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Journal Cover physica status solidi (c)
  [SJR: 0.392]   [H-I: 39]   [1 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1862-6351 - ISSN (Online) 1610-1642
   Published by John Wiley and Sons Homepage  [1592 journals]
  • Low-k Spacers for 22 nm FDSOI Technology
    • Authors: Fabian Koehler; Bianca Antonioli, Dina H. Triyoso, Han Tao, Klaus Hempel
      Abstract: The Fully Depleted Silicon-on-Isolator (FDSOI) technology uses gate-fist High-k metal gate transistors fabricated on ultra-thin (< 7 nm) Silicon-on-Isolator. This SOI forms a fully depleted (FD) transistor channel constraining electrons. Low-k spacers reduce the parasitic capacitance. The FDSOI technology allows body biasing: The transistor Vt can be tuned under software control, which offers innovative solutions to designers for balancing between transistor performance and power efficiency.
      PubDate: 2017-12-14T07:28:45.627051-05:
      DOI: 10.1002/pssc.201770015
  • Proceedings of the 2017 E-MRS Spring Meeting Symposium P Silicon & Silicon
           Nanostructures: From Recent Fundamental Research to Novel Applications
    • PubDate: 2017-12-14T07:28:44.144911-05:
      DOI: 10.1002/pssc.201720016
  • Issue Information
    • PubDate: 2017-12-14T07:28:41.882539-05:
      DOI: 10.1002/pssc.201770115
  • Proceedings of the 2017 E-MRS Spring Meeting Symposium S ALTECH 2017 –
           Analytical techniques for precise characterization of nanomaterials
    • PubDate: 2017-12-14T07:28:41.556704-05:
      DOI: 10.1002/pssc.201720017
  • Tuning the Work Function of Si(100) Surface by Halogen Absorption: A DFT
    • Authors: Matteo Bertocchi; Michele Amato, Ivan Marri, Stefano Ossicini
      Abstract: First-principles calculations of work function tuning induced by different chemical terminations on Si(100) surface are presented and discussed. We find that the presence of halogen atoms (I, Br, Cl, and F) leads to an increase of the work function if compared to the fully hydrogenated surface. This is a quite general effect and is directly linked to the chemisorbed atoms electronegativity as well as to the charge redistribution at the interface. All these results are examined with respect to previous theoretical works and experimental data obtained for the (100) as well as other Si surface orientations. Based on this analysis, we argue that the changes in the electronic properties caused by variations of the interfacial chemistry strongly depend on the chemisorbed species and much less on the surface crystal orientation.A Si(100) surface supercell passivated by H and F atoms. Light blue spheres represent Si atoms, grey spheres H atoms and green spheres F atoms.
      PubDate: 2017-12-12T08:35:37.384296-05:
      DOI: 10.1002/pssc.201700193
  • Ellipsometric and X-Ray Spectrometric Investigation of Fibrinogen Protein
    • Authors: Benjamin Kalas; Beatrix Pollakowski, Andreas Nutsch, Cornelia Streeck, Judit Nador, Miklós Fried, Burkhard Beckhoff, Péter Petrik
      Abstract: Bovine fibrinogen monolayers on thin gold films and glassy carbon substrate were investigated using grazing incidence X-ray fluorescence (GIXRF) and spectroscopic ellipsometry (SE). The aim was to determine the amount of protein and to develop models and references for the SE measurement. Both methods were capable of measuring protein amount in the range of μg cm−2 with a sensitivity below 10%, which suggests the use of both techniques as complementary, combined methods. To do it with a high confidence, the lateral uniformity and the stability of the layers during transportation has to be investigated in more detail in the future.Spectroscopic ellipsometry (SE) and X-ray fluorescence (XRF) are used to measure protein monolayers on gold and amorphous carbon substrates. The amount of protein on the surface is quantified in terms of mass per unit area using de Feijter's method and a reference-free approach for SE and XRF, respectively. A good agreement is found, pointing out the importance of the lateral homogeneity and temporal stability.
      PubDate: 2017-12-06T14:23:18.973036-05:
      DOI: 10.1002/pssc.201700210
  • The Nitrogen Acceptor in 2H-Polytype Synthetic MoS2: Frequency and
           Temperature Dependent ESR Analysis
    • Authors: Ben Schoenaers; Andre Stesmans, Valery V. Afanas'ev
      Abstract: In extending on recent electron spin resonance (ESR) work which has revealed the N acceptor (N substituting for S site) in 2H-polytype bulk synthetic MoS2, the dopant is extensively analyzed in terms of its frequency, temperature (T), and magnetic field B angular dependent ESR spectral characteristics. For B∥c-axis, the multi-frequency analysis confirms the ESR spectrum as being composed of a 14N hyperfine (hf) triplet with hf splitting constant A∥ = 14.7 ± 0.2 G (B∥c-axis) and making up ≈74% of the total spectrum intensity, superimposed on a central line centered at about equal g-value [g∥ = 2.032(2)]. The presence of the latter signal, points to some non-uniformity in dopant distribution, that is, clustering, with about ≈26% of the total N response not originating from N incorporated in the preferred “isolated” dopant configuration. Angular dependent measurements reveal distinct anisotropy of the hf matrix, whereas ESR probing over a wide T-range exposes drastic signal broadening with increasing T above ≈150 K. Detailed study of the N acceptor signal intensity versus T at Q-band reveals an activation energy Ea = 50 ± 10 meV, herewith consolidating the value reported initially. Besides unveiling the S-site substitutional N impurity as an appropriate p-type dopant for MoS2, the total of the ESR work establishes a basic frame of the N acceptor ESR characteristics, giving way for further in-depth theoretical perusal.In extending on the recent electron spin resonance identification of the N acceptor in synthetic 2H-MoS2 (N substituting for S), the N signal has been extensively examined in terms of its frequency, temperature, and field angular dependent spectral characteristics. A detailed study of the N acceptor signal intensity versus temperature reveals an activation energy Ea ≈ 50 meV, exposing N as an appropriate p-type dopant for MoS2.
      PubDate: 2017-12-01T08:25:25.132376-05:
      DOI: 10.1002/pssc.201700211
  • Use of Rayleigh-Rice Theory for Analysis of Ellipsometry Data on Rough
           CIGS Films
    • Authors: Søren A. Jensen; Dana Maria Rosu, Andreas Hertwig, Poul-Erik Hansen
      Abstract: Ellipsometry is a useful tool for studying the optical properties of thin films such as photovoltaic devices. We employ Müller matrix ellipsometry to study the thin film photovoltaic material copper indium gallium selenide Cu(In,Ga)Se2 (CIGS), a commercially relevant material with high energy conversion efficiency. Confocal microscopy reveals an rms roughness of 68 nm, which greatly affects the ellipsometry data. Rayleigh-Rice theory is employed to account for the optical properties of the surface roughness in the ellipsometry experiment, and a library search method is used to compare Müller parameters calculated for various CIGS compositions, to the measured data. The Müller parameters calculated with the Rayleigh-Rice model are found to correspond well with the measured data, and a surface roughness of 37 nm and a correlation length of 125 nm are extracted.Ellipsometric measurements of photovoltaic CIGS thin films with significant surface roughness are interpreted using the analytical Rayleigh-Rice model. Roughness parameters are extracted and compared to reference measurements performed with confocal microscopy and AFM. This presents an alternative to commonly used effective-medium calculations for the analysis of ellipsometry data from rough surfaces.
      PubDate: 2017-11-24T11:01:38.697651-05:
      DOI: 10.1002/pssc.201700217
  • Effect of Cooling Rate on Dopant Spatial Localization and Phase
           Transformation in Cu-Doped Y-Stabilized ZrO2 Nanopowders
    • Authors: Nadiia Korsunska; Mykola Baran, Igor Vorona, Valentyna Nosenko, Serhiy Lavoryk, Yuliya Polishchuk, Vasyl Kladko, Xavier Portier, Larysa Khomenkova
      Abstract: The effect of calcination temperature (TC = 500–1000 °C) and cooling rate on the dopant distribution in Cu-doped Y-stabilized ZrO2 nanopowders is studied. The powders are produced by co-precipitation technique and investigated by attenuated total reflection, UV-vis diffuse reflectance, electron paramagnetic resonance, and transmission electron microscopy methods. The cooling rate is found to affect the amount of Cu substances on grain surface, the powders subjected to fast cooling (quenching) showed higher amount of Cu-related complexes on the grains’ surface than their counterparts cooled with furnace after calcination. It is observed that Cu impurities diffuse inside ZrO2 grains from Cu-related surface substances when TC  800 °C, outward migration of Cu dopants takes place. Simultaneously, the intensity of 275-nm absorption band decreases, the monoclinic ZrO2 phase forms and its contribution rises with TC. It is proposed that monoclinic phase formation is caused by the replacement of Cu atoms from lattice sites to interstitials leading to an appearance of the channels for Y out-diffusion via cation vacancies and destabilization of ZrO2 tetragonal phase.Copper spatial localization in (Cu,Y)-ZrO2 powders is controlled by the cooling rate after high-temperature annealing. Quenching results in Cu content decrease inside Y-ZrO2 grains that is reflected by the weakening of narrow sharp EPR lines related to substitutional Cu and by the enhancing of broad EPR signal and diffuse reflectance band at 600-800 nm band originated from Cu-contained surface substances.
