Growth and Fabrication of GaAs Thin-Film Solar Cells on a Si Substrate via Hetero Epitaxial Lift-Off

We demonstrate, for the first time, GaAs thin film solar cells epitaxially grown on a Si substrate using a metal wafer bonding and epitaxial lift-off process. A relatively thin 2.1 μm GaAs buffer layer was first grown on Si as a virtual substrate, and a threading dislocation density of 1.8 × 107 cm−2 was achieved via two In0.1Ga0.9As strained insertion layers and 6× thermal cycle annealing. An inverted p-on-n GaAs solar cell structure grown on the GaAs/Si virtual substrate showed homogenous photoluminescence peak intensities throughout the 2″ wafer. We show a 10.6% efficient GaAs thin film solar cell without anti-reflection coatings and compare it to nominally identical upright structure solar cells grown on GaAs and Si. This work paves the way for large-scale and low-cost wafer-bonded III-V multi-junction solar cells.

Synthesis of calcium monosilicide nanowires by reactive deposition technique

The CaSi nanowires were synthesized on Si substrate by reactive deposition technique. A great amount of Ca vapor reacted with surface of cleaned Si substrate, and CaSi nanowires was grown on the as-synthesized CaSi film. The diameter of nanowires could achieve with a minimum value about 25 nm. The CaSi nanowire was self-orient along the <001> direction. We can control the length of nanowires by experimental parameter settings, such as quantity of Ca source, duration time and temperature. The formation mechanism of Ca-silicides on Si substrate was discussed in detail. Raman spectroscopy shows that the nanosized character for CaSi phase was confirmed. Meanwhile, the Ca-silicides layer showed a strong absorption in the ultraviolet (UV) region of the solar spectrum, indicating their potential applications.

Enhanced Mechanical and Tribological Capabilities of a Silicon Aluminum Alloy with an Electroplated Ni–Co–P/Si3N4 Composite Coating

Ni–Co–P/Si3N4 composite coatings were fabricated over an aluminum–silicon (Al–Si) substrate using a pulse-current electroplating process, in which the rapid deposition of an intermediate nickel–cobalt layer was used to improve coating adhesion. The microstructure, mechanical, and tribological behaviors of the electroplated Ni–Co–P/Si3N4 composite coating were characterized and evaluated. The results revealed that the electroplated Ni–Co–P/Si3N4 composite coating primarily consisted of highly crystalline Ni–Co sosoloid and P, and a volumetric concentration of 7.65% Si3N4. The electroplated Ni–Co–P/Si3N4 composite coating exhibited hardness values almost two times higher than the uncoated Al–Si substrate, which was comparable to hard chrome coatings. Under lubricated and dry sliding conditions, the electroplated Ni–Co–P/Si3N4 composite coating showed excellent anti-wear performance. Whether dry or lubricated with PAO and engine oil, the composite coating showed minimum abrasive wear compared to the severe adhesive wear and abrasive wear observed in the Al–Si substrate.

Erbium upconversion luminescence from sol–gel derived multilayer porous inorganic perovskite film

Erbium-doped barium titanate (BaTiO3:Er) xerogel film with a thickness of about 500 nm was formed on the porous strontium titanate (SrTiO[Formula: see text] xerogel film on Si substrate after annealing at 800[Formula: see text]C or 900[Formula: see text]C. The elaborated structures show room temperature upconversion luminescence under 980 nm excitation with the photoluminescence (PL) bands at 523, 546, 658, 800 and 830 nm corresponding to 2H[Formula: see text]4I[Formula: see text], 4S[Formula: see text]I[Formula: see text], 4F[Formula: see text]I[Formula: see text] and 4I[Formula: see text]4I[Formula: see text] transitions of trivalent erbium. Raman and X-ray diffraction (XRD) analysis of BaTiO3:Er\porous SrTiO3\Si structure showed the presence of perovskite phases. Its excellent up-conversion optical performance will greatly broaden its applications in perovskite solar cells and high-end anti-counterfeiting technologies.

Application of Bayesian Super-Resolution to Spectroscopic Data for Precise Characterization of Spectral Peak Shape

The number of data points of digitally recorded spectra have been limited by the number of multichannel detectors employed, which sometimes impedes the precise characterization of spectral peak shape. Here we describe a methodology to increase the number of data points as well as the signal-to-noise (S/N) ratio by applying Bayesian super-resolution in the analysis of spectroscopic data. In our present method, first, the hyperparameters for the Bayesian super-resolution are determined by a virtual experiment imitating actual experimental data, and the precision of the super-resolution reconstruction is confirmed by the calculation of errors from the ideal values. For validation of the super-resolution reconstruction of spectroscopic data, we applied this method to the analysis of Raman spectra. From 200 Raman spectra of a reference Si substrate with a data interval of about 0.8 cm−1, super-resolution reconstruction with a data interval of 0.01 cm−1 was successfully achieved with the promised precision. From the super-resolution spectrum, the Raman scattering peak of the reference Si substrate was estimated as 520.55 (+0.12, −0.09) cm−1, which is comparable to the precisely determined value reported in previous works. The present methodology can be applied to various kinds of spectroscopic analysis, leading to increased precision in the analysis of spectroscopic data and the ability to detect slight differences in spectral peak positions and shapes.

Сегнетоэлектрические свойства гетероструктуры Sr-=SUB=-0.5-=/SUB=-Ba-=SUB=-0.5-=/SUB=-Nb-=SUB=-2-=/SUB=-O-=SUB=-6-=/SUB=-/Ba-=SUB=-0.2-=/SUB=-Sr-=SUB=-0.8-=/SUB=-TiO-=SUB=-3-=/SUB=-/Si(001)

The properties of c-oriented thin films Sr0.5Ba0.5Nb2O6 grown on a Si(001) (p-type) substrate with a pre-deposited Ba0.2Sr0.8TiO3 layer were studied using scanning probe microscopy and dielectric spectroscopy. It is established that the films Sr0.5Ba0.5Nb2O6 are characterized by low surface roughness (less than 6 nm), average crystallite size 93 nm. It is shown that there is spontaneous polarization in the film directed from its surface to the substrate, which caused the manifestation of the field effect for the case of the Si substrate with p-type conductivity without external field effect. Differences in the magnitude of the surface potential signal for regions polarized by an external electric field of different polarities (+10 and −10 V), as well as in their relaxation to the initial state, are revealed. The reasons for the established patterns are discussed.

Theoretical aspects of direct conversion of radio-chemical energy in electric by radiation-stimulated SiC*/Si heterostructure

The authors consider their own CVD technology for the SiC growing on a Si substrate in order to create a beta converter. Since the beta converter contains a heavy C-14 atom, the finished beta converter works as an ”inner sun”, and the structure has specific mark * in the name: SiC*/Si. Authors focus on the problems of the theoretical description of: 1) the growth of the SiC*/Si film (with C-14 atoms inside) and the position of the p-n junction in the doping process; 2) method of a placement radioisotopes into a semiconductor material; 3) physical properties of radioisotopes; 4) defects formation; 5) generation of secondary electrons in the region of the p-n junction.

Graphene Growth Directly on SiO2/Si by Hot Filament Chemical Vapor Deposition

We report the first direct synthesis of graphene on SiO2/Si by hot-filament chemical vapor deposition. Graphene deposition was conducted at low pressures (35 Torr) with a mixture of methane/hydrogen and a substrate temperature of 970 °C followed by spontaneous cooling to room temperature. A thin copper-strip was deposited in the middle of the SiO2/Si substrate as catalytic material. Raman spectroscopy mapping and atomic force microscopy measurements indicate the growth of few-layers of graphene over the entire SiO2/Si substrate, far beyond the thin copper-strip, while X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy showed negligible amounts of copper next to the initially deposited strip. The scale of the graphene nanocrystal was estimated by Raman spectroscopy and scanning electron microscopy.