of various thermo-electric devices.

      PubDate: 2017-05-05T19:55:19Z
       
  • Enhanced cycle stability of silicon nanoparticles coated with
           nitrogen-doped carbon layer for lithium-ion battery anode
    • Abstract: Publication date: August 2017
      Source:Current Applied Physics, Volume 17, Issue 8
      Author(s): Hun Seok Choi, Su Jae Kim, Hyun Woo Choi, Cheul-Eon Park, Ying Jun Gao, Yang Hang, Se-Young Jeong, Jong-Pil Kim, Jong-Seong Bae, Chae-Ryong Cho
      We prepared single-crystal Si nanoparticles (Si NPs) ∼50 nm in diameter using a laser photopyrolysis technique and formed a nitrogen-doped carbon layer on them using pyrrole and FeCl3 to increase the cycle stability of the Si anodes during volume expansion and contraction. The surface chemical bonding states of the nitrogen-doped carbon-coated Si NPs were investigated. The specific capacity and capacity retention of the sample with 1 g of FeCl3 were the highest at approximately 967.1 mAh g−1 and 87.3% after 300 cycles at 1 C, respectively. The diffusion coefficient of Li ions after 1000 test cycles was 9.64 × 10−8 cm2 s-1. The higher cycling stability of the Si@NC NPs could be attributed to the nitrogen-doped carbon layers, which provided an efficient transport pathway for the electrons.

      PubDate: 2017-05-05T19:55:19Z
       
  • Significant photoinduced increment of reflectivity coefficient in
           LiNa5Mo9O30
    • Abstract: Publication date: Available online 3 May 2017
      Source:Current Applied Physics
      Author(s): M. Chrunik, A. Majchrowski, K. Ozga, M. Ya. Rudysh, I.V. Kityk, A.O. Fedorchuk, V. Yo. Stadnyk, M. Piasecki
      Synthesis of LiNa5Mo9O30 micropowders by means of sol-gel method through the citrate way was carried out. The DFT band structure calculations for obtained powders were done. Following the performed calculations, investigations of various optical functions as well as elastic properties were carried out. Basing on the analysis of the obtained results we performed photoinducing treatment of the samples near and outside the first UV spectral maximum of reflectivity (R) using the radiation of photoinducing UV nanosecond laser at 337 nm and second harmonic generated 532 nm signal originating from Nd:YAG laser emitting 1064 nm radiation, respectively. Significant enhancement of relative reflectivity (ΔR/R) in the spectral range 335–413 nm (3.7–3.0 eV) caused by photoinducing UV nanosecond laser treatment at 337 nm was observed. Huge sensitivity to the wavelength of photoinducing radiation of LiNa5Mo9O30 reflectivity was found. Discovered phenomenon indicates the possibility of LiNa5Mo9O30 application as an efficient optical trigger. Additionally it may be of huge importance for the production of high selective sensors of the laser light. Moreover, in a future we can use LiNa5Mo9O30 crystalline powder to make composite by embedding into polymer or glass matrices.
      Graphical abstract image

      PubDate: 2017-05-05T19:55:19Z
       
  • Glassy carbon electrode modified with poly(methyl orange) as an
           electrochemical platform for the determination of 4-nitrophenol at
           nanomolar levels
    • Abstract: Publication date: Available online 2 May 2017
      Source:Current Applied Physics
      Author(s): Krishnan Giribabu, Yuvaraj Haldorai, Muruganantham Rethinasabapathy, Sung-Chan Jang, Ranganathan Suresh, Wan-Seob Cho, Young-Kyu Han, Changhyun Roh, Yun Suk Huh, Vengidusamy Narayanan
      In this study, poly(methyl orange) (PMO) was synthesized by electrodeposition onto a glassy carbon electrode (GCE), and the resulting structure was examined for the determination of 4-nitrophenol (4-NP). Cyclic voltammetry revealed that the PMO-modified GCE (PMO/GCE) exhibited excellent electrocatalytic activity for the oxidation of 4-NP in a 0.5-M phosphate buffer solution. In contrast, the bare GCE showed no oxidation peak. Interestingly, PMO/GCE exhibited an oxidation peak at approximate 0.93 V, and the background current was higher than that of the bare GCE. Furthermore, the developed electrochemical sensor exhibited a linear relationship with the 4-NP concentration from 600 nM to 10 μM, and the limit of detection was 170 nM (signal/noise = 3). The sensor demonstrated excellent selectivity, good stability, and reproducibility. It was applied to the determination of 4-NP in water samples by the standard addition method and gave recoveries of 99.2–100.9%.

      PubDate: 2017-05-05T19:55:19Z
       
  • Morphological design of optical cavities for frequency-selective black
           absorbers
    • Abstract: Publication date: August 2017
      Source:Current Applied Physics, Volume 17, Issue 8
      Author(s): Da-Som Kim, Jin-Woo Cho, KeumHwan Park, Young-Seok Kim, Sun-Kyung Kim
      We study various morphological effects due to optical cavities that are formed into metal substrates for the implementation of frequency-selective black absorbers. The absorption spectra (λ = 500–3000 nm) of patterned metal substrates are investigated by conducting full-vectorial electromagnetic simulations. The diameter of optical cavities determines a cut-off wavelength at which absorption begins to drop off exponentially. The cut-off wavelength is gradually redshifted by increasing the diameter of the optical cavities, which is associated with the tuning of the fundamental transverse mode. The height of optical cavities determines the number and amplitude of absorption peaks, which originate from Fabry-Perot modes with different longitudinal orders. Also, the absorption features depend strongly on the refractive index of the material within optical cavities; optical cavities filled with a dielectric yield improved absorption, even with a relatively shallow height. With an integration of patterned tantalum (Ta) and tungsten (W) thermal emitters, the power conversion efficiencies of thermophotovoltaics are predicted, accounting a body temperature of 1300 K and the quantum efficiency of a typical infrared photovoltaic cell. Tailored optical cavities lead to a dramatic enhancement in the power conversion efficiency up to 11.6 and 2.1 fold compared to planar structures, for Ta and W thermal emitters, respectively. These numerical findings and underlying physics will provide valuable design strategies to thermal radiation engineered applications such as solar absorbers, radiative coolers, as well as thermophotovoltaics.

