Vadim Korol' - Academia.edu (original) (raw)

Papers by Vadim Korol'

Physica Status Solidi (a), 1988

Scaffolds of 13-93 bioactive glass (6Na 2 O, 12K 2 O, 5MgO, 20CaO, 4P 2 O 5 , 53SiO 2 ; wt %) wit... more Scaffolds of 13-93 bioactive glass (6Na 2 O, 12K 2 O, 5MgO, 20CaO, 4P 2 O 5 , 53SiO 2 ; wt %) with an oriented pore architecture were formed by unidirectional freezing of camphene-based suspensions, followed by thermal annealing of the frozen constructs to grow the camphene crystals. After sublimation of the camphene, the constructs were sintered (1 h at 700 °C) to produce a dense glass phase with oriented macropores. The objective of this work was to study how constant freezing rates (1-7 °C/min) during the freezing step influenced the pore orientation and mechanical response of the scaffolds. When compared to scaffolds prepared by freezing the suspensions on a substrate kept at a constant temperature of 3 °C (time-dependent freezing rate), higher freezing rates resulted in better pore orientation, a more homogeneous microstructure, and a marked improvement in the mechanical response of the scaffolds in compression. Scaffolds fabricated using a constant freezing rate of 7 °C/min (porosity = 50 ± 4%; average pore diameter = 100 μm), had a compressive strength of 47 ± 5 MPa and an elastic modulus of 11 ± 3 GPa (in the orientation direction). In comparison, scaffolds prepared by freezing on the constant-temperature substrate had strength and modulus values of 35 ± 11 MPa and 8 ± 3 GPa, respectively. These oriented bioactive glass scaffolds prepared by the constant freezing rate route could potentially be used for the repair of defects in load-bearing bones, such as segmental defects in the long bones.

M.N.Belikova, Vadim Korol', 1977

Experiments were performed to study the effects of radiation defects, produced by ion bombardment... more Experiments were performed to study the effects of radiation defects, produced by ion bombardment, in silicon on the electrical activity and diffusion of implanted sodium. The silicon, prepared by a zone melting process, was of p-type with a specific resistance of 0.8-1.5 kiloohms/cm and a dislocation density of 5 x 10 to the 4th/sq cm. It is found possible to control the diffusive flux of fast internodal additives in silicon by means of radiation defects.

Technical Physics, 2013

Experimental data for the variation of the work function on the Si and GaAs semiconductor sur fac... more Experimental data for the variation of the work function on the Si and GaAs semiconductor sur faces irradiated by cesium ions are presented. The formation mechanism of CsM + cluster ions (M is the ana lyte) is considered. Ionization potentials for some CsM molecules are calculated, and a simple experimental technique to determine the concentration of cesium penetrating into the subsurface region of various mate rials during cesium ion sputtering is suggested. This technique uses a preimplanted potassium as an "internal standard."

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 Surface Investigation. X-ray, Synchrotron and Neutron Techniques, 2011

A four point probe method was used to study, as the layers were removed consecutively, the con ce... more A four point probe method was used to study, as the layers were removed consecutively, the con centration distribution profiles of free electrons in high resistivity p Si with implanted P + and Na + ions. Anodic oxidation was used to remove layers at a depth of less than 1 µm, and polishing at larger depths. It was shown that the efficiency of diffusion doping of silicon with sodium is determined, to a large extent, by the ratio between the energies of P + and Na + ions. If the conditions are optimal, the efficiency of doping by simultaneous implantation of sodium and phosphorus ions is better (by a factor of 2.5 on the average) than that of doping with Na + ions only.

Semiconductors, 2008

The effect of oxygen on diffusion of sodium implanted into silicon is studied for the first time ... more The effect of oxygen on diffusion of sodium implanted into silicon is studied for the first time in the temperature range from 500 to 850 ° C. A high-resistivity p-Si (ρ > 1 k Ω cm) grown by the Czochralski method in a magnetic field (mCz) with the oxygen concentration ~3 × 10 17 cm-3 was used. For comparison, we used silicon grown by the crucibleless floating zone method (fz). Temperature dependences of the effective diffusion coefficient of sodium in the mCz-Si and fz-Si crystals were determined and written as D mCz [cm 2 /s] = 1.12exp(-1.64 eV/ kT) cm 2 /s and D fz [cm 2 /s] = 0.024exp(-1.29 eV/ kT) cm 2 /s, respectively. It is assumed that larger values of diffusion parameters in oxygen-containing silicon are caused by formation of complex aggregates that contain sodium and oxygen atoms.