      PubDate: 2017-11-24T01:06:20.612882-05:
      DOI: 10.1002/pssc.201700183
  • Spatially-Resolved Spectroscopic Characterization of Reflective and
           Transparent Materials at a Micro-Meter Scale Using Coherence Scanning
    • Authors: Rémy Claveau; Paul C. Montgomery, Manuel Flury
      Abstract: The development of new technologies and innovative products today is often accompanied by the emergence of new micro and nanomaterials. Due to their wider use in many applications, performing accurate characterization of these materials is becoming essential. The high performance of coherence scanning interferometry for materials characterization in terms of topographic, roughness and thickness measurements as well as for tomographic analysis of transparent layers has already been well demonstrated. However, demands regarding the spectral characterization of these materials requires new operation modes using the combination of spectral measurements with high resolution imaging. In this work we present a technique for local spectral measurements by careful processing of the entire interferometric signal over the scanned depth at each pixel in the image, so providing spatially resolved measurements in both the lateral and axial directions. Being a far-field technique, and because the sample is illuminated with a white light source, spectral information is obtained over large areas (150 × 150 μm2) at the same time and for all the wavelengths. Spectroscopic mapping of a sample consisting of four different materials (Si, Al, Ag, Ti) and depth-resolved measurements performed through a thin layer of PDMS are reported. Spectral measurements are made over an area of about 1–2 μm2, with an axial resolution of 1 μm, these features being dependent on the optical parameters of the system.The characterization method is based on the processing and the spectral analysis of interferometric signals. It can be used for depth-resolved spectral measurements or for performing surface spectroscopic mapping. Then it enables the identification of four different materials through their spectral response.
      PubDate: 2017-11-24T01:05:54.178698-05:
      DOI: 10.1002/pssc.201700157
  • Construction of the Energy Band Diagram of Hydrogen Terminated Diamond and
           Silicon Nanowires
    • Authors: Susanna Challinger; Iain Baikie, A. Glen Birdwell, Steffen Strehle
      Abstract: We demonstrate the use of a combined ambient pressure and UHV photoemission system for absolute work function characterization. We describe measurements of the valence band position of Hydrogen Terminated Synthetic Diamond (HTSD) under different pressures. The diamond exhibits a nanoscale surface conductivity with a 2D hole gas of ≈10 nm depth. The same system also allows contact potential difference Kelvin probe measurements for determination of relative Fermi level position from 1 to 1.1 × 10−11 Bar. Combined with UV-Surface Photovoltage determination of the band gap, this allows a complete reconstruction of the surface energy band diagram of this material. The valence band edge was found to be 4.9 eV under ambient conditions and 4.4 eV under UHV, relative to the vacuum level. The ambient pressure photoemission technique was also used to reconstruct the energy band diagram of bottom-up grown silicon nanowires. They had a valence band maximum at 5.04 ± 0.05 eV. Both the HTSD and silicon nanowires had high photoemission yield characteristics which suggests that these materials could be used as an electron source. This illustrates the suitability of photoemission and Kelvin probe techniques for investigating the macroscopic work function characteristics of surfaces with nanostructures and nanoscale surface conductivity.We demonstrate a novel UHV to ambient pressure, photoemission and Kelvin probe system, for energy level characterisation of hydrogen terminated diamond and silicon nanowire surfaces. We compare photoemission measurements of hydrogen terminated diamond under different conditions, illustrating the suitability of these techniques for investigating the macroscopic work function characteristics of surfaces.
      PubDate: 2017-11-23T04:41:33.535734-05:
      DOI: 10.1002/pssc.201700152
  • Strain and Compositional Analysis of (Si)Ge Fin Structures Using High
           Resolution X-Ray Diffraction
    • Authors: Andreas Schulze; Roger Loo, Liesbeth Witters, Hans Mertens, Andrzej Gawlik, Naoto Horiguchi, Nadine Collaert, Matthew Wormington, Paul Ryan, Wilfried Vandervorst, Matty Caymax
      Abstract: The performance of heterogeneous 3D transistor structures critically depends on the composition and strain state of the buffer, channel, and source/drain regions. In this paper we discuss the value of in-line high resolution X-ray diffraction (HRXRD) measurements based on three representative examples. First, we analyzed the strain state of etched Ge fins in the two in-plane directions. We could verify a loss in channel strain after growth of a Si cap which we attribute to Ge reflow. Secondly, we studied the composition and strain state of relaxed SiGe fins selectively grown in an STI matrix where we found an anisotropic in-plane strain state with significantly reduced relaxation in the direction along the fin. Finally, we used HRXRD for the analysis of complex multilayer fin structures which are relevant for horizontal nanowire FETs that are candidates to replace FinFETs below the 7 nm technology node. With this example we could demonstrate that HRXRD is capable of providing insight into fin stress created by interlayer dielectrics (ILD0).Asymmetric (113) reciprocal space map (RSM) acquired on Si/SiGe multilayer fin structures with the scattering plane perpendicular to the fins.
      PubDate: 2017-11-22T10:56:55.129447-05:
      DOI: 10.1002/pssc.201700156
  • Scan-Free Grazing Emission XRF Measurements in the Laboratory Using a CCD
    • Authors: Veronika Szwedowski; Jonas Baumann, Ioanna Mantouvalou, Leona Bauer, Wolfgang Malzer, Birgit Kanngießer
      Abstract: The rapid development of new classes of nanomaterials calls for easy access methods in order to quantify properties essential for their functionality, e.g., interdiffusion of elements at interfaces, or elemental dopant, or depth profiles. Non-destructive methods, like X-ray fluorescence (XRF), are of special interest, for preserving materials and offering the possibility to incorporate the analysis in a production process. In-depth XRF methods for the characterization of nanomaterials are up until now limited to synchrotron radiation facilities. A novel scan-free grazing emission XRF (GEXRF) setup is presented utilizing conventional and low-cost hardware, acting as a transfer of a synchrotron method into the laboratory. A chromium target X-ray tube with a polycapillary lens is used as X-ray source and a conventional CCD as the 2D energy-dispersive detector. To confirm the feasibility of the described setup a nanometer-layered titanium-aluminium sample is measured. An energy-dispersive spectrum is obtained in single-photon-counting-mode from the CCD measurements and first GEXRF profiles generated. A semi-quantitative evaluation of this setup is implemented by comparing the measured results with simulations, allowing conclusions about the investigated samples’ elemental, compositional, and structural layer-by-layer characteristics.A novel scan-free grazing emission XRF (GEXRF) setup for laboratory use is presented utilizing conventional and low-cost hardware. This method allows the non-destructive investigation of interdiffusion of elements at interfaces, or elemental dopant, or depth profiles of nanomaterials. A semi-quantitative evaluation of this setup is implemented by comparing the measured results with simulations, allowing conclusions about the investigated samples’ elemental, compositional and structural layer-by-layer characteristics.
      PubDate: 2017-11-22T03:51:35.66711-05:0
      DOI: 10.1002/pssc.201700158
  • Nanoscale Mapping of Semi-Crystalline Polypropylene
    • Authors: Kerry J. Abrams; Quan Wan, Nicola A. Stehling, C. Jiao, Abdullah C. S Talari, Ihtesham Rehman, Cornelia Rodenburg
      Abstract: We reveal nanoscale information of semi-crystalline polypropylene with the use of a new secondary electron hyperspectral imaging technique. The innovative combination of cryo-SEM and low voltage allows for the optimized imaging of these beam-sensitive materials. Through the collection of secondary electron hyperspectral imaging data, mapping of molecular order on the nano-scale in the scanning electron microscope (SEM) can be achieved.Nanoscale information of cross-sectional semicrystalline microporous polypropylene (MPP) has been obtained with a technique called Secondary electron hyperspectral imaging (SEHI) which allows the selection of specific secondary electron (SE) energy ranges via the setting of a mirror voltage (MV). The figures show the same area imaged with different SE energy ranges to isolate different constituent phases of polypropylene.
      PubDate: 2017-11-22T03:51:30.896319-05:
      DOI: 10.1002/pssc.201700153
  • Characterization of Nanometer-Sized Oxygen Precipitates in Highly B-Doped
           Czochralski Silicon
    • Authors: Dawid Kot; Gudrun Kissinger, Markus Andreas Schubert, Steffen Marschmeyer, Georg Schwalb, Andreas Sattler
      Abstract: We use a wide variety of analytical methods to characterize nanometer-sized oxygen precipitates in highly B-doped Czochralski (CZ) silicon. Due to the enhanced precipitation of oxygen in this type of wafer, the precipitate density reaches a value of 1 × 1013 cm−3 already after short annealing. On the one hand, this provides an excellent possibility for testing the detection limits of different methods and on the other hand the knowledge on oxygen precipitation in p+ material can be broadened. In order to study density, size, and morphology of oxygen precipitates, we exploit scanning transmission microscopy (STEM), reactive ion etching (RIE), and preferential etching. STEM is also used to determine size distribution and energy dispersive X-ray spectroscopy (EDX) and electron energy loss spectroscopy (EELS) are used to investigate the composition of oxygen precipitates. In annealed samples, oxygen precipitates, dislocation loops, and stacking faults are found. The dislocation loops disappear after long annealing in contrast to the stacking faults which are detected in all samples annealed at 1000 °C. It is found that the long anneal at 1000 °C leads to the formation of two size fractions of precipitates. This process is similar to Ostwald ripening. The precipitates are octahedral, consist of SiO2 and the B concentration is below the detection limit of the methods used here. The obtained results are in good agreement with the nucleation model of highly doped wafers proposed by Sueoka.In this work, we investigated density, size, size distribution, morphology, and composition of oxygen precipitates in highly B-doped Czochralski silicon wafers. It was found that the long anneal at 1000 °C leads to the formation of two size fractions of precipitates. This process is similar to Ostwald ripening. The precipitates are octahedral and consist of SiO2.