      PubDate: 2017-04-29T19:40:29Z
       
  • Fe-based multifunctional nanoparticles with various physicochemical
           properties
    • Abstract: Publication date: August 2017
      Source:Current Applied Physics, Volume 17, Issue 8
      Author(s): Junyoung Kwon, Xiang Mao, Jaebeom Lee
      Over the past few decades, many studies have assessed Fe-based nanoparticles because of their high earth abundance, inexpensive precursors, unique optical properties, electromagnetic nature, biocompatibility, and interactivity with cells. By controlling the composition of a composite, the morphology, size, physical properties, and related functionalities, the synthesized nanomaterials can be altered for specific applications. This review introduces several methods for synthesizing iron-based binary/ternary chalcogenides, iron-based bimetallic materials, and iron-based magnetoplasmonic materials with a range of properties. Furthermore, assembled nanostructures make it possible for us to use these building blocks for broader and customized applications depending on their controlled arrangement. This will facilitate the potential application of iron-based functional materials in spintronics, biomedicine, electronics, and catalysis.
      Graphical abstract image

      PubDate: 2017-04-29T19:40:29Z
       
  • High alcohol-soluble MoOx gel for interfacial layer in organic solar cells
    • Abstract: Publication date: August 2017
      Source:Current Applied Physics, Volume 17, Issue 8
      Author(s): Jian Xiong, Zhen He, Shiping Zhan, Bingchu Yang, Xiaowen Zhang, Ping Cai, Cong Xu, Xiaogang Xue, Jian Zhang
      Water-free solvent soluble, low-temperature processed metal oxides are important for preparing efficient and stable electronic devices, as well as the convenience in simplifying the device production process. Here we reported a facile approach with the features of low-temperature and solution-based process for the formation of a MoOx (s-MoOx) film as interface layer in polymer solar cells (PSCs). The absorbability, elementary composition, electronic property and surface microstructure of the s-MoOx are investigated in detail by ultraviolet–visible spectrophotometer (UV–vis), X-ray photoelectron spectrometry (XPS), ultraviolet photo-electron spectrometer (UPS) and atomic force microscopy (AFM). These investigations confirmed that such MoOx xerogel has high solubility in the organic alcohol solvents, such as ethanol and methanol. Meanwhile, this s-MoOx can be applied as the interfacial layer in organic solar cells via a low-temperature treatment (about 100 °C) due to its proper physical properties, and a power conversion efficiency (PCE) over 3% was achieved. In addition, the devices with s-MoOx shows excellent air-stability, and the PCE efficiency can maintain about 84% of its initial value after 100 h exposure in air, which is dramatically enhanced comparing with the common devices with PEDOT:PSS layer.

      PubDate: 2017-04-29T19:40:29Z
       
  • Calculated structural and electronic interactions of the nano dye molecule
           Ru(4,4´−COOH−2,2´−bpy)2(NCS)2(N3) with a iodide/triiodide redox
           shuttle
    • Abstract: Publication date: August 2017
      Source:Current Applied Physics, Volume 17, Issue 8
      Author(s): E. Shomali, I. Abdolhosseini Sarsari, S. Javad Hashemifar, M. Alaei
      In this paper, dye sensitized solar cell based on nano dye molecule N3 are investigated by using density functional computations. The main focus is on the N3 dye molecule and corresponding complexes formed at the interface between electrolyte and dye, during the regeneration process. The optimized geometry and electronic structure of the molecule and complexes are calculated by using the pseudo-potential as well as full-potential techniques. The absorption spectra of metalliferous dye molecule, N3, and its complexes are computed in the framework of time dependent density functional theory. We determine the reaction path of dye regeneration by Nudged Elastic Band (NEB) method. IR spectrum of the N3 dye molecule were also calculated. We found that complexes of N3 dye molecule and transition states formed in reactions, are magnetic.

      PubDate: 2017-04-29T19:40:29Z
       
  • The study of electronic, magnetic, magneto-optical and thermoelectric
           properties of XCr2O4 (X = Zn, Cd) through modified Becke and Johnson
           potential scheme (mBJ)
    • Abstract: Publication date: August 2017
      Source:Current Applied Physics, Volume 17, Issue 8
      Author(s): Shahid M. Ramay, M. Hassan, Q. Mahmood, Asif Mahmood
      The electronic structure is analyzed to elucidate the magnetic and optical characters and the thermoelectric response of XCr2O4 (X = Zn, Cd) stabilized in the cubic phase by using DFT based FP-LAPW method. The modified Becke–Johnson (mBJ) functional is utilized to compute precise band structures (BS) and density of states (DOS), which confirm ferromagnetic semiconducting behavior. The origin of ferromagnetism explored by computing crystal field energy ( Δ C F ) , John-Teller energy ( Δ J T ) and exchange splitting energies Δ E X ( d ) and Δ E X ( p d ) . It is found that strong hybridization results in decay in Cr the magnetic moment and creates the magnetic moments at the nonmagnetic sites. The optical parameters reveal the suitability for energy harvesting devices. Finally, the BoltzTraP code has been implemented to study the thermoelectric properties, which show that increase in temperature increases the electrical conductivity, thermal conductivity and the power factor, while Seebeck coefficient reduces. Hence, the studied compounds are also suitable for thermoelectric devices to realize useful alternative energy sources.

      PubDate: 2017-04-29T19:40:29Z
       
  • Significant enhancement of resonance magnetoelectric coupling in
           miniaturized lead-free NiFe2O4–BaTiO3 multilayers
    • Abstract: Publication date: August 2017
      Source:Current Applied Physics, Volume 17, Issue 8
      Author(s): Deepak Rajaram Patil, Yi Sheng Chai, June-Hee Kim, Joong-Hee Nam, Jeong-Ho Cho, Byung-Ik Kim, Kee Hoon Kim
      With increasing demands toward device miniaturization, Pb-free magnetoelectric laminates (MELs) with a small lateral dimension of ∼3 × 3 mm2 have been synthesized by the tape-casting method. The MELs are composed of alternating layers of magnetostrictive NiFe2O4 and piezoelectric BaTiO3 with a uniform single layer thickness of t = 50 and 15 μm, respectively. Both laminates exhibit much larger longitudinal ME voltage coefficient α E33 than the transverse ME voltage coefficient α E31 at both off-resonant and resonant frequencies, which is attributed to the preferential easy-plane alignment of the magnetic moments. Furthermore, enhancement in α E33 by more than 5 times has been achieved upon decreasing t from 50 to 15 μm in both resonance and off-resonance conditions. The enhanced α E33 values indicate that nearly ideal interface coupling between the ferromagnetic and piezoelectric layers is realized in the miniaturized, thinner MEL, pointing to practical application potential towards developing mass-produced, low-cost ME devices.

