Yuriy Kudriavtsev - Academia.edu (original) (raw)

Papers by Yuriy Kudriavtsev

Revista Mexicana De Fisica, 2017

In this work we study the atomic composition in SiGe:H films as a function of hydrogen dilution. ... more In this work we study the atomic composition in SiGe:H films as a function of hydrogen dilution. Silane and germane fluxes are kept constant while hydrogen flow is varying to achieve dilutions up to 80 times. Solid content of principle elements as well as contaminants are determined by SIMS. For low dilutions (from 9 to 30), germanium solid content strongly depends on hydrogen dilution since it varies from 0.485 to 0.675. Higher presence of hydrogen in the mixture does not change germanium content which remains close to the value of 0.69.

Japanese Journal of Applied Physics, Aug 1, 2000

In this study, a pn homojunction was intentionally fabricated in the Cu(InGa)Se2 (CIGS) layer by ... more In this study, a pn homojunction was intentionally fabricated in the Cu(InGa)Se2 (CIGS) layer by Zn doping. For Zn doping of the CIGS layer, Zn was evaporated after CIGS formation, and a potential improvement in cell performance was confirmed by this technique. Furthermore, Zn diffusion into the CIGS film was investigated by secondary ion mass spectroscopy (SIMS). A conductivity-type conversion from p-type to n-type was studied by the measurement of the cross-sectional electron beam-induced current (junction EBIC: JEBIC) and the spectral response of solar cells. A conversion efficiency of 11.5% has been achieved using the Zn-doped CIGS layer without a buffer layer and by the formation of a pn homojunction in the CIGS absorber.

Solid State Ionics, 2021

Abstract A comparative analysis of interaction of various borosilicate glasses with water vapor i... more Abstract A comparative analysis of interaction of various borosilicate glasses with water vapor is carried out in the work. The fundamental dependence of the observed processes on the concentration of alkali metal oxides as well as glass formers B2O3 and Al2O3 in glass is shown. The relative content of alkali oxides determines which processes dominates. The absence of alkali metal oxides leads to the fact that no hydrated or hydrogenated layers are formed on the surface of the glass. At a concentration of alkali metal oxides above ~15% by weight, hydration of the glass surface is observed as a result of the ion exchange reaction of water protons and alkali ions; the hydrated layer grows with time of hydration according to a parabolic law. However, at a concentration of alkali metal oxides below about 8% weight, the ion exchange reaction stops after formation of a 20 nm thick hydrated layer due to a sharp decrease in the “solubility” of alkalis in a thin water layer adsorbed on the surface due to an increase of pH factor, and due to a radical decrease concentration gradients for Na and H in the glass and in the solution. And then the formation of a hydrogenated layer with the formation of silicon hydroxides in the NaBSixOy molecular complexes is observed. The top surface hydrated layer acts as a source of protons for this reaction. The growth of the hydrogenated layer occurs with time according to a linear-parabolic law.

Applied Surface Science, 2018

Germanium crystals were implanted with low-energy and high-dose silicon ions. The implantation le... more Germanium crystals were implanted with low-energy and high-dose silicon ions. The implantation led to amorphization of a near-surface layer due to the formation of many adatoms and vacancies. Adatoms can be absorbed in germanium by the amorphous matrix faster than vacancies. The excess of vacancies and their ability to cluster resulted in formation of a porous structure beneath the surface. Pores of different sizes and depths were observed experimentally. A subsequent thermal annealing was carried out at 973 K in order to repair the damage due to the implantation. The annealing resulted, among other things, in oxidation of the pores. Visible white luminescence was observed for the as-implanted samples at the 325 nm excitation wavelength; the photoluminescence intensity increased after the annealing. The optical properties were attributed to the combined effects of different defects and the formation of germanium oxides with oxygen deficiencies.

2016 13th International Conference on Electrical Engineering, Computing Science and Automatic Control (CCE), 2016

In this work we study the high contrast distributed Bragg reflectors (DBRs) based on plasma depos... more In this work we study the high contrast distributed Bragg reflectors (DBRs) based on plasma deposited Si:H/SiC:H films. Optical constants of these materials were measured by means of spectral ellipsometry and used in theoretical calculations of spectral transmittance and reflectance. The stacks consisted of 13 layers of the films were designed to provide stop band center at λ= 835 (DBR1) and 565 nm (DBR2). High reflectance (>90%) for DBR1 and lower value of 70% for DBR2 was measured with bandwidth Δλ=260 nm. The properties of DBR1 are of promise as back reflector in PECVD PV solar cells because of his stop band characteristics and complete compatibility with solar cell fabrication. While DBR2 structure shows worse filter properties suggesting significant effect of light absorption in Si:H layers.

