H. Vydyanath - Academia.edu (original) (raw)
Papers by H. Vydyanath
Semiannual Technical Report, 1981
Electron Mobility at 77K as a Function of the Electron concentration fnr the Iodine Doped Hgo,aCd... more Electron Mobility at 77K as a Function of the Electron concentration fnr the Iodine Doped Hgo,aCd o, 21e Samples. 11 3 Calculated defec concentrations ([e l l, [h • ], [1Te], [(ITeVHg)ll and ^VH 1) as a function of the partial pressure of fig for iodine doped Hgo. eCd o, 2Te annealed at 600°C and quenched to room temperature, calculated electron and hole concentrations expected at 77 K (indicated by solid and dashed lines respectively) are also shown along with the ex perimental points. .. .. .
Journal of Physics and Chemistry of Solids, 1973
Iodine doped single crystals of CdS were grown from the vapor phase. High temperature Hall effect... more Iodine doped single crystals of CdS were grown from the vapor phase. High temperature Hall effect measurements for the crystals equilibrated with Cd and S~ vapors at temperatures between 700 and 1000~ gave the free electron concentration as a function ofpcd or p,.~ and temperature. The results can be explained on the basis of a model in which the CdS is saturated with iodine at low Pcd (= high Psi) but unsaturated at high Pcd. The solubility of iodine in CdS is given by 22-1/8 cl = 1"73 • 10 Ps~ exp (-1.045 eV/kT) cm-3 atm-l/s = 4.62 x 1019 p~ exp (-0.195 eV/kT) cm-~ atm~/4 The formation of pairs (lsVcd)' from I~ and Vc' ~ is governed by the equilibrium constant Ke~.w = 4exp(~< 1.1 eV/kT) If Cd diffusion occurs primarily by free vacancies, the Cd* tracer self diffusion leads to a vacancy mobility of (1.2-0-5) • 10-5 cm ~ sec-~ at 900~ in agreement with results reported by Woodbury [ 12], but (7 ___ 3) times larger than reported by Kumar and Kroger [10].
Intermediate goal of this investigation to correlate nature and concentration of lattice defects ... more Intermediate goal of this investigation to correlate nature and concentration of lattice defects with physicochemical conditions of preparation; namely, temperature, partial pressures of constituent elements and/or dopant concentration. Result of this investigation: possible to predict and control nature and concentration of defects as function of preparation conditions.
Micron (1969), 1970
Abstract Sheet samples of Inconel 600 alloy (76% Ni, 16% Cr, 7% Fe) and Chromel-A alloy (78% Ni, ... more Abstract Sheet samples of Inconel 600 alloy (76% Ni, 16% Cr, 7% Fe) and Chromel-A alloy (78% Ni, 20% Cr) were simultaneously shock-loaded in sandwich assemblies at pressures of 80, 180, 240 and 460 kilobars. The residual defect structures in Inconel 600 and Chromel-A were characterised by planar dislocation arrays exhibiting a prominence of dislocation loops and dipoles. Deformation twins having an average width of 150A were observed to nucleate in the shock-loaded Inconel 600 in the pressure range 200–240kb, while the critical twinning pressure for the Chromel-A was roughly 240kb. Twin volume densities at 240kb were observed to be 14 and 5 per cent for the Inconel and Chromel respectively, and at 460kb the corresponding volume density of twinned material was 24 and 18 per cent respectively. A detailed comparison of the microstructures revealed that prismatic dislocations in the Inconel and Chromel are the most likely sources of deformation microtwins for shock pressures above the critical twinning pressure. This evidence suggests that a pole mechanism for twin formation is increasingly prominent in shock deformed materials of high stacking-fault energy (> 25ergs/cm2), and that twinning in shock-loaded nickel is probably completely dependent upon prismatic twin sources.
Materials Science Forum, 1997
Scripta Metallurgica, 1970
In a study of the thermal recovery of shock-loaded type 304 stainless steel, Murr and Rose (1) ob... more In a study of the thermal recovery of shock-loaded type 304 stainless steel, Murr and Rose (1) observed that for samples annealed at temperature for 0.1 hr., the recovery was noticeably greater at 850°C following shock-loading at 750 and 1200 kilobars, as compared with samples shock-loaded in the pressure range 120-425 kilobars. These
Physica Status Solidi (b), 1968
Skip to Main Content. ...
Journal of Solid State Chemistry, 1975
... Phys. Semi cond. 5, 244 (1971).7. LJ VAN DER PAULA, Philips Tech. Rev. 20, 220 (1959).. ... 1... more ... Phys. Semi cond. 5, 244 (1971).7. LJ VAN DER PAULA, Philips Tech. Rev. 20, 220 (1959).. ... 14, 44 (1975).11. RH BuEE, Phys. Rev. 98, 431 (1955); CZ VAN DOORN AND D. DE NOBEL, Physica 22, 338 (1956); PW DAMS AND TS SHILLIDAY, Bull. Amer. Phys. Soc. ...
