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Publisher: Springer-Verlag (Total: 2351 journals)

 Applied Physics A   [SJR: 0.535]   [H-I: 121]   [8 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 0947-8396 - ISSN (Online) 1432-0630    Published by Springer-Verlag  [2351 journals]
• Ultrafast re-structuring of the electronic landscape of transparent
dielectrics: new material states (Die-Met)
• Authors: E. G. Gamaly; A. V. Rode
Abstract: Swift excitation of transparent dielectrics by ultrashort and highly intense laser pulse leads to ultra-fast re-structuring of the electronic landscape and generates many transient material states, which are continuously reshaped in accord with the changing pulse intensity. These unconventional transient material states, which exhibit simultaneously both dielectric and metallic properties, we termed here as the ‘Die-Met’ states. The excited material is transparent and conductive at the same time. The real part of permittivity of the excited material changes from positive to negative values with the increase of excitation, which affects strongly the interaction process during the laser pulse. When the incident field has a component along the permittivity gradient, the amplitude of the field increases resonantly near the point of zero permittivity, which dramatically changes the interaction mode and increases absorption in a way that is similar to the resonant absorption in plasma. The complex 3D structure of the permittivity makes a transparent part of the excited dielectric (at ε0 > εre > 0) optically active. The electro-magnetic wave gets a twisted trajectory and accrues the geometric phase while passing through such a medium. Both the phase and the rotation of the polarisation plane depend on the 3D permittivity structure. Measuring the transmission, polarisation and the phase of the probe beam allows one to quantitatively identify these new transient states. We discuss the revelations of this effect in different experimental situations and their possible applications.
PubDate: 2018-02-26
DOI: 10.1007/s00339-018-1693-3
Issue No: Vol. 124, No. 3 (2018)

• CdTe quantum-dot-modified ZnO nanowire heterostructure
• Authors: Kanchana Shahi; R. S. Singh; Ajaya Kumar Singh; Mariya Aleksandrova; Rabah Khenata
Abstract: The effect of CdTe quantum-dot (QD) decoration on the photoluminescence (PL) behaviour of ZnO nanowire (NW) array is presented in the present work. Highly crystalline and vertically 40–50 nm diameter range and 1 µm in length aligned ZnO NWs are synthesized using low-cost method. The crystallinity and morphology of the NWs are studied by scanning electron microscopy and X-ray powder diffraction methods.Optical properties of the nanowires are studied using photo-response and PL spectroscopy. CdTe QDs are successfully synthesized on ZnO nanowire surface by dip-coating method. ZnO NWs are sensitized with CdTe QDs characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, and PL spectroscopy. The highly quenched PL intensity indicates the charge transfer at interface between CdTe QDs and ZnO NWs and is due to the formation of type-II heterostructure between QDs and NWs. Photo-response behaviour of heterostructure of the film is also been incorporated in the present work.
PubDate: 2018-02-24
DOI: 10.1007/s00339-018-1688-0
Issue No: Vol. 124, No. 3 (2018)

• Optical properties of Mn-doped 0.15Pb(In 1/2 Nb 1/2 )O 3 –0.57Pb(Mg 1/3
Nb 2/3 )O 3 –0.28PbTiO 3 single crystal
• Authors: Yue Li; Yanxue Tang; Feifei Wang; Xiangyong Zhao; Jianwei Chen; Zhou Zeng; Linrong Yang; Haosu Luo
Abstract: The refractive indices, extinction coefficients, and transmittance of 1 mol% Mn-doped 0.15Pb(In1/2Nb1/2)O3–0.57Pb(Mg1/3Nb2/3)O3–0.28PbTiO3 (Mn-PIN–PMN–PT) relaxor-based single crystal were investigated. The Mn-PIN–PMN–PT single crystal exhibited a rhombohedral to tetragonal phase transition temperature Trt of 120.3 °C and Curie temperature TC of 152.4 °C. The improved Sellmeier equation for the refractive index was determined by least-squares method, which can be applied to calculate accurately the refractive index over a wide wavelength range from 350 to 5000 nm. The Sellmeier optical coefficients were found to be S0 = 1.178 × 1014 m−2, λ0 = 0.215 µm, E0 = 6.06 eV and Ed = 28.73 eV through fitting the single-term oscillator equation. The transmittance reached about 72% over a wide wavelength from 500 nm to 2.5 µm. The optical band-gap energy Eg of 3.34 eV was obtained from absorption coefficient spectra by use of the Tauc model. The results can offer essential parameters of the Mn-PIN–PMN–PT single crystal for optical device applications.
PubDate: 2018-02-23
DOI: 10.1007/s00339-018-1696-0
Issue No: Vol. 124, No. 3 (2018)