      PubDate: 2017-04-29T19:40:29Z
       
  • The preparation, performance and lithiation mechanism of cobalt-doped zinc
           oxide as a high performance anode material for LIB
    • Abstract: Publication date: August 2017
      Source:Current Applied Physics, Volume 17, Issue 8
      Author(s): Yue Li, WanWan Li, Minhua Fang, XiaoLin Yao, Chao Chen, Miao Shui, Jie Shu, Yuanlong Ren
      Zn1-x Co x O (0 ≤ x ≤ 0.15) anode material was prepared by an easy polyacrylamide assisted sol-gel route. The successful replacement of Zinc by Cobalt within Cobalt content x ≤ 0.09 was confirmed by structural characterization. The introduction of Cobalt element greatly improved the electro-chemical performances of the matrix Zinc oxide. Without carbon coating, at the 20th cycle, Zn0.91Co0.09O anode still preserved a capacity a little bit more than 1000  mA h g−1 and a capacity more than 600  mA h g−1 was retained at the end of the 50th cycle. Better rate capability was also witnessed. The SEM, EIS at OCV, CV and in situ XRD were further carried out to elucidate the lithiation mechanism. The role Cobalt doping played can be summarized as follows: the stabilization of the Li2Zn phase, the minimization of charge transfer resistance and the enhanced reversibility of the reduction from metal oxide to metal.
      Graphical abstract image

      PubDate: 2017-04-29T19:40:29Z
       
  • High photocatalytic efficiency and stability of chromium-indium codoped
           ZnO thin films under sunlight irradiation for water purification
           development purposes
    • Abstract: Publication date: August 2017
      Source:Current Applied Physics, Volume 17, Issue 8
      Author(s): Refka Mimouni, Adel Souissi, Ali Madouri, Karem Boubaker, Mosbah Amlouk
      In this work, we aimed an effective low-cost system for water purification from Methylene Blue using the photocatalytic performance of (Cr,In) codoped ZnO sprayed thin films under sunlight irradiation. XRD analysis demonstrate that the samples crystallized in würtzite ZnO phase, with a privileged orientation of crystallites towards (002) direction parallel to c-axis. The obtained images of AFM and SEM micrographs showed the enhancement of the roughness of ZnO films by codoping. In addition, the optical investigations indicated that the band gap values of (Cr,In) codoped ZnO thin films decreases from 3.3 eV to 3.1 eV in terms of (Cr, In) contents, whence, more solar energy can be exploited for photocatalytic reactions. Likewise, from PL study, the decrease of UV intensity peak by codoping points out the recombination inhibition in ZnO thin films. Also, the presence of defects demonstrated by visible emission has an important role in photocatalysis because on the surface of defects, surface redox reactions are taking place. So, they act as active sites of (Cr,In) codoped ZnO photocatalyst. Moreover, the effect of hydroxide OH radicals and the superoxide anion radicals (O2 -) in photocatalytic mechanism for Methylene Blue degradation was discussed. Furthermore, (Cr,In) codoped ZnO thin films showed an excellent photodegradation efficiency under sunlight irradiation and present high recycling performance even after three re-use cycles.
      Graphical abstract image

      PubDate: 2017-04-29T19:40:29Z
       
  • Enhanced tunnel magnetoresistance and electric-field effect in
           CoFeB/MgO/CoFeB perpendicular tunnel junctions with W underlayer
    • Abstract: Publication date: July 2017
      Source:Current Applied Physics, Volume 17, Issue 7
      Author(s): Dae-Hoon Kim, Kyung-Woong Park, Byong-Guk Park
      We investigated the dependence of tunnel magnetoresistance (TMR) and its electric-field effect in CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJ) on different underlayer (UL) materials. We observed enhancements in the TMR ratio and its temperature dependence as well as electric-field effect in MTJs with W UL, as compared to those in MTJs with a conventional Ta UL. This is attributed to better thermal stability of perpendicular magnetic anisotropy (PMA) in W/CoFeB/MgO, which sustains up to 380 °C, compared to that of Ta/CoFeB/MgO which starts to degrade at 270 °C. This demonstrates that the PMA in a CoFeB/MgO structure and its electric-field dependence can be enhanced by the careful selection of underlayer, opening the way for the realization of electric-field effect-driven spintronic devices.

      PubDate: 2017-04-29T19:40:29Z
       
  • Ohmic contact behavior of aluminum-doped zinc oxide with carbon-doped
           p-GaP epilayer for AlGaInP LEDs applications
    • Abstract: Publication date: July 2017
      Source:Current Applied Physics, Volume 17, Issue 7
      Author(s): Ming-Chun Tseng, Dong-Sing Wuu, Chi-Lu Chen, Hsin-Ying Lee, Ray-Hua Horng
      Aluminum-doped zinc oxide (AZO) thin films used for ohmic contact layers on carbon-doped GaP window layers (p-GaP:C) of AlGaInP light-emitting diodes were fabricated and characterized. AZO thin films with different Zn:Al cycle ratios (15:1, 20:1, and 25:1) were deposited on p-GaP:C window layers through atomic layer deposition. The contact characteristics of the AZO thin films on p-GaP:C were considerably changed from Schottky contact to ohmic contact after rapid thermal annealing (RTA) at 350 °C for 1 min. The most favorable specific contact resistance of AZO/p-GaP:C was evaluated using a circular transmission line model as 6.3 × 10−3 Ω/cm2. Angle-resolved X-ray photoelectron spectroscopy was employed to understand the ohmic contact behavior of AZO/p-GaP:C. After RTA, Zn atoms in the AZO thin films notably diffused into the p-GaP:C layers and Ga atoms diffused out of the p-GaP:C layer. Therefore, the Ga vacancies were occupied by Zn atoms, which increased the doping concentration in the near-surface region of p-GaP:C and reduced the depletion region width of the semiconductor region. Thus, numerous carriers were able to tunnel through the reduced Schottky barrier and those carriers produced the ohmic contact behavior between the AZO and p-GaP:C.