      PubDate: 2017-11-17T11:10:38.143856-05:
      DOI: 10.1002/pssc.201700161
  • Low-k Spacers for 22 nm FDSOI Technology
    • Authors: Fabian Koehler; Bianca Antonioli, Dina H. Triyoso, Han Tao, Klaus Hempel
      Abstract: As standard planar transistors have reached their scaling limit new sophisticated architectures have found their way into mass production. One option is the Fully Depleted Silicon-on-Isolator (FDSOI) technology, which combines performance efficiency with a cost effective, planar architecture. Approximately, 75% of the process steps in FDSOI can be leveraged from the established 28 nm bulk technology, while there are certain process modules that require the introduction of new processes, i.e., low-k spacer deposition and the epitaxial growth of SiGe gate channels and Si:B, SiGe:B source/drain regions. In this article, we want to focus on the deposition of the low-k spacer, which provides low gate-to-drain capacitances. The standard SiN spacer was replaced by a SiBCN spacer. Electrical results show a clear 10% increase in ring-oscillator frequency.The Fully Depleted Silicon-on-Isolator (FDSOI) technology uses gate-fist High-k (HK) metal gate transistors fabricated on ultra-thin Silicon-on-Isolator. This SOI forms a fully depleted (FD) transistor channel constraining electrons. Low-k (LK) spacers reduce the unintentional parasitic capacitances significantly and thus increase the ring-oscillator frequency by 10%. I addition, the low-k spacers define the placement of the epitaxial grown source-/drain (SD) contacts.
      PubDate: 2017-11-17T11:10:29.858952-05:
      DOI: 10.1002/pssc.201700196
  • Carrier Multiplication in Silicon Nanocrystals: Theoretical Methodologies
           and Role of the Passivation
    • Authors: Ivan Marri; Marco Govoni, Stefano Ossicini
      Abstract: Carrier multiplication is a non-radiative recombination mechanism that leads to the generation of two or more electron–hole pairs after absorption of a single photon. By reducing the occurrence of dissipative effects, this process can be exploited to increase solar cell performance. In this work, we introduce two different theoretical fully ab initio tools that can be adopted to study carrier multiplication in nanocrystals. The tools are described in detail and compared. Subsequently, we calculate carrier multiplication lifetimes in H- and OH-terminated silicon nanocrystals, pointed out the role played by the passivation on the carrier multiplication processes.The Si35(OH)36 is depicted in the left part of the figure. On the right, we schematize the carrier multiplication decay process ignited by the relaxation of a hole.
      PubDate: 2017-11-15T12:15:50.869359-05:
      DOI: 10.1002/pssc.201700198
  • Determination of Shape and Sphericity of Silicon Quantum Dots Imaged by
    • Authors: Daniel Hiller; Sebastian Gutsch, Julian López-Vidrier, Margit Zacharias, Sònia Estradé, Francesca Peiró, Irving Cruz-Matías, Dolors Ayala
      Abstract: The shape of size-controlled silicon nanocrystals (Si NCs) embedded in SiO2 is investigated by tomographic energy-filtered transmission electron microscopy (EFTEM). The sphericity of the quantum dots is determined by computational analyses. In contrast to other fabrication methods, we demonstrate that the NCs in superlattices are non-agglomerated, individual clusters with slightly oblate spheroidal shape. This allows for low surface-to-volume ratios and thereby low non-radiative defect densities as required by optoelectronic or sensing applications. A near-spherical shape is also a prerequisite for the direct comparison of Si quantum dots (QDs) with theoretical simulations.Voxel model of the tomographic EFTEM-reconstruction used in this study to analyze the shape of size-controlled Si NCs.
      PubDate: 2017-11-06T04:39:45.692802-05:
      DOI: 10.1002/pssc.201700216
  • Optical Modeling of Ultrathin Silicon Solar Cells with PC1D
    • Authors: Luigi Abenante
      Abstract: We show that the optical diffusion model embedded in the numerical simulation program PC1D systematically underestimates light-generated currents in thin textured Si solar cells. The demonstration exploits the exact analytical solution to minority-carrier transport in uniformly doped regions and the fact that, at the first pass of internal light, the average optical propagation angle, θ, with respect to the device normal is determined by surface texture. We provide a simple correction procedure to remove the aforementioned systematical error. One can so reliably model with PC1D the optical performance of textured thin devices at standard Lambertian regimen (θ = 60° at all wavelengths, λ) that starts at either the first or the second pass of trapped light. We exploit such a possibility to scrutinize with PC1D a reported non-standard Lambertian optical model, where θ varies with λ.An embedded routine causes the simulation program PC1D to underestimate lightgenerated currents in thin textured silicon solar cells. Such routine is necessary when standard Lambertian optics starts at the second or third optical pass across a cell. A correction procedure is provided and applied to check a reported nonstandard Lambertian model.