• Frequency- and doping-level influence on electric and dielectric
properties of PolySi/SiO 2 /cSi (MOS) structures
• Authors: N. Doukhane; B. Birouk
Abstract: The electric and dielectric characteristics of PolySi/SiO2/cSi (MOS) structure, such as series resistance (Rs), dielectric constants (ɛ′) and (ɛ″), dielectric losses (tan δ), and the ac electric conductivity (σac), were studied in the frequency range 100 kHz–1 MHz for various doping levels and two thicknesses for the polysilicon layer (100 and 175 nm). The experimental results show that the C and G/ω characteristics are very sensitive to the frequency due to the presence of interface states. Series resistance Rs is deduced from C and G/ω measurements and is plotted as a function of the frequency for various doping levels. It is found to decrease with frequency and doping level. To determine $$~{\varepsilon ^\prime }$$ , ε″, tan δ, and $${\sigma _{{\text{ac}}}}$$ , the admittance technique was used. An interesting behavior of the constants, $$~{\varepsilon ^\prime }$$ and ε″, was noticed. The $$~{\varepsilon ^\prime }$$ values fit led to relations between $$~{\varepsilon ^\prime }$$ and the frequency, on one hand, and between $$~{\varepsilon ^\prime }$$ and the electric conductivity of the polysilicon layers on the other. These relations make it possible to interpolate directly between two experimental points for a given frequency. The analysis of the results shows that the values of $$~{\varepsilon ^\prime }$$ , ε″, and tan δ decrease with increasing frequency. This is due to the fact that in the region of low frequencies, interfacial polarization occurs easily, and the interface states between Si and SiO2 contribute to the improvement of the dielectric properties of the PolySi/SiO2/cSi structures. The study also emphasizes that the ac electric conductivity increases with the increase in frequency and doping level; this causes to the reduction in series resistance.
PubDate: 2018-02-23
DOI: 10.1007/s00339-018-1684-4
Issue No: Vol. 124, No. 3 (2018)

• Correction to: Electrical and optical characterizations of InAs/GaAs
quantum dot solar cells
• Authors: Im Sik Han; Seung Hyun Kim; Jong Su Kim; Sam Kyu Noh; Sang Jun Lee; Honggyun Kim; Deok-Kee Kim; Jae-Young Leem
Abstract: The original version of this article unfortunately contained a mistake. The spelling of the 6th author was incorrect. The correct name is Honggyun Kim.
PubDate: 2018-02-22
DOI: 10.1007/s00339-018-1695-1
Issue No: Vol. 124, No. 3 (2018)

• InP/ZnS quantum-dot-dispersed nematic liquid crystal illustrating
characteristic birefringence and enhanced electro-optical parameters
• Authors: Aradhana Roy; Govind Pathak; Jakub Herman; Sanjeev R. Inamdar; Atul Srivastava; Rajiv Manohar
Abstract: The present study investigates the influence of InP/ZnS core/shell QDs on various parameters of Nematic LC sample 1832A, based on 4-(4-alkyl-cyclohexyl)benzene isothiocyanates and 4-(4-alkyl-cyclohexyl)biphenyl isothiocyanates. Observations recorded consist of distinguished functioning of birefringence phenomenon along with characteristic response time measurement. Further study of rotational viscosity and splay elastic constant portrays stupendous behavior strengthening the appositeness of the composites for low-charge consumable devices. The addition of 0.2 ml of core/shell QDs producing more than two times faster response and enhanced birefringence at low-temperature range can be employed in development of thermostable photonic devices. In addition, dielectric properties comprising of relative permittivity and conductivity have been reported supporting the outcome of the investigation in applicative LC-based technologies.
PubDate: 2018-02-22
DOI: 10.1007/s00339-018-1678-2
Issue No: Vol. 124, No. 3 (2018)