      PubDate: 2017-04-29T19:40:29Z
       
  • Real time monitoring of ordering in pentacene films during growth by using
           in-situ infrared spectroscopy
    • Abstract: Publication date: July 2017
      Source:Current Applied Physics, Volume 17, Issue 7
      Author(s): Yunbog Kim, D. Jeon
      By employing the in-situ Fourier transform infrared (FTIR) spectroscopy and curve-fitting, we studied the evolution in the ordering of vacuum-deposited pentacene films. In the FTIR spectra, the thin film and bulk phases appeared at 903.2 cm−1 and 907.2 cm−1, respectively. The misoriented phase was also observed at 904.4 cm−1. The position and the intensity of each phase varied with the film thickness as well as the growth temperature. The results indicated that most of pentacene molecules formed initially the thin film phase until the bulk and misoriented phases began to form at the increased thickness. Our study suggests that FTIR spectroscopy is an effective tool to monitor in real time the ordering of organic films for quality control.

      PubDate: 2017-04-29T19:40:29Z
       
  • Optical properties of Ba0.6K0.4Fe2As2 thin film prepared by pulsed laser
           deposition and subsequent post-annealing process
    • Abstract: Publication date: July 2017
      Source:Current Applied Physics, Volume 17, Issue 7
      Author(s): Seokbae Lee, Yu-Seong Seo, Seulki Roh, Nam Hoon Lee, Won Nam Kang, Jungseek Hwang
      We investigate a unique material system, Ba0.6K0.4Fe2As2 thin film, using the optical spectroscopic technique. The Ba0.6K0.4Fe2As2 thin film was prepared on an Al2O3 (0001) substrate using the pulsed laser deposition (PLD) method and a subsequent post-annealing process. The Ba0.6K0.4Fe2As2 thin film sample shows a much larger residual resistivity as compared to that of a single crystal of the same compound. We applied the well-known multilayer thin film analysis to obtain optical constants of Ba0.6K0.4Fe2As2 thin film layer from the measured reflectance spectra of the Ba0.6K0.4Fe2As2/Al2O3 sample. The overall temperature-dependent optical properties were found to be similar to those of a corresponding single crystal. From our analysis, we also roughly estimated the superfluid density of 3860 cm−1 and the corresponding London penetration depth of 412 nm of the Ba0.6K0.4Fe2As2 thin film. Our results indicate that this Ba0.6K0.4Fe2As2 thin film prepared by PLD does retain some of the intrinsic physical properties of single crystal samples.

      PubDate: 2017-04-29T19:40:29Z
       
  • Electrical and frequency-dependent properties of Au/Sm2O3/n-GaN MIS
           junction with a high-k rare-earth Sm2O3 as interlayer
    • Abstract: Publication date: July 2017
      Source:Current Applied Physics, Volume 17, Issue 7
      Author(s): V. Manjunath, V. Rajagopal Reddy, P.R. Sekhar Reddy, V. Janardhanam, Chel-Jong Choi
      High-k rare-earth samarium oxide (Sm2O3) films are formed on n-GaN surface and analyzed its compositional properties by XPS measurements. XPS results specify that the Sm2O3 films are formed at the interface. Then, the Au/Sm2O3/n-GaN MIS junction is prepared with a Sm2O3 as insulating layer and correlated its electrical properties with the Au/n-GaN MS junction. The MIS junction shows highest barrier height ((0.81 eV (I-V)/1.0 eV (C-V)) for MIS junction than the MS junction (0.68 eV (I-V)/0.90 eV (C-V)). Excellent rectifying property is observed with lowest reverse leakage current and higher barrier height for the MIS junction than the MS junction, implying that the Sm2O3 insulating layer effectively modified the barrier height. The barrier heights determined from I-V, Cheung's, Norde and ΨS –V plot closely matched with each other, suggesting that these techniques are reliable and valid. The estimated interface state density of the MIS junction (1.990 × 1011 cm−2eV−1 (EC-0.82 eV)) is lower than the MS junction (9.204 × 1012 cm−2eV−1 (EC-0.70 eV)), which demonstrates that the Sm2O3 insulating layer performs an important role in lowering the interface state density. The frequency-dependent characteristics of the MS and MIS junctions are discussed in the frequency range of 10 kHz to 1 MHz and found that the determined capacitance values decrease with increasing frequency. The forward I-V characteristic of the MS and MIS junctions reveals the ohmic behavior at low voltage regions and space-charge-limited conduction at higher voltage regions. Results reveal that the reverse leakage current in the studied MS and MIS junctions is controlled by a Poole-Frenkel emission.

      PubDate: 2017-04-29T19:40:29Z
       
  • Alignment of Ag nanoparticles by an external electric field proposed for
           metamaterial applications
    • Abstract: Publication date: July 2017
      Source:Current Applied Physics, Volume 17, Issue 7
      Author(s): Reza Gholipur, Ali Bahari
      The ability to control the DNG properties of metamaterials in the microwave range makes possible many new constructions and practical applications. In addition, since the fabrication of ordered metamaterials with metallic structure arrays is habitually complex, the mass production of these structures is being prevented. For this purpose, a control on spatial structure of random metamaterial at the nanoscale dimensions was performed. Here, we demonstrate the alignment of dispersed Ag nanoparticles subjected to external AC electric field created by quadrupole electrode in refluxing condition at 180 °C. External electric field allows for alignment of the well-dispersed Ag nanoparticles with long-range orientational order. The effects of the AC electric field on the DNG region that obtained in the microwave range can be accompanied with a control on optical performances, even in the plasmonic field for future studies. This achievement provides a new way toward the development of random metamaterial devices.

      PubDate: 2017-04-29T19:40:29Z
       
  • Optical temperature sensing properties of Yb3+/Tm3+ co-doped NaLuF4
           crystals
    • Abstract: Publication date: July 2017
      Source:Current Applied Physics, Volume 17, Issue 7
      Author(s): Lili Tong, Xiangping Li, Ruinian Hua, Lihong Cheng, Jiashi Sun, Jinsu Zhang, Sai Xu, Hui Zheng, Yanqiu Zhang, Baojiu Chen
      Yb3+/Tm3+ and Yb3+/Er3+ co-doped NaLuF4 crystals were synthesized by a facile hydrothermal method. The optical temperature sensing properties of Tm3+ based upon its two thermally coupled energy levels 3F2, 3 and 3H4 were systematically investigated by means of fluorescence intensity ratio (FIR) technique. The 980 nm laser-induced thermal effect on Tm3+ doped NaLuF4 crystals was studied by using Er3+ doped sample as thermal probe. The temperature sensitivity of Tm3+ in NaLuF4: Yb3+/Tm3+ crystals shows a nonlinear dependence on temperature, and the maximum value is about 0.00045 K−1 at 600 K. The accuracy and reliability of the optical thermometry based on Tm3+ in NaLuF4: Yb3+/Tm3+ crystals has been checked by using Yb3+/Er3+ co-doped sample as temperature sensing unit. The results demonstrate that NaLuF4: Yb3+/Tm3+ crystals have good sensing stability and may have potential application for the optical thermometry.
      Graphical abstract image