Journal of Alloys and Compounds, Nov 1, 2022

Materials, 2020

In this work, we present the study of the atomic composition in amorphous SiXGeY:HZ films deposit... more In this work, we present the study of the atomic composition in amorphous SiXGeY:HZ films deposited by radio frequency (RF—13.56 MHz) plasma discharge at low deposition temperature. A study and control of Si and Ge atoms termination using H-dilution in SiGe:H alloys deposited by RF plasma discharge was conducted and we made a comparison with low-frequency plasma discharge studies. Solid contents of the main elements and contaminants were determined by SIMS technique. It was found that for low dilution rates from RH = 9 to 30, the germanium content in the solid phase strongly depends on the hydrogen dilution and varies from Y = 0.49 to 0.68. On the other hand, with a higher presence of hydrogen in the mixture, the germanium content does not change and remains close to the value of Y = 0.69. The coefficient of Ge preferential incorporation depended on RH and varied from PGe = 0.8 to 4.3. Also, the termination of Si and Ge atoms with hydrogen was studied using FTIR spectroscopy. Prefer...

MRS Proceedings, 2008

We report the influence of surface treatment, annealing temperature and metal bilayer thickness o... more We report the influence of surface treatment, annealing temperature and metal bilayer thickness on the specific contact resistance (ρc) of Au/Ni ohmic contacts to p-GaN and p-AlGaN. Ohmic contact on p-GaN with a hole concentration of 6.5 x 1017 cm-3, shows the lowest ρc of ˜9.2 x 10-6 Ω cm2, when GaN was treated in HCl:H2O (3:1) solution before metal deposition and annealed at 500°C for 10 minutes in 90% N2 and 0% O2 atmosphere. Similar procedure applied on p-AlxGa1-xN (x = 5-7%), with a hole concentration of 2.3 x 1017 cm-3, yields a ρc of 1.8 x 10-4 Ω cm2. An increase is observed in ρc when Mg doping exceeds 4 x 1019 cm-3 in both p-GaN and p-AlGaN. This is attributed to Mg self compensation. This increase is more pronounced in AlGaN which we attribute to the presence of residual native aluminum oxides.

Journal of Alloys and Compounds

Vacuum, 2019

Abstract We report about chemical, structural and optical characteristics of porous GaAs near-sur... more Abstract We report about chemical, structural and optical characteristics of porous GaAs near-surface layers formed by low energy and high fluence ion implantation of Si+ and Ge+ ions. The energy of implanted ions was 25 keV and the ion dose was 2 × 1016 ion⋅cm−2 for both species. After implantation, experimental samples were annealed under N2 atmosphere resulting in the increment of porosity. The chemical properties of the samples were studied by SIMS and Raman spectroscopy. The Raman spectroscopy was used as well for examining the presence of amorphous phase in a near surface layer caused by ion implantation. The porous GaAs demonstrates visible photoluminescence under ultraviolet excitation. Optical reflection coefficient radically decreases after implantation due to the porous layer formation. The size and in-depth distribution of pores were analyzed by AFM in combination with controlling Ar+ ion etching. Our findings, let us suggests that ion implantation can be used as a reliable technique to prepare porous semiconductors with potential applications for fabrication of optoelectronic devices. The mechanism of pores formation and growth during ion implantation in semiconductors and post-implantation annealing is discussed.

Solid State Ionics, 2018

Abstract Hydration of borosilicate glass (Corning Pyrex glass) in isotopic water H218O vapor was ... more Abstract Hydration of borosilicate glass (Corning Pyrex glass) in isotopic water H218O vapor was performed at different temperatures. The depth distributions of 1H and 18O in the borosilicate glass measured by the Time-of-Flight Secondary Ion Mass-Spectrometry (TOF-SIMS) were found to be drastically different. The activation energies for the 18O diffusion and for the glass hydrogenation were measured experimentally. The depth distribution of the 18O isotope was described well by the complementary error function, whereas the depth distribution of hydrogen represented the so-called “S-curve”. A similar hydrogen distribution was observed earlier in hydrated natural aluminosilicate glasses (obsidians). This led us to the conclusion that the hydrogenated layer was formed due to a solid state chemical reaction between protons and the glass network. The protons were the result of another solid state chemical reaction between the absorbed water molecules and glass network occurring in a top surface layer (