      PubDate: 2017-11-02T08:40:39.687515-05:
      DOI: 10.1002/pssc.201700155
  • An innovative ion sensitive device based on side-contacted field effect
    • Authors: Ehsan Mohammadi; Negin Manavizadeh
      Abstract: In this paper, side-contacted field effect diode as an ion sensitive device is proposed to take advantages of field effect diodes family in sensing ionic species in solutions. To analyze the behavior of ion sensitive side-contacted field effect diode, an accurate model has been developed in a simulation environment tool to mimic the characteristics of the solution and the results compared with the literature. While dual gate ion sensitive FETs have been introduced to beat the Nernst limit, results show that dual gate ion sensitive side-contacted field effect diodes can provide better performance. Effects of various parameters such as silicon body thickness and doping concentration have been studied. In contrast of ISFETs, the proposed device offers more sensitivity at the thicker silicon body. Results indicate that dual gate ion sensitive side-contacted field effect diodes can be regarded as an interesting candidate for bio-sensing applications.Side-contacted field effect diode introduced as a promising candidate for ion-sensing application. Simulation results reveal that two different path forming in the channel: An n-MOS and a p-MOS. This happens due to special doping profile which in contrast of traditional ISFETs, offers more sensitivity at the thicker silicon body.
      PubDate: 2017-11-02T03:14:07.706048-05:
      DOI: 10.1002/pssc.201700202
  • Effect of Interstitials Embedded in Pre-Patterned Si Substrate on Location
           of Ge Nanoislands
    • Authors: Pavel L. Novikov; Timur Atovullaev, Zhanna V. Smagina, Anatoly V. Dvurechenskii, Kirill V. Pavskii
      Abstract: Large-area periodical pattern on Si(100) was fabricated using combination of nanoimprint lithography and ion irradiation through mask. Ordered structures with grooves and ridges were prepared by the selective etching of regions amorphized by ion irradiation. Laterally ordered chains of Ge nanoislands were grown by molecular beam epitaxy of Ge on the pre-patterned Si substrates. It was shown, that the location of subsequently grown Ge nanoislands depends upon the sidewall inclination in grooves. The effect is ascribed to strain induced by Ge interstitials under the groove's bottom. Our proposal was confirmed by molecular dynamics calculations that allowed the determination of strain in grooves as dependent on the groove's shape.Laterally ordered chains of Ge nanoislands were grown by molecular beam epitaxy of Ge on the pre-patterned Si substrates. The prepatterning procedure includes ion irradiation and allows control over location of consequently grown Ge nanoislands. The MD calculations of strain formed by irradiation induced interstitials demonstrate a qualitative agreement with the experimental results.
      PubDate: 2017-11-02T03:13:58.171006-05:
      DOI: 10.1002/pssc.201700200
  • Local Formation of InAs Nanocrystals in Si by Masked Ion Implantation and
           Flash Lamp Annealing
    • Authors: Lars Rebohle; René Wutzler, Slawomir Prucnal, René Hübner, Yordan M. Georgiev, Artur Erbe, Roman Böttger, Markus Glaser, Alois Lugstein, Manfred Helm, Wolfgang Skorupa
      Abstract: The integration of high-mobility III–V compound semiconductors emerges as a promising route for Si device technologies to overcome the limits of further down-scaling. In this work, we investigate the possibilities to form InAs nanocrystals in a thin Si layer at laterally defined positions with the help of masked ion beam implantation and flash lamp annealing. In detail, a cladding layer was deposited on a silicon-on-insulator (SOI) wafer and patterned by electron beam lithography in order to serve as an implantation mask. The wafer was subsequently implanted with As and In, followed by flash lamp annealing leading to the formation of InAs nanoparticles in the implanted areas. The structures were investigated by Raman spectroscopy, scanning, and transmission electron microscopy as well as energy-dispersive X-ray spectroscopy. Depending on the size of the implantation window, several, one or no nanoparticle is formed. Finally, the perspectives for using this technique for the local modification of Si nanowires are discussed.InAs nanocrystals are formed in a thin Si device layer at laterally defined positions by electron beam lithography, masked ion beam implantation and flash lamp annealing. Depending on the size of the implantation window, several, one or no nanoparticle is formed. Finally, the pro and cons of this technique for the local modification of Si nanowires are discussed.