• Magneto-transport and magneto-optical studies on SnO 2 transparent
semiconducting thin films alloyed with Mn over a wide range of
concentration
• Authors: M. M. Bagheri Mohagheghi; Sh. Tabatabai Yazdi; M. Mousavi
Abstract: In this work, Mn-alloyed tin oxide transparent thin films with different Mn concentrations up to 60 at% were prepared via the spray pyrolysis method, and their structural, magneto-optical, and magneto-transport properties were studied. The results show that all the deposited films are polycrystalline with the tetragonal rutile structure. The unit cell volume of Sn1−xMn x O2 films was found to be minimum at the Mn concentration of x = 0.15 indicating to two different mechanisms for Mn addition in the crystal lattice of tin oxide. For the films with Mn concentrations less than 15%, substitutional doping is the working mechanism, while for more Mn concentrations, interstitial one is predominant. A critical Mn concentration about that observed for the structural properties of the films (i.e., x = 0.15) was revealed for their magnetoresistance and magneto-optical properties, as well. This suggests a correlation between the structural and magnetic behaviors of the deposited SnO2:Mn films.
PubDate: 2018-02-22
DOI: 10.1007/s00339-018-1685-3
Issue No: Vol. 124, No. 3 (2018)

• Study on fibre laser machining quality of plain woven CFRP laminates
• Authors: Maojun Li; Shuo Li; Xujing Yang; Yi Zhang; Zhichao Liang
Abstract: Laser cutting is suitable for large-scale and high-efficiency production with relatively high cutting speed, while machining of CFRP composite using lasers is challenging with severe thermal damage due to different material properties and sensitivity to heat. In this paper, surface morphology of cutting plain woven carbon fibre-reinforced plastics (CFRP) by fibre laser and the influence of cutting parameters on machined quality were investigated. A full factorial experimental design was employed involving three variable factors, which included laser pulse frequency at three levels together with laser power and cutting speed at two levels. Heat-affected zone (HAZ), kerf depth and kerf angle were quantified to understand the interactions with cutting parameters. Observations of machined surface were analysed relating to various damages using optical microscope and scanning electron microscopy (SEM), which included HAZ, matrix recession, fibre protruding, striations, fibre-end swelling, collapses, cavities and delamination. Based on ANOVA analysis, it was found that both cutting speed and laser power were significant factors for HAZ and kerf depth, while laser power was the only significant factor for kerf angle. Besides, HAZ and the kerf depth showed similar sensitivity to the pulse energy and energy per unit length, which was opposite for kerf angle. This paper presented the feasibility and experimental results of cutting CFRP laminates using fibre laser, which is possibly the efficient and high-quality process to promote the development of CFRPs.
PubDate: 2018-02-22
DOI: 10.1007/s00339-017-1538-5
Issue No: Vol. 124, No. 3 (2018)

• Unusual effects of manual grinding and subsequent annealing process
observed in Gd 5.09 Ge 2.03 Si 1.88 compound
• Authors: A. M. G. Carvalho; C. S. Alves; P. V. Trevizoli; A. O. dos Santos; S. Gama; A. A. Coelho
Abstract: The Gd5.09Ge2.03Si1.88 compound, as well as other magnetocaloric materials, certainly will not be used in their un-manufactured as-cast condition in future magnetic refrigeration applications or other devices. In this work, we have studied the Gd5.09Ge2.03Si1.88 compound processed in different ways, mainly, the as-cast powder, the annealed powder, and the pressed and sintered powder. The annealed powder (1370 K/20 h) does not present the monoclinic phase and the first-order magneto-structural transition observed in the as-cast powder. The pressed and sintered powder also do not present the first-order transition. Furthermore, the compacting pressure shifts the second-order magnetic transition to lower temperatures. The behavior of cell parameters as a function of the compacting pressure indicates that TC is directly affected by parameter c change.
PubDate: 2018-02-22
DOI: 10.1007/s00339-018-1690-6
Issue No: Vol. 124, No. 3 (2018)