      PubDate: 2017-04-29T19:40:29Z
       
  • GaSb/InGaAs 2-dimensional hole gas grown on InP substrate for III-V CMOS
           applications
    • Abstract: Publication date: July 2017
      Source:Current Applied Physics, Volume 17, Issue 7
      Author(s): SangHoon Shin, YounHo Park, HyunCheol Koo, YunHeub Song, JinDong Song
      We grew a two-dimensional hole gas (2DHG) system using a GaSb quantum well layer sandwiched by InGaAs layers in Molecular Beam Epitaxy (MBE). The 2DHG quantum well was achieved using a spreading modulation doping method with Be-dopant. The cross-sectional STEM image clearly shows that large dislocations by lattice-mismatch are relaxed in all layers. We confirmed substantial valence and conduction band offsets in the 2DHG by simulated results. The electrical properties were also observed by Hall measurement, indicating a high hole mobility of 653 cm2/Vs and high carrier concentration of 4.3 × 1012/cm2 at RT.

      PubDate: 2017-04-29T19:40:29Z
       
  • Relaxation effects of magnetization modulus and precession axis on damping
           time of precession in L10-ordered FePt alloy film
    • Abstract: Publication date: July 2017
      Source:Current Applied Physics, Volume 17, Issue 7
      Author(s): Ji-Wan Kim, Hyon-Seok Song, Chun-Yeol You, Sung-Chul Shin
      We investigate the relaxation effects of magnetization modulus and precession axis on the damping time of the precession in L10-ordered FePt alloy film using a time-resolved magneto-optical Kerr effect. It is revealed that their fast relaxation processes during the precession bring about the overestimation of the damping time of the precession. We found that this error becomes more significant as the pump intensity increases. We propose that these corrections need to be considered for materials with the fast relaxation dynamics during the precession.

      PubDate: 2017-04-29T19:40:29Z
       
  • Electronic structure and quantum transport properties of boron and
           nitrogen substituted graphene monolayers
    • Abstract: Publication date: July 2017
      Source:Current Applied Physics, Volume 17, Issue 7
      Author(s): Puspitapallab Chaudhuri, Angsula Ghosh, M.S. Gusmão, C. Mota, H.O. Frota
      In this work we use ab initio density functional theory (DFT) and propose three new configurations of substituted graphene monolayers where the carbon atoms are replaced selectively by boron and nitrogen. The stable equilibrium geometries and corresponding structural, electronic and transport properties of the resulting graphene-like BC, NC and BN hexagonal single-atomic-layer compounds are determined. The characteristics of the NC and BC new compounds are found to be metallic. Our proposed boron-nitrogen hexagonal structure behaves as a semiconductor with gap of 0.52 eV, while the h-BN (alternating boron and nitrogen in graphene structure) studied so far widely is typically an insulator or a wide-band semiconductor. The value of electric current in BC structure is found to be higher than that in usual graphene for a given value of the bias voltage.

      PubDate: 2017-04-22T19:27:43Z
       
  • Improved exciton dissociation and charge transport in energetically
           cascaded trilayer organic solar cells
    • Abstract: Publication date: July 2017
      Source:Current Applied Physics, Volume 17, Issue 7
      Author(s): Ji-Won Seo, Sang-Hoon Lee, Jung-Yong Lee
      We demonstrate improved exciton dissociation and charge transport in trilayer organic solar cells (OSCs). The interlayer with an intermediate energy level between the main donor and acceptor levels assists the dissociation of excitons in the charge transfer state (CT) and aids the charge transport by increasing a CT state energy. Additionally, the total absorption of the OSC was increased due to the complementary absorption of the inserted interlayer. Experimentally, when a chloroaluminum phthalocyanine (ClAlPc) layer was inserted between copper phthalocyanine (CuPc) and C60 in a trilayer OSC, the internal quantum efficiency (IQE) was greatly enhanced by 30% in the wavelength range of 350–550 nm. The enhancement of IQE results in an increase of the power conversion efficiency from 1.30% to 1.69%.

      PubDate: 2017-04-16T06:08:52Z
       
  • Design and analysis of a new composite double negative metamaterial for
           multi-band communication
    • Abstract: Publication date: July 2017
      Source:Current Applied Physics, Volume 17, Issue 7
      Author(s): Mohammad Jakir Hossain, Mohammad Rashed Iqbal Faruque, Mohammad Tariqul Islam
      In this paper, a double C-shaped structure of double negative composite metamaterial is designed and depicts in configurations that can capable in a multi-band microwave frequency band. The design has achieved relative negative permeability, relative negative permittivity and relative negative refractive index. Analysis and comparison were done by using four configurations of composite metamaterial such as horizontal 1 × 1 array and vertical 1 × 1 array structures and the horizontal 1 × 1 and vertical 1 × 1 unit-cell configurations. Multi-band operating frequencies namely, S-band, C-band and X-band have been achieved using all configurations. The proposed metamaterial size is 1.2 cm × 1.2 cm × 0.16 cm which includes all geometrical parameters to fit the design inside the substrate area. Computer Simulation Technology (CST) is adopted to investigate this design where an incident electromagnetic wave travelling along the positive z-axis with an E-field polarized along the y-axis. The results of the proposed metamaterial depict multi-band metamaterial response over the frequency span from 1 to 15 GHz. The effective medium ratio of the metamaterial unit-cell is 7.44. Moreover, the results clearly seen that the single-negative and double-negative metamaterial characteristics of the unit-cell and arrays over the multi-band. The dimensions and scattering parameters of the proposed double C-shaped metamaterial are suitable for the S -band, C-band and X-band applications.