      PubDate: 2017-10-13T07:10:25.123555-05:
      DOI: 10.1002/pssc.201700188
  • Characterization of CuIn0.7Ga0.3Se2 Thin Films Deposited by Single Stage
           Thermal Evaporation Process
    • Authors: Hakan Karaagac; Elif Peksu, Hamed Behzad, Sare Akgoz, Mehmet Parlak
      Abstract: Single phase CuIn0.7Ga0.3Se2 (CIGS) thin films are successfully deposited on glass substrates via a single stage thermal evaporation from a stoichiometric powder of CIGS. X-ray photoelectron spectroscopy measurements reveal the existence of Cu- and Ga-rich surface of the as-grown CIGS thin films. The post-growth annealing process lead to migration of the metallic atoms from the surface region into the bulk during the crystallization process, which subsequently causes a significant reduction in the reflection and a change in the mechanism of conduction. From the photoconductivity measurements it was deduced that the deposited CIGS films demonstrated a drastic decrease in resistivity under different illumination intensities. The post-growth annealing effect on the morphology and structure of CIGS thin films is investigated by means of the atomic force microscopy and X-ray diffraction measurements, respectively. Results show that there is a significant change in surface roughness as well as in degree of crystallinity of the films following the annealing process at different temperatures.Recently, Cu (In, Ga)Se2 thin films have attracted a great attention due to their superior properties as absorber layers in thin film based solar cells. In general, complex multi-stage processes based methods are used for the fabrication of these films. This study, however, presents the achievement of a single phase CuIn0.7Ga0.3Se2 thin films via a simple single stage thermal evaporation of a stoichiometric powder.
      PubDate: 2017-10-09T03:02:18.899798-05:
      DOI: 10.1002/pssc.201700145
  • Study of Electron Traps Associated With Oxygen Superlattices in n-Type
    • Authors: Eddy Simoen; Suseendran Jayachandran, Annelies Delabie, Matty Caymax, Marc Heyns
      Abstract: In this paper, the deep levels found by Deep-Level Transient Spectroscopy in Si-O superlattices (SLs) on n-type silicon are reported. Samples have been grown with one, two or five silicon-oxygen layers, separated by 3 nm of silicon. A Cr Schottky barrier (SB) is thermally evaporated on top of the SL. Similar as for p-type silicon, no deep levels have been found for a bias pulse in depletion, while a broad distribution of electron traps shows up when pulsing into forward bias. At the same time, these bands are absent in a zero SL reference sample. Similar as for the p-type results, the trap filling of the electron states exhibits a logarithmic capture. The possible origin of this slow filling will be discussed.The deep levels found by Deep-Level Transient Spectroscopy in Si-O superlattices (SLs) on n-type silicon are reported. A broad distribution of electron traps shows up when pulsing into forward bias. The trap filling of the electron states exhibits a logarithmic capture, indicating an extended-defect origin.
      PubDate: 2017-09-28T01:35:32.104989-05:
      DOI: 10.1002/pssc.201700136
  • Photoluminescence from Ordered Ge/Si Quantum Dot Groups Grown on the
           Strain-Patterned Substrates
    • Authors: Anatoly Dvurechenskii; Aigul Zinovieva, Vladimir Zinovyev, Alexey Nenashev, Zhanna Smagina, Sergey Teys, Aleksandr Shklyaev, Simon Erenburg, Svetlana Trubina, Olga Borodavchenko, Vadim Zhivulko, Aleksandr Mudryi
      Abstract: The photoluminescence (PL) properties of combined Ge/Si structures representing a combination of large (200–250 nm) SiGe disk-like quantum dots (QDs) and the groups of smaller (40–50 nm) laterally ordered QDs grown on the nanodisk surface are studied. The experimental results are analyzed basing on the calculations of energy spectra, electron and hole wave functions. It is found that the strain accumulation in multi-layered structure is the main factor providing the room temperature PL. The new type of QD structures that should provide the observation of enhanced PL from SiGe QDs at room temperature is proposed. The structures represent the stacked compact groups of laterally aligned QDs incorporated in Si at the distance 30–40 nm above the large nanodisks.The persistent room temperature photoluminescence of Ge/Si structures with ordered quantum dot (QD) groups grown on the strain-modulated Si substrates with embedded large (200–250 nm) SiGe disks is found (see figure). The strain accumulation is shown to be main factor providing the increasing binding energy of carriers localized in QD structures and an observation of the room temperature photoluminescence.