• Cell damage evaluation of mammalian cells in cell manipulation by
amplified femtosecond ytterbium laser
• Authors: Z.-Y. Hong; T. Iino; H. Hagihara; T. Maeno; K. Okano; R. Yasukuni; Y. Hosokawa
Abstract: A micrometer-scale explosion with cavitation bubble generation is induced by focusing a femtosecond laser in an aqueous solution. We have proposed to apply the explosion as an impulsive force to manipulate mammalian cells especially in microfluidic chip. Herein, we employed an amplified femtosecond ytterbium laser as an excitation source for the explosion and evaluated cell damage in the manipulation process to clarify the application potential. The damage of C2C12 myoblast cell prepared as a representative mammalian cell was investigated as a function of distance between cell and laser focal point. Although the cell received strong damage on the direct laser irradiation condition, the damage sharply decreased with increasing distance. Since the threshold distance, above which the cell had no damage, was consistent with radius of the cavitation bubble, impact of the cavitation bubble would be a critical factor for the cell damage. The damage had strong nonlinearity in the pulse energy dependence. On the other hand, cell position shift by the impact of the cavitation bubble was almost proportional to the pulse energy. In balance between the cell viability and the cell position shift, we elucidated controllability of the cell manipulation in microfluidic chip.
PubDate: 2018-02-22
DOI: 10.1007/s00339-018-1677-3
Issue No: Vol. 124, No. 3 (2018)

• Synthesis of homogeneous CaMoO 4 microspheres with nanopits for
high-capacity anode material in Li-ion battery
• Authors: Jiangfeng You; Ling Xin; Xiao Yu; Xiang Zhou; Yong Liu
Abstract: Homogeneous CaMoO4 microspheres with interesting nanopit morphology were prepared by a simple one-step hydrothermal method. These microspheres had a very promising alternative structure for application in Li-ion batteries (LIBs), because they combined the advantages of both the primary nanosized and secondary microsized structures. The nanopits distributed on CaMoO4 material can accommodate volume change, increase their contacting surface and wetting property with electrolyte, and improve wetting contact between CaMoO4 material and electrolyte, leading to enhanced cycling stability and electrochemical performance. Meanwhile, the robust microsphere structure can both prevent aggregation and provide high tap density. When used as an anode in LIBs, the electrodes delivered a high discharge capacity of 434 mAh/g after 50 charge–discharge cycles at a current density of 200 mA/g, showing good cycling performance.
PubDate: 2018-02-22
DOI: 10.1007/s00339-018-1689-z
Issue No: Vol. 124, No. 3 (2018)

• Photo- and thermally induced property change in Ag diffusion into Ag/As 2
Se 3 thin films
• Authors: Adyasha Aparimita; C. Sripan; R. Ganesan; Ramakanta Naik
Abstract: In the present report, we have prepared As2Se3 and bilayer Ag/As2Se3 chalcogenide thin films prepared by thermal evaporation process. The top Ag layer is being diffused into the bottom As2Se3 layer by 532 nm laser irradiation and thermal annealing process. The photo and thermal energy drives the Ag+ ions into the As2Se3 matrix that enhances the formation of As–Se–Ag solid solution which shows the changes of optical properties such as transmission, absorption power, refractive index, and optical band gap. The transmission power drastically decreased for the thermal-induced film than the laser induced one; and the reverse effect is seen for the absorption coefficient. The non-linear refractive index is found to be increased due to the Ag diffusion into As2Se3 film. The indirect allowed optical band gap is being reduced by a significant amount of 0.17 eV (thermal diffusion) and 0.03 eV (photo diffusion) from the Ag/As2Se3 film. The Ag diffusion creates chemical disorderness in the film observed from the two parameters which measures the degree of disorder such as Urbach energy and Tauc parameter. The structural change is not noticed in the studied film as seen from the X-ray diffraction pattern. Scanning electron microscopy and atomic force microscopy investigations showed that the surface morphology was influenced by the diffusion phenomena. The change in optical constants in such type of film can be used in optical waveguides and optical devices.
PubDate: 2018-02-22
DOI: 10.1007/s00339-018-1692-4
Issue No: Vol. 124, No. 3 (2018)

• The structure and mechanical properties of AlMg5Si2Mn alloy after surface
alloying by the use of fiber laser
• Authors: Wojciech Pakieła; Tomasz Tanski; Mirosława Pawlyta; Katarzyna Pakieła; Zbigniew Brytan; Marek Sroka
Abstract: Laser surface treatment is successfully applied to increase hardness as well as corrosion and wear resistance in light alloys such as aluminum or magnesium. The laser surface remelting also can be used to repair superficial cracks, voids or porosity caused by the mechanical impact, metallurgical process as well as the corrosive environment on the surface of the aluminum alloy. The purpose of this paper was to investigate the influence of a fiber laser surface treatment on the structure and properties of the EN AC AlMg5Si2Mn alloy. The goal of this investigation was to increase the hardness and improve tribological properties of the aluminum alloy surface as a result of the conducted laser surface treatment. During laser processing, the top surface of the aluminum alloy was enriched with Cr and Ni particles. The grain size of the applied particles was approximately about 60–130 m. The Cr–Ni powder has been introduced in the molten pool using vacuum feeder at a constant rate of 4.5 g/min. For surface remelting we used square laser beam at a size 3 × 3 mm and with the power of 3.0 kW. The linear laser scan rate of the beam was set at 0.5 m/min. Argon was used to protect the liquid metal alloy during surface treatment. Application of the laser treatment on aluminum alloy has enabled to obtain much harder as well as better wear resistant material compared to the untreated EN AC AlMg5Si2Mn.
PubDate: 2018-02-21
DOI: 10.1007/s00339-017-1525-x
Issue No: Vol. 124, No. 3 (2018)

• Performances and impedance spectroscopy of Small-molecule bulk
heterojunction solar cells based on PtOEP: PCBM
• Authors: A. A. Abuelwafa; M. Dongol; M. M. El-Nahass; T. Soga
Abstract: Small-molecule bulk heterojunction (SBHJ) solar cells based on platinum octaethylporphyrin (PtOEP) as donor material and phenyl-C61-butyric acid methyl ester (PCBM) as the acceptor were fabricated using spin coating techniques with weight ratios from 1:0.1 to 1:9. The formation of charge transfer complex CTC in the PtOEP: PCBM blend was specified from the redshift of the PtOEP absorption peak after blending with PCBM. The photovoltaic performance for PtOEP: PCBM blends were investigated using the external quantum efficiency (EQE) besides the current density–voltage (J–V) characteristics under illumination100 mW/cm2 (AM1.5G). The BHJ solar cell with PtOEP: PCBM ratio of 1:9 exhibited the best performance. The impedance spectroscopy (IS) was examined in the frequency range from 25 Hz to 1 MHz. The equivalent circuit model was evaluated in details to evaluate the impedance spectroscopy parameters. Dielectric constant $${\varepsilon ^\prime }$$ , dielectric loss $${\varepsilon ^{\prime \prime }}$$ and dielectric modulus were included and discussed in terms of dielectric polarization processes. Dielectric modulus displays the non-Debye relaxation in PtOEP: PCBM BHJ solar cells.
PubDate: 2018-02-21
DOI: 10.1007/s00339-018-1674-6
Issue No: Vol. 124, No. 3 (2018)