      PubDate: 2017-04-16T06:08:52Z
       
  • Electric-field control of magnetic property in perpendicularly magnetized
           Co0.25Pd0.75/PMN-PT heterostructure
    • Abstract: Publication date: July 2017
      Source:Current Applied Physics, Volume 17, Issue 7
      Author(s): Ji-Wan Kim, Ju-Hyun Kim, Chun-Yeol You, Sung-Chul Shin
      We report about the electric-field control of magnetic properties in a perpendicularly magnetized Co0.25Pd0.75 film deposited on PMN-PT (lead magnesium niobate-lead titanate) substrate. The effective perpendicular anisotropy coefficient K eff is efficiently tuned via the electric field up to 2 MV/m from 2.5 × 104 to 0.8 × 104 J/m3, which leads to the change of the effective magnetic anisotropy field μ 0 Δ H e f f  = −45 mT. With a time-resolved magneto-optical Kerr effect, we observed the precession frequency change Δf = 0.8 GHz. Our simulation estimates that this value corresponds to Δf = −3 GHz and Δf/f = −0.23 in a scheme of ferromagnetic resonance measurement.

      PubDate: 2017-04-16T06:08:52Z
       
  • Discharge source-dependent variation in the densities of active species in
           the flowing afterglows of N2 RF and UHF plasmas
    • Abstract: Publication date: July 2017
      Source:Current Applied Physics, Volume 17, Issue 7
      Author(s): André Ricard, Jean-Philippe Sarrette, Byungwook Jeon, Yu Kwon Kim
      With a potential application to surface modification of oxide materials in mind, active species in RF and microwave (UHF) N2 afterglows were analyzed in our newly designed flowing reactors. For both plasma systems, discharge of N2 was generated in a long quartz tube with a small diameter (dia. 5–6 mm) and then was directly injected into a chamber with a large diameter of 15–20 cm. The discharge condition was set to be similar between the two systems; the gas pressure, flow rate and the applied power were 6 Torr, 0.6 slm and 100 W, respectively. Under this condition, the residence time at the chamber inlet was (1–3) x 10−3 s. The RF and UHF afterglows were formed in the chamber with luminous jets from the end of the discharge tube. However, we found that the densities of active species were quite source-dependent; N and N2(A) densities were higher in UHF than in RF in spite of more O-atoms impurity. The origin of such difference is also attributed to the inherent difference in the nature of excitation between the two plasma sources; RF is more vibrational and is longer than UHF.

      PubDate: 2017-04-16T06:08:52Z
       
  • Exchange couplings calculation in Sr2CrNO6 (N = Os, Ir) Double
           Perovskites: Monte Carlo simulation
    • Abstract: Publication date: July 2017
      Source:Current Applied Physics, Volume 17, Issue 7
      Author(s): O. El Rhazouani, A. Slassi, Y. Ziat, A. Benyoussef
      Exchange couplings in Sr 2 CrNO 6 (N = Os, Ir) Double Perovskites (DPs) have been calculated numerically by using a Monte Carlo Simulation (MCS) in the frame work of Ising model by means of a relation between internal energy per site and magnetization per site. Two model parameters α and α ' have been proposed for Sr 2 CrOsO 6 and Sr 2 CrIrO 6 , respectively. The exchange couplings have been computed by varying α and α ' through a MCS to find their values corresponding to the transition temperature 725K specific to Sr 2 CrOsO 6 and 884 K specific to Sr 2 CrIrO 6 . The exchange couplings J C r − O s = − 35.201 m e V , J C r − C r = 5.452 m e V and J O s − O s = 14.873 m e V have been obtained for Sr 2 CrOsO 6 , while J C r − I r = − 24.464 m e V , J C r − C r ' = 2.181 m e V and J I r − I r = 16.730 m e V have been obtained for Sr 2 CrIrO 6 . Magnetization and magnetic susceptibility have been investigated in both compounds. Internal energy per site has been given.

      PubDate: 2017-04-16T06:08:52Z
       
  • All-dielectric planar solar cells with multilayer ARC and non-periodic DBR
           nanolayers based on transmission line equivalent circuit
    • Abstract: Publication date: Available online 8 April 2017
      Source:Current Applied Physics
      Author(s): Mohammad Reza Salehi, Mojtaba Shahraki, Ebrahim Abiri
      In this paper, an analytical approach based on transmission line equivalent circuit (TLEC) is used to model planar solar cells. The proposed method has been applied to the all-dielectric planar solar cells with multilayer anti-reflection coating (ARC) and non-periodic distributed Bragg reflector (DBR) nanolayers. This analytical approach is very efficient and easy to be implemented. Consequently, it is straightforward to employ several optimization procedures to determine the optimum thickness for different layers. In this paper, optimization process according to the Fuzzy adaptive modified particle swarm optimization (FAMPSO) algorithm is utilized to maximize the absorption enhancement of these types of solar cells. Results demonstrate the possibility of wideband absorption in all-dielectric planar solar cells and comparable to the conventional light trapping structures.

      PubDate: 2017-04-09T06:25:18Z
       
  • Structurally tunable reflective metamaterial polarization transformer
           based on closed fish-scale structure
    • Abstract: Publication date: Available online 22 March 2017
      Source:Current Applied Physics
      Author(s): Xu Zhang, Zeyong Wei, Yuancheng Fan, Limei Qi
      A reflective metamaterial polarization transformer (RMPT) is proposed with closed fish-scale structure for high efficient cross-polarization reflection. The maximum efficiency of cross-polarization reflection for normal incidence is 97.2%. The RMPT maintains good performance for incident angles up to 25°, and the RMPT is not restricted to a specific polarization state of the incident wave. Furthermore, the designed RMPT shows excellent structural tunability by optimizing the structural parameters, which make it user-friendly.

      PubDate: 2017-03-25T06:05:08Z
       
  • Effect of ytterbium, gold and aluminum transparent metallic substrates on
           the performance of the Ga2S3 thin film devices
    • Abstract: Publication date: Available online 21 March 2017
      Source:Current Applied Physics
      Author(s): S.R. Alharbi, A.F. Qasrawi
      In the current work, the structural, optical, dielectric and electrical properties of the Ga2S3 thin films which are deposited onto transparent thin Al, Yb and Au metal substrates are characterized by means of transmittance electron microscopy, X-ray diffraction, ultraviolet–visible light spectroscopy and impedance spectroscopy techniques. The effects of the metallic substrates on the crystalline nature, energy band gap and dielectric spectra are also investigated. The modeling of the dielectric spectra allowed determining the effect of the Al, Yb and Au thin layers on the electron scattering time, the plasmon frequency, free electron density and drift mobility. In addition, a Yb/Ga2S3/Au Schottky barrier and Al/Ga2S3/Au back to back Schottky barrier devices (metal-semiconductor-metal (MSM) device) are fabricated and characterized by means of capacitance -voltage characteristics and capacitance and conductance spectra in the frequency range of 10–1800 MHz. While the Schottky barrier device displayed three distinct positions of resonance-antiresonance phenomena, the MSM device displayed one peak with narrow bandwidth of 10 MHz. The MSM devices exhibited an inversion, depletion and accumulation modes within a voltage range of 0.25 V width at 250 MHz. The study indicates the applicability of these device as smart capacitive switches, as Plasmon devices and as wavetraps.

      PubDate: 2017-03-25T06:05:08Z
       
  • Growth and characterization of single InGaN quantum well in nonpolar
           a-plane (112¯0) InGaN/GaN light-emitting diodes
    • Abstract: Publication date: Available online 20 March 2017
      Source:Current Applied Physics
      Author(s): Kyuhyun Bang, Sukkoo Jung, Kwang Hyeon Baik, Jae-Min Myoung
      We studied the In incorporation efficiency and composition distribution in a nonpolar a-plane InGaN (a-InGaN) quantum well (QW) layer. The In compositions decreased with increasing growth temperatures due to increased In desorption from InGaN surfaces. It was clear that the In incorporation efficiency on a nonpolar GaN surface is lower than that on a polar c-plane GaN. In addition, the In incorporation rate on an a-InGaN layer could be increased by decreasing the V/III ratio without lowering the growth temperature. In the case of the a-InGaN layer, a composition pulling effect was also observed, suggesting that the In composition of the a-InGaN layer increases along the normal growth direction from the bottom to the top of the InGaN QW layer. Using high-resolution XRD 2θ-ω scans, we found that there existed convex graded In compositions ranging from 4 to 12.7% in an a-InGaN QW layer along the growth direction. No wavelength shift with a current injection of 20–100 mA confirmed the absence of a polarization field. The shift in the electroluminescence (EL) peak energy was ∼11 meV between the electric field parallel and perpendicular to the c-axis components, which was caused by the valence band splitting due to the in-plane compressive strain of the 10 nm a-InGaN QW layer. The EL polarization anisotropy was clearly observed with a polarization ratio of 55%.

      PubDate: 2017-03-25T06:05:08Z
       
  • Electrochemical properties of TiO2-metal oxide composites for
           dye-sensitized solar cell
    • Abstract: Publication date: Available online 18 March 2017
      Source:Current Applied Physics
      Author(s): Hyeong Ryeol Baek, Ik Soo Eo
      The several types of nanofibers were added in dye-sensitized solar cells (DSSCs) and there electrochemical properties were investigated. The surface morphologies of TiO2 electrode was studied by field emission scanning electron microscopy (FE-SEM) and the photoelectrochemical properties of the DSSCs were measured by photovoltaic-current density, AC impedance. By adding the several types of nanofibers we successfully increased the amount of dye loading and enhance the solar conversion efficiency. The pure TiO2 film based DSSC was obtained solar conversion efficiency of 4.8% under irradiation of AM 1.5 (100 mWcm−2). The solar energy conversion efficiency of TiO2 film with 5 wt% SiO2 fiber is 6.2% and it's higher than another fiber (ZrO2, Al2O3 and TiO2). The V oc , J sc , and FF are 0.73 V, 14.23 mA cm−2 and 60%, respectively.

      PubDate: 2017-03-25T06:05:08Z
       
  • High-Tc superconductivity from an atomic point of view via tunneling
    • Abstract: Publication date: Available online 18 March 2017
      Source:Current Applied Physics
      Author(s): Jung Hoon Yoo, Jinho Lee
      Even after 30 years of discovery of the high temperature superconductivity (HTSC) from the cuprate compounds by Bednorz and Müller, the mechanism of the formation of Cooper pairs well above the liquid nitrogen boiling temperature is still remained to be elucidated. The discovery of a yet another HTSC family of the iron-based superconductors seemed to add more complexity to this puzzle, but also seems to render a prospect of finding a universal principle shared by the entire HTSC family. The tunneling experiments, on the other hand, also witnessed remarkable breakthroughs ever since Giaever succeeded the first tunneling experiment on a superconducting aluminum. The scanning tunneling microscopy (STM) invented by Binnig and Rohrer began to be heavily applied to the research of the condensed matter and became one of the most versatile spectroscopic tools as well as the most powerful microscope available also in the HTSC research field as of today. In this review, we would like to convey a snapshot of the current application of the STM in the research of HTSC, mainly focusing on the studies using the spectroscopic imaging scanning tunneling microscopy (SI-STM) which eventually led to the scanning Josephson tunneling microscopy (SJTM) by which we can visualize the superconducting Cooper pairs in an atomic scale.

      PubDate: 2017-03-25T06:05:08Z
       
  • Ruthenium doped carbon aerogel with CO2 surface activation for enhanced
           electrochemical capacitance
    • Abstract: Publication date: Available online 18 March 2017
      Source:Current Applied Physics
      Author(s): Ashish Singh, D.K. Kohli, Sushmita Bhartiya, Rashmi Singh, M.K. Singh, P.K. Gupta
      With the aim of enhancement of electrochemical capacitance, CO2 activation of carbon aerogel (CA) prepared by polycondensation of resorcinol with formaldehyde was performed to obtain activated carbon aerogel (ACA) having improved surface area properties. Ruthenium oxide nano-particles were loaded by impregnation method for utilizing pseudo-capacitive property of ruthenium oxide (RuO2) and the effect of activation treatment was studied. RuO2 loading of 20% by weight was accomplished in CA and ACA to synthesize RuO2 doped carbon aerogel (CA/RuO2) and activated carbon aerogel (ACA/RuO2). While the specific capacitance of carbon aerogel improved from 95 to 153 F/g on activation, RuO2 loading further led to enhancement in capacitance and specific capacitance of 308 F/g was obtained for ACA/RuO2. The studies being important for Ru economy, showed the influence of surface area enhancement of base matrix in achieving high specific capacitance.