Physica Status Solidi (a), 1989

ABSTRACT Processes of formation and annealing of radiation defects are studied in n-Si grown by t... more ABSTRACT Processes of formation and annealing of radiation defects are studied in n-Si grown by the Czochralski and the float-zone technique with ion-implanted Li and Na. The defects produced by Pu238 -particle irradiation are investigated at Schottky barriers by the DLTS method. From these measurements deep level energies, production rates, capture cross sections, and annealing characteristics are found.[Russian Text Ignore]

Physica Status Solidi (a), 1988

Scaffolds of 13-93 bioactive glass (6Na 2 O, 12K 2 O, 5MgO, 20CaO, 4P 2 O 5 , 53SiO 2 ; wt %) wit... more Scaffolds of 13-93 bioactive glass (6Na 2 O, 12K 2 O, 5MgO, 20CaO, 4P 2 O 5 , 53SiO 2 ; wt %) with an oriented pore architecture were formed by unidirectional freezing of camphene-based suspensions, followed by thermal annealing of the frozen constructs to grow the camphene crystals. After sublimation of the camphene, the constructs were sintered (1 h at 700 °C) to produce a dense glass phase with oriented macropores. The objective of this work was to study how constant freezing rates (1-7 °C/min) during the freezing step influenced the pore orientation and mechanical response of the scaffolds. When compared to scaffolds prepared by freezing the suspensions on a substrate kept at a constant temperature of 3 °C (time-dependent freezing rate), higher freezing rates resulted in better pore orientation, a more homogeneous microstructure, and a marked improvement in the mechanical response of the scaffolds in compression. Scaffolds fabricated using a constant freezing rate of 7 °C/min (porosity = 50 ± 4%; average pore diameter = 100 μm), had a compressive strength of 47 ± 5 MPa and an elastic modulus of 11 ± 3 GPa (in the orientation direction). In comparison, scaffolds prepared by freezing on the constant-temperature substrate had strength and modulus values of 35 ± 11 MPa and 8 ± 3 GPa, respectively. These oriented bioactive glass scaffolds prepared by the constant freezing rate route could potentially be used for the repair of defects in load-bearing bones, such as segmental defects in the long bones.

M.N.Belikova, Vadim Korol', 1977

Experiments were performed to study the effects of radiation defects, produced by ion bombardment... more Experiments were performed to study the effects of radiation defects, produced by ion bombardment, in silicon on the electrical activity and diffusion of implanted sodium. The silicon, prepared by a zone melting process, was of p-type with a specific resistance of 0.8-1.5 kiloohms/cm and a dislocation density of 5 x 10 to the 4th/sq cm. It is found possible to control the diffusive flux of fast internodal additives in silicon by means of radiation defects.

Technical Physics, 2013

Experimental data for the variation of the work function on the Si and GaAs semiconductor sur fac... more Experimental data for the variation of the work function on the Si and GaAs semiconductor sur faces irradiated by cesium ions are presented. The formation mechanism of CsM + cluster ions (M is the ana lyte) is considered. Ionization potentials for some CsM molecules are calculated, and a simple experimental technique to determine the concentration of cesium penetrating into the subsurface region of various mate rials during cesium ion sputtering is suggested. This technique uses a preimplanted potassium as an "internal standard."

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 Surface Investigation. X-ray, Synchrotron and Neutron Techniques, 2011

A four point probe method was used to study, as the layers were removed consecutively, the con ce... more A four point probe method was used to study, as the layers were removed consecutively, the con centration distribution profiles of free electrons in high resistivity p Si with implanted P + and Na + ions. Anodic oxidation was used to remove layers at a depth of less than 1 µm, and polishing at larger depths. It was shown that the efficiency of diffusion doping of silicon with sodium is determined, to a large extent, by the ratio between the energies of P + and Na + ions. If the conditions are optimal, the efficiency of doping by simultaneous implantation of sodium and phosphorus ions is better (by a factor of 2.5 on the average) than that of doping with Na + ions only.

Semiconductors, 2008

The effect of oxygen on diffusion of sodium implanted into silicon is studied for the first time ... more The effect of oxygen on diffusion of sodium implanted into silicon is studied for the first time in the temperature range from 500 to 850 ° C. A high-resistivity p-Si (ρ > 1 k Ω cm) grown by the Czochralski method in a magnetic field (mCz) with the oxygen concentration ~3 × 10 17 cm-3 was used. For comparison, we used silicon grown by the crucibleless floating zone method (fz). Temperature dependences of the effective diffusion coefficient of sodium in the mCz-Si and fz-Si crystals were determined and written as D mCz [cm 2 /s] = 1.12exp(-1.64 eV/ kT) cm 2 /s and D fz [cm 2 /s] = 0.024exp(-1.29 eV/ kT) cm 2 /s, respectively. It is assumed that larger values of diffusion parameters in oxygen-containing silicon are caused by formation of complex aggregates that contain sodium and oxygen atoms.

Physica Status Solidi (a), 1989

ABSTRACT Processes of formation and annealing of radiation defects are studied in n-Si grown by t... more ABSTRACT Processes of formation and annealing of radiation defects are studied in n-Si grown by the Czochralski and the float-zone technique with ion-implanted Li and Na. The defects produced by Pu238 -particle irradiation are investigated at Schottky barriers by the DLTS method. From these measurements deep level energies, production rates, capture cross sections, and annealing characteristics are found.[Russian Text Ignore]