• A new family of carbon materials with exceptional mechanical properties
• Authors: Jiajia Ran; Kunpeng Lin; Haotian Yang; Jianlin Li; Lianjun Wang; Wan Jiang
Abstract: A new family of carbon materials with ultrahigh-strength and nano-onion grains has been successfully produced from nano-diamond particles by spark plasma sintering. It is believed that the spark plasma and applied pressure help overcome the difficulties in densification. Also diamond has a much greater density than that of graphite, leading to the volume expansion when nano-diamond particles transform to graphite onions during heating, facilitating the consolidation. The as-prepared bulk graphite with a density of 1.84 g/cm3 has ultrahigh bending strength, modulus and microhardness, 150 MPa, 31.3 GPa and 2.6 GPa, respectively, due to the unique microstructure of nano-graphite onions.
PubDate: 2018-02-21
DOI: 10.1007/s00339-018-1691-5
Issue No: Vol. 124, No. 3 (2018)

• Influence of annealing on the optoelectronic properties of the GLAD
synthesized SiO x –ZnO heterostructure nanoclusters
• Authors: Rajshree Rajkumari; Naorem Khelchand Singh
Abstract: We utilized Glancing angle deposition (GLAD) technique to synthesize SiO x –ZnO heterostructure nanoclusters. The as deposited heterostructure nanoclusters were annealed at 550 °C for 1 h in an open air using heating and cooling ramp of 5°C min−1. The FEG-SEM image represents the uneven growth of SiO x –ZnO heterostructure nanoclusters. Due to the agglomeration of smaller nanocluster, SiO x –ZnO heterostructure nanoclusters become more prominent after annealing. EDX indicates the presence of O, Si and Zn. The increase in the concentration of oxygen in annealed SiO x –ZnO heterostructure nanoclusters is attributed to the absorption of O2 molecules during an open air annealing. The formation of heterostructure is shown by the TEM image. The nanoclusters consist of SiO x and ZnO indicating the length of ~ 126 and ~ 97 nm, respectively. The SAED pattern depicts the crystalline nature of ZnO nanoclusters. The XRD pattern revealed that ZnO nanoclusters had wurtzite structure with (100), (002) and (101) orientations. The PL emission at 420 nm is ascribed to the radiative recombination of photoexcited electrons in the conduction band (CB) of ZnO and acceptor such as traps present in SiO x . The band gap significantly increases to 3.45 eV after annealing and it corresponds to main band gap of ZnO. The FTIR result shows the bonding of SiO x –ZnO heterostructure nanoclusters. In addition to the above measurement, we determined the I–V characteristics of the as deposited and annealed SiO x –ZnO heterostructure nanoclusters. The as deposited sample shows schottky behavior which is applicable for nanoscale optoelectronic devices whereas the ohmic nature obtained after open air annealing is suitable for the application of solar cells.
PubDate: 2018-02-21
DOI: 10.1007/s00339-018-1687-1
Issue No: Vol. 124, No. 3 (2018)

• Pulse-by-pulse depth profile measurement of femtosecond laser ablation on
copper
• Authors: Shuntaro Tani; Yohei Kobayashi
Abstract: Pulse-by-pulse depth profile measurements were performed during femtosecond laser pulse irradiation on copper. The evolution of the ablation depth and the surface roughness during multi-pulse irradiation was investigated using a three-dimensional microscope. We found that a number of pulse irradiation was required to activate constant-rate ablation and the number of pulses depended on the fluence. We conclude that laser-induced embrittlement of a target material plays a decisive role to determine the ablation rate during multiple-pulse irradiation.
PubDate: 2018-02-21
DOI: 10.1007/s00339-018-1694-2
Issue No: Vol. 124, No. 3 (2018)

• Thermomechanical modelling of laser surface glazing for H13 tool steel
• Authors: I. R. Kabir; D. Yin; N. Tamanna; S. Naher
Abstract: A two-dimensional thermomechanical finite element (FE) model of laser surface glazing (LSG) has been developed for H13 tool steel. The direct coupling technique of ANSYS 17.2 (APDL) has been utilised to solve the transient thermomechanical process. A H13 tool steel cylindrical cross-section has been modelled for laser power 200 W and 300 W at constant 0.2 mm beam width and 0.15 ms residence time. The model can predict temperature distribution, stress–strain increments in elastic and plastic region with time and space. The crack formation tendency also can be assumed by analysing the von Mises stress in the heat-concentrated zone. Isotropic and kinematic hardening models have been applied separately to predict the after-yield phenomena. At 200 W laser power, the peak surface temperature achieved is 1520 K which is below the melting point (1727 K) of H13 tool steel. For laser power 300 W, the peak surface temperature is 2523 K. Tensile residual stresses on surface have been found after cooling, which are in agreement with literature. Isotropic model shows higher residual stress that increases with laser power. Conversely, kinematic model gives lower residual stress which decreases with laser power. Therefore, both plasticity models could work in LSG for H13 tool steel.
PubDate: 2018-02-20
DOI: 10.1007/s00339-018-1671-9
Issue No: Vol. 124, No. 3 (2018)