      PubDate: 2017-03-25T06:05:08Z
       
  • Anomalously high dielectric strength and low frequency dielectric
           relaxation of a bent-core liquid crystal with a large kink angle
    • Abstract: Publication date: Available online 16 March 2017
      Source:Current Applied Physics
      Author(s): Anoop Kumar Srivastava, Jongyoon Kim, Sunggu Yeo, Jinyoung Jeong, E-Joon Choi, Vijay Singh, Ji-Hoon Lee
      We investigated the dielectric dispersion property of a bent-core liquid crystal (BLC) with a large kink angle in the frequency range of 1.0 Hz–5.5 MHz in a planar aligned cell. Single dielectric dispersion was observed in the smectic A, nematic, and isotropic phase of the planar aligned sample. The dielectric strengths, relaxation frequencies, distribution parameters, and dc conductivity were measured as a function of temperature. The dielectric strength of the observed relaxation mode was anomalously high (∼70), whereas the relaxation frequency was low at ∼500 Hz. The relaxation mode observed in the planar aligned cell was attributed to the fluctuations in the polarization direction due to the cooperative motion of the molecules.

      PubDate: 2017-03-18T09:30:56Z
       
  • Prediction of tensile modulus in polymer nanocomposites containing carbon
           nanotubes (CNT) above percolation threshold by modification of
           conventional model
    • Abstract: Publication date: Available online 16 March 2017
      Source:Current Applied Physics
      Author(s): Yasser Zare, Kyong Yop Rhee
      In this paper, a simple model is developed to predict the tensile modulus of polymer/carbon nanotubes (CNT) nanocomposites (PCNT) above percolation threshold. Since the conventional models such as Ouali and Lyngaae-Jorgensen (L-J) cannot predict the accurate results, a developed model is presented which calculates proper modulus as a function of aspect ratio (α) and volume fraction of CNT at percolation threshold ( ϕ p ) . The developed model can present accurate data, which agree with the experimental results at all filler concentrations. The high ranges of “α” and low values of “ ϕ p ” achieve a desirable modulus. However, a high “ ϕ p ” causes the poor modulus at different “α” demonstrating that the role of “α” is highlighted at slight “ ϕ p ”. It is also possible to calculate the “α” and “ ϕ p ” parameters by applying the developed model to the experimental data of modulus.

      PubDate: 2017-03-18T09:30:56Z
       
  • Multiferroic effect of multilayer low-distorted doped bismuth ferrite thin
           films as a function of sputtering power and crystallographic texture
    • Abstract: Publication date: Available online 16 March 2017
      Source:Current Applied Physics
      Author(s): G. Rojas-George, A. Concha-Balderrama, H. Esparza-Ponce, J.J. Gervacio-Arciniega, M.P. Cruz, V. Orozco-Carmona, A. Reyes-Rojas
      Low-distortion rhombohedral multilayer barium-nickel co-doped BiFeO3 (Bi0.75Ba0.25Fe0.975Ni0.025O3) multiferroic thin films were grown on Pt/TiO2/SiO2/Si substrates by reactive RF magnetron sputtering, as a function of sputtering power. X-ray diffraction showed that Bi0.75Ba0.25Fe0.975Ni0.025O3 multilayer films have a pseudocubic-type structure. Piezoresponse force microscopy demonstrated polarization switching in all films at room temperature. Scanning electron microscopy showed different morphologies depending on the sputtering power used during the deposition process and that the thickness of the film decreases from about 142 nm to 72 nm as the sputtering power decreases. Magnetization results showed that as the thickness of the film decreases, the magnetization of the film increases. Thus, there is a direct relation between the sputtering power, thickness and the magnetization of the film. A direct relation between in-plane residual stress and thin film thickness has been obtained. This causes the main axe of the BO6 octahedra to be tilted from 90 to 45° (from thin-film surface) by a texture crystal volume of 29 and 18% in the (012) and (110) crystallographic planes respectively.
      Graphical abstract image

      PubDate: 2017-03-18T09:30:56Z
       
  • Emission of CdSe quantum dots according to the capping ligands
    • Abstract: Publication date: Available online 9 March 2017
      Source:Current Applied Physics
      Author(s): Min Jung Lee, Jaewon Lee, Ho-Soon Yang, Kyong-Soo Hong
      Quantum dot nanocrystals have particular optical properties due to the quantum confinement effect and the surface effect. This study focuses on the effects of organic materials capping quantum dot on the emission properties of quantum dots. The quantum dots prepared by using 1-hexadecylamine in the synthesis show strong emission, while the quantum dots prepared by using tri-octylphosphine oxide exhibit a suppressed emission and an extra emission related with the surface energy traps. These organic materials cap the quantum dots and make the surface conditions of quantum dots different. TEM images and X-ray diffraction patterns reveal that 1-hexadecylamine constructs a layer on the surface of quantum dot during the synthesis and this surface passivation by a layer of 1-hexadecylamine reduces the surface energy traps. Differently from 1-hexadecylamine, tri-octylphosphine oxide dangles from the surface, which causes a poorly passivated surface. This generates the surface deep trap levels giving rise to a significant and broad emission in the lower energy regime. The optical mechanism is studied by measuring the emission spectra and the time-resolved spectra at various temperatures from 4 K to 300 K.

      PubDate: 2017-03-18T09:30:56Z
       
  • Enhancement of a photovoltaic cell performance by a coupled cooled
           
    • Abstract: Publication date: Available online 9 March 2017
      Source:Current Applied Physics
      Author(s): H. Machrafi
      A new analytical mathematical model is developed, describing a cooled photovoltaic-thermoelectric hybrid system. The thermoelectric material is a nanocomposite where the model takes into account size-dependent non-local thermoelectric properties from an extended thermodynamic point of view. The photovoltaic device powers also the cooling system. The model determines first the optimum thickness of the photovoltaic device, then studies the influence of several size-related parameters on the thermoelectric efficiency (also related to the figure of merit) and finally, coupled to a cooling device, the overall efficiency. For the photovoltaic part, the model is applied to two materials, mono-crystalline and poly-crystalline silicon. The thermoelectric part of the model is applied to an n-leg nanocomposite made out of Sb2Te3 nanoparticles in a Bi2Te3 matrix and of a p-leg nanocomposite made out of Bi2Se3 nanoparticles in a Bi2Te3 matrix. An optimal total photovoltaic device size has been found to be around 127 μm and 1.25 μm for the mono- and poly-crystalline silicon, respectively, leading to efficiencies up to 20%, depending on photovoltaic recombination characteristics. With the cooling device, the overall efficiency was increased by up to an additional 10% (an increase of almost 50%), leading to overall efficiencies around 25%.

      PubDate: 2017-03-18T09:30:56Z
       
 
 
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