Surface and Interface Analysis

ABSTRACT

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1997

Journal of Non-Crystalline Solids, 2009

Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, 2016

Studies of pattern formation on variable-temperature Ge targets by ion beam sputtering are presen... more Studies of pattern formation on variable-temperature Ge targets by ion beam sputtering are presented. A high-energy heavy polyatomic bismuth ion beam was used to reveal the effect of thermal spikes in the dynamics of pattern formation. By varying the target temperature in the range from 123 to 773 K, different morphologies of the irradiated surfaces were obtained. A smooth surface was observed for a target temperature of 123 K. Sputtering at a target temperature between 300 and 573 K gave rise to poorly oriented dot patterns and resulted in a checkerboard pattern at a target temperature of 773 K. Mechanisms of surface patterning under ion irradiation are discussed.

Journal of Surface Investigation. X-ray, Synchrotron and Neutron Techniques, 2009

The depth distribution profiles of sodium atoms in silicon upon high-voltage implantation (ion en... more The depth distribution profiles of sodium atoms in silicon upon high-voltage implantation (ion energy, 300 keV; implantation dose, 5 × 10 14 and 3 × 10 15 cm-2) are investigated before and after annealing at temperatures in the range T ann = 300-900 °C (t ann = 30 min). Ion implantation is performed with the use of a high-resistivity p-Si (ρ = 3-5 k Ω cm) grown by floating-zone melting. After implantation, the depth distribution profiles are characterized by an intense tail attributed to the incorporation of sodium atoms into channels upon their scattering from displaced silicon atoms. At an implantation dose of 3 × 10 15 ions/cm 2 , which is higher than the amorphization threshold of silicon, a segregation peak is observed on the left slope of the diffusion profile in the vicinity of the maximum after annealing at a temperature T ann = 600 ° C. At an implantation dose of 5 × 10 14 ions/cm 2 , which is insufficient for silicon amorphization, no similar peak is observed. Annealing at a temperature T ann = 700 ° C leads to a shift of the profile toward the surface of the sample. Annealing performed at temperatures T ann ≥ 800 ° C results in a considerable loss of sodium atoms due to their diffusion toward the surface of the sample and subsequent evaporation. After annealing, only a small number of implanted atoms that are located far from the region of the most severe damages remain electrically active. It is demonstrated that, owing to the larger distance between the diffusion source and the surface of the sample, the superficial density of electrically active atoms in the diffusion layer upon high-voltage implantation of sodium ions is almost one order of magnitude higher than the corresponding density observed upon low-voltage implantation (50-70 keV). In this case, the volume concentration of donors near the surface of the sample increases by a factor of 5-10. The measured values of the effective diffusion parameters of sodium at annealing temperatures in the range T ann = 525-900 ° C are as follows: D 0 = 0.018 cm 2 /s and E a = 1.29 eV/kT. These parameters are almost identical to those previously obtained in the case of low-voltage implantation.

Journal of Applied …, 2001

Journal of Crystal Growth, 2011

GaMnAs layers were grown by MBE on GaAs (001) substrates. The structural properties of the epilay... more GaMnAs layers were grown by MBE on GaAs (001) substrates. The structural properties of the epilayers were studied by atomic force microscopy, secondary ion mass spectroscopy, high-resolution X-ray diffraction, and Raman spectroscopy. Photoreflectance spectra at room temperature exhibited Franz–Keldysh oscillations; from an analysis of these oscillations we obtained the built-in internal electric field and the bandgap energy of the GaMnAs

We report on the first attempts of Mg doping of hexagonal InN/Al 2 O 3 (0001) films grown by plas... more We report on the first attempts of Mg doping of hexagonal InN/Al 2 O 3 (0001) films grown by plasma-assisted molecular beam epitaxy. A dramatic improvement of crystalline quality of InN : Mg epilayers has been observed at the magnesium concentration in the 10 19 to 3 Â 10 20 cm ± ±3 range as indicated by triple-crystal X-ray diffraction q-rocking curve peak width below 30 arcsec. An increase of Mg doping higher than 10 21 cm ± ±3 deteriorates dramatically the InN crystal quality and surface morphology. A thermodynamic model of the surfactant Mg effect is proposed. The increase in Mg concentration causes the reduction by an order of magnitude (down to n = 10 19 cm ± ±3) of free electron concentration in InN : Mg layers compared to undoped ones, accompanied by a significant reduction of electron mobility. This behavior can be explained by a complex effect of the crystal quality improvement and the carrier compensation by incorporated Mg acceptors.