      PubDate: 2017-09-15T13:07:16.988867-05:
      DOI: 10.1002/pssc.201700187
  • Hydrophilic Luminescent Silicon Nanoparticles in Steric Colloidal
           Solutions: Their Size, Agglomeration, and Toxicity
    • Authors: Kateřina Herynková; Petra Šimáková, Ondřej Cibulka, Anna Fučíková, Marie Hubálek Kalbáčová
      Abstract: Luminescent silicon nanoparticles are promising for intracellular biological research as luminescent probe for in vitro and in vivo studies. We prepared nanoclusters of hydrophilic highly porous silicon having the size around 100 nm, composed of nanocrystals ∼2.5 nm in size, by electrochemical etching. Colloidal suspensions of the nanoparticles in steric organics (bovine serum albumin (BSA), glutamic acid, dextran, and glycine) were prepared to attempt to stabilize the nanoparticles and prevent their further agglomeration. The zeta potential differs from sample to sample – BSA and glycine solutions have zeta potential between −30 and −40 mV indicating good stability of nanoparticles in the solutions, while the zeta potentials of water (−24 mV), dextran (−10 mV), and glutamic acid (−14 mV) are showing that nanoparticles tend to agglomerate. Strong orange luminescence of nanoparticles is situated between 600 and 700 nm and remains stable in all used organic colloidal solutions. Performed study of in vitro toxicity revealed that sterically stabilized silicon nanoparticles are cytotoxic only at the highest used concentration (500 μg ml−1) of the silicon nanoparticles in water and BSA. Only in the case of glycine a significant decrease of the cell viability was observed already at a lower concentration of 250 μg ml−1 and is caused probably by glycine itself.The in vitro cytotoxicity of colloidal solutions of luminescent silicon nanoparticles wrapped in bovine serum albumin and glycine is studied and compared to the cytotoxicity of silicon nanoparticles in water solutions. The nanoparticles are cytotoxic only at highest used concentrations of 500 μm ml−1.
      PubDate: 2017-09-11T02:50:21.358788-05:
      DOI: 10.1002/pssc.201700195
  • Formation and Strain Analysis of Stacked Ge Quantum Dots With
           Strain-Compensating Si1−xCx Spacer
    • Authors: Yuhki Itoh; Tomoyuki Kawashima, Katsuyoshi Washio
      Abstract: To stack Ge quantum dots (QDs) in a multilayer structure without undesirable enlargement of the QDs, the effects of both Si1−xCx spacer on a strain compensation of the embedded QDs and a sub-monolayer (ML) carbon (C) mediation on a formation of the Volmer-Weber (VW)-mode Ge QDs on the Si1−xCx spacer were investigated. In a Si1−xCx/Ge/Si(100) structure, lattice rexation of the embedded QDs was kept about 80% at x = 0.015. This maintaining the state of high relaxation attributed to a tensile strain from the Si1−xCx layer grown on a surface of a Si substrate around the QDs. In addition, by utilizing an analysis of Kelvin probe force microscopy, it was revealed that the sub-ML C mediation of 0.25 ML and over is effective to form the VW-mode Ge QDs on the Si1−xCx spacer. This is because the promotion of subdivision effect for the formation of the QDs via C mediation was also effective on the Si1−xCx surface. At C = 0.25 and 0.5 ML, diameter and density of second QDs were about 22 nm and 1.5 × 1011 cm−2, respectively. These results pave the way to stack the VW-mode Ge QDs in the multilayer structure without enlargement of the QDs.In this work, a Si1-xCx layer was used as a strain-compensating layer to stack Ge quantum dots (QDs) in a multilayer structure without undesirable enlargement of the QDs. In-plane XRD (shown in figure) and Raman spectroscopy results revealed that the undesirable compressive strain of the embedded QDs was relaxed by introducing Si1-xCx layer.
      PubDate: 2017-09-11T02:07:28.231475-05:
      DOI: 10.1002/pssc.201700197
  • Influence of the Chemical Activity of Implanted Ions on the Structure of
           the Damaged Si Layer in SIMOX Substrates
    • Authors: Kirill Shcherbachev; Victor Mordkovich, Elena Skryleva, Dmitry Kiselev
      Abstract: High-resolution X-ray diffraction (HRXRD), X-ray reflectometry (XRR), X-ray photoelectron spectroscopy (XPS), and Atomic-force microscopy (AFM) were used to study the influence of the chemical activity of implanted ions (N+, O+, F+ or Ne+) on the structure of the damaged Si layer in SIMOX substrates. The implantation conditions were chosen so that the number of primary defects and the projected range were approximately the same for the implanted ions. HRXRD showed that the depth distribution of the residual damage depends on the chemical activity of the impurity. This may result from the quasi-chemical interaction between the radiation-induced point defects (VSi and Sii) and the impurity atoms. The shape of the density profiles and the thickness of the transition surface layer obtained from the XRR data are different for the implanted ions. The [100] faceted surface features of the samples prepared by SIMOX technology are preserved after implantation with the ions. AFM revealed a reduction of the lateral correlation length. The magnitude of this effect depends on the chemical activity of the implanted ions. Silicon oxidation at a depth of 10–15 nm is shown by XPS to change depending on the implanted ion.A significant difference in the form of the XRD curves is observed, although the number of the displaced atoms was the same. This means that the number of the residual radiation induced point defects differs from ion to ion. Thus, the chemical activity of the implanted ions influences the final composition of the defect ensemble in the damaged layer.
      PubDate: 2017-08-02T08:20:39.114083-05:
      DOI: 10.1002/pssc.201700137
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