• Effect of interfacial SiO 2−y layer and defect in HfO 2−x film on
flat-band voltage of HfO 2−x /SiO 2−y stacks for backside-illuminated
CMOS image sensors
• Authors: Heedo Na; Jimin Lee; Juyoung Jeong; Taeho Kim; Hyunchul Sohn
Abstract: In this study, the effect of oxygen gas fraction during deposition of a hafnium oxide (HfO2−x) film and the influence of the quality of the SiO2−y interlayer on the nature of flat-band voltage (Vfb) in TiN/HfO/SiO2−y/p-Si structures were investigated. X-ray photoemission spectroscopy analysis showed that the non-lattice oxygen peak, indicating an existing oxygen vacancy, increased as the oxygen gas fraction decreased during sputtering. From C–V and J–E analyses, the Vfb behavior was significantly affected by the characteristics of the SiO2−y interlayer and the non-lattice oxygen fraction in the HfO2−x films. The HfO2−x/native SiO2−y stack presented a Vfb of − 1.01 V for HfO2−x films with an oxygen gas fraction of 5% during sputtering. Additionally, the Vfb of the HfO2−x/native SiO2−y stack could be controlled from − 1.01 to − 0.56 V by changing the deposition conditions of the HfO2−x film with the native SiO2−y interlayer. The findings of this study can be useful to fabricate charge-accumulating layers for backside-illuminated image sensor devices.
PubDate: 2018-02-20
DOI: 10.1007/s00339-018-1659-5
Issue No: Vol. 124, No. 3 (2018)

• Enhanced photoluminescence and thermal stability of divalent ions (Zn 2+ ,
Mg 2+ ) assisted CaTiO 3 :Eu 3+ perovskite phosphors for lighting
applications
• Authors: Dhananjay Kumar Singh; J. Manam
Abstract: Current study proposes the improved red emission of Zn2+ and Mg2+ ions incorporated CaTiO3:Eu3+ phosphors synthesized via the well-known solid-state reaction method. Under the 397 nm UV excitation, the Zn2+- and Mg2+-incorporated CaTiO3:0.15Eu3+ phosphor having orthorhombic structure with space group Pbnm exhibited an intense red emission at 619 nm. This can be credited to the hypersensitive 5D0 → 7F2 transition of Eu3+ ions, which is also indicative of the fact that the Eu3+ ions populated the non-inversion symmetry sites in the CaTiO3 lattices. The optimized composition CaTiO3:0.15Eu3+, 0.20Zn2+ and CaTiO3:0.15Eu3+, 0.10Mg2+ phosphors, pronounces in a magnificent enhancement of PL intensity by 5.5 and 2.5 times, respectively, as compared to CaTiO3:0.15 Eu3+ phosphor. From the temperature-dependent emission spectra, ∆Ea were enunciated to be 0.101 and 0.086 eV for CaTiO3:0.15Eu3+, 0.20Zn2+ and CaTiO3:0.15Eu3+, 0.10Mg2+ phosphors, respectively, for thermal quenching. In addition, it can be better understood as related to the adequate thermal stability of 60% even at 450 and 420 K, respectively. Furthermore, the Judd–Ofelt theory was used to study the radiative intensity parameters of Eu3+ ions in the CaTiO3 lattices. The experimental results incited the bright prospects of synthesized ceramics as a promising candidate for lighting applications.
PubDate: 2018-02-20
DOI: 10.1007/s00339-018-1665-7
Issue No: Vol. 124, No. 3 (2018)

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