Journal of Physics and Chemistry of Solids, 1975
High-temperature Hall effect measurements are carried out on CdS doped with 2.5 X 10"-2.3 X 10" A... more High-temperature Hall effect measurements are carried out on CdS doped with 2.5 X 10"-2.3 X 10" Ag cm-" under various cadmium and sulfur pressures. At high pcd and low silver concentrations, Ag acts as a donor. At higher concentrations self compensation occurs. An anomalous variation of the Hall coefficient with pSI indicates that the electron concentration increases with increasing ps2 This is attributed to +e formation of anti structure defects S,,. A complete defect model is proposed, and published solubility and diffusion data for Ag in CdS in equilibrium with (Ag, Cd) alloys are reinterpreted on the basis of this model.
Journal of Applied Physics, 1976
Hall‐effect and solubility measurements are carried out on Cd‐doped PbTe crystals equilibrated wi... more Hall‐effect and solubility measurements are carried out on Cd‐doped PbTe crystals equilibrated with (Pb,Cd) alloys of various compositions at T=700 and 800 °C and quenched to room temperature. In Pb‐saturated conditions, while most of the Cd is found to be incorporated as neutral Cd on Pb sites CdxPb, a fraction of the total amount of Cd is present as positively charged interstitial species Cdi compensated by electrons. A complete defect model which can predict the behavior of Cd‐doped PbTe in Cd‐rich atmospheres as well as in Te‐rich atmospheres is proposed.
Journal of Applied Physics, 1976
Pb0.8Sn0.2Te single crystals are equilibrated with (Pb0.8Sn0.2)x Cd1-x alloys of various composit... more Pb0.8Sn0.2Te single crystals are equilibrated with (Pb0.8Sn0.2)x Cd1-x alloys of various compositions at 700 and 800 °C and quenched to room temperature. Cd solubility and Hall-effect measurements as a function of the activity of Cd have led to the development of a defect model for Cd-doped Pb0.8Sn0.2Te according to which most of the Cd is present as neutral CdxPb, a small fraction being present as positively charged Cdi compensated by negatively charged vacancies of Pb, V'Pb. The model can also be used to predict the behavior of Cd-doped Pb0.8Sn0.2Te in Cd-rich atmospheres and Te-rich atmospheres.
Journal of Applied Physics, 1976
PbTe single crystals are equilibrated with (Pb,Zn) alloys of various compositions at 700 and 800 ... more PbTe single crystals are equilibrated with (Pb,Zn) alloys of various compositions at 700 and 800 °C and quenched to room temperature. Hall-effect and solubility measurements of these crystals indicate that zinc acts as a donor in PbTe, being incorporated in interstitial sites as Zni compensated by electrons. A complete defect model for Zn-doped PbTe is arrived at, which predicts the behavior of PbTe crystals in metal-rich as well as Te-rich atmospheres.
Journal of Electronic Materials, 1997
The results of arsenic incorporation in HgCdTe layers grown by molecular beam epitaxy (MBE) are r... more The results of arsenic incorporation in HgCdTe layers grown by molecular beam epitaxy (MBE) are reported. Obtained results indicate that arsenic was successfully incorporated as acceptors in MBE-HgCdTe layers after a low temperature anneal. Secondary ion mass spectrometry and Hall effect measurements confirm that arsenic is incorporated with an activation yield of up to 100%. This work confirms that arsenic
Journal of The Electrochemical Society, 1981
The liquidus temperatures for have been determined for, , and compositions by differential therma... more The liquidus temperatures for have been determined for, , and compositions by differential thermal analyses. films with compositions of have been grown by liquid phase epitaxy on (111) A oriented substrates. The Cd segregation coefficient has been determined to be . Films grown at around 550°C from 3 mm thick melts at slow cooling rates showed thicknesses close to those expected for equilibrium growth. The residual impurity in the LPE films was usually n‐type and was less than 1015 cm−3 in the better films. Photovoltaic diodes fabricated in the films have shown performance comparable to those fabricated in bulk grown crystals.
Proceedings, annual meeting, Electron Microscopy Society of America
Inconel specimens explosively shock-loaded to pressures of 80 and 460 Kb were annealed at tempera... more Inconel specimens explosively shock-loaded to pressures of 80 and 460 Kb were annealed at temperatures of 700°C and 800°C for 1 hour, and the recovery of the shocked structures was followed by hardness, and electron microscopy observations.The initial (as-shocked) 80 Kb specimens were characterized by dense networks of dislocations with long dipoles, superjogs, etc., as shown in Fig. 1(a), whereas the as-shocked 460 Kb specimens were profusely twinned [Fig. 1(b)], the twin volume percent being 24%. The Vickers hardness numbers for the 80 and 460 Kb specimens were 265 VHN and 432 VHN respectively, an increase of 16% and 92% respectively with respect to their unshocked hardness values.
Chemischer Informationsdienst
Chemischer Informationsdienst
MRS Proceedings, 1981
EXTENDED ABSTRACTUsing a law of mass action approach in which lattice defects are treated as chem... more EXTENDED ABSTRACTUsing a law of mass action approach in which lattice defects are treated as chemical species, the variation of the defect concentrations as a function of .the physicochemical conditions of preparation has been established via measurements of electrical characteristics which are directly related to the defect concentrations.
Semiannual Technical Report, 1981
Electron Mobility at 77K as a Function of the Electron concentration fnr the Iodine Doped Hgo,aCd... more Electron Mobility at 77K as a Function of the Electron concentration fnr the Iodine Doped Hgo,aCd o, 21e Samples. 11 3 Calculated defec concentrations ([e l l, [h • ], [1Te], [(ITeVHg)ll and ^VH 1) as a function of the partial pressure of fig for iodine doped Hgo. eCd o, 2Te annealed at 600°C and quenched to room temperature, calculated electron and hole concentrations expected at 77 K (indicated by solid and dashed lines respectively) are also shown along with the ex perimental points. .. .. .
Journal of Physics and Chemistry of Solids, 1973
Iodine doped single crystals of CdS were grown from the vapor phase. High temperature Hall effect... more Iodine doped single crystals of CdS were grown from the vapor phase. High temperature Hall effect measurements for the crystals equilibrated with Cd and S~ vapors at temperatures between 700 and 1000~ gave the free electron concentration as a function ofpcd or p,.~ and temperature. The results can be explained on the basis of a model in which the CdS is saturated with iodine at low Pcd (= high Psi) but unsaturated at high Pcd. The solubility of iodine in CdS is given by 22-1/8 cl = 1"73 • 10 Ps~ exp (-1.045 eV/kT) cm-3 atm-l/s = 4.62 x 1019 p~ exp (-0.195 eV/kT) cm-~ atm~/4 The formation of pairs (lsVcd)' from I~ and Vc' ~ is governed by the equilibrium constant Ke~.w = 4exp(~< 1.1 eV/kT) If Cd diffusion occurs primarily by free vacancies, the Cd* tracer self diffusion leads to a vacancy mobility of (1.2-0-5) • 10-5 cm ~ sec-~ at 900~ in agreement with results reported by Woodbury [ 12], but (7 ___ 3) times larger than reported by Kumar and Kroger [10].
Intermediate goal of this investigation to correlate nature and concentration of lattice defects ... more Intermediate goal of this investigation to correlate nature and concentration of lattice defects with physicochemical conditions of preparation; namely, temperature, partial pressures of constituent elements and/or dopant concentration. Result of this investigation: possible to predict and control nature and concentration of defects as function of preparation conditions.
Micron (1969), 1970
Abstract Sheet samples of Inconel 600 alloy (76% Ni, 16% Cr, 7% Fe) and Chromel-A alloy (78% Ni, ... more Abstract Sheet samples of Inconel 600 alloy (76% Ni, 16% Cr, 7% Fe) and Chromel-A alloy (78% Ni, 20% Cr) were simultaneously shock-loaded in sandwich assemblies at pressures of 80, 180, 240 and 460 kilobars. The residual defect structures in Inconel 600 and Chromel-A were characterised by planar dislocation arrays exhibiting a prominence of dislocation loops and dipoles. Deformation twins having an average width of 150A were observed to nucleate in the shock-loaded Inconel 600 in the pressure range 200–240kb, while the critical twinning pressure for the Chromel-A was roughly 240kb. Twin volume densities at 240kb were observed to be 14 and 5 per cent for the Inconel and Chromel respectively, and at 460kb the corresponding volume density of twinned material was 24 and 18 per cent respectively. A detailed comparison of the microstructures revealed that prismatic dislocations in the Inconel and Chromel are the most likely sources of deformation microtwins for shock pressures above the critical twinning pressure. This evidence suggests that a pole mechanism for twin formation is increasingly prominent in shock deformed materials of high stacking-fault energy (> 25ergs/cm2), and that twinning in shock-loaded nickel is probably completely dependent upon prismatic twin sources.
Materials Science Forum, 1997
Scripta Metallurgica, 1970
In a study of the thermal recovery of shock-loaded type 304 stainless steel, Murr and Rose (1) ob... more In a study of the thermal recovery of shock-loaded type 304 stainless steel, Murr and Rose (1) observed that for samples annealed at temperature for 0.1 hr., the recovery was noticeably greater at 850°C following shock-loading at 750 and 1200 kilobars, as compared with samples shock-loaded in the pressure range 120-425 kilobars. These
Physica Status Solidi (b), 1968
Skip to Main Content. ...
Journal of Solid State Chemistry, 1975
... Phys. Semi cond. 5, 244 (1971).7. LJ VAN DER PAULA, Philips Tech. Rev. 20, 220 (1959).. ... 1... more ... Phys. Semi cond. 5, 244 (1971).7. LJ VAN DER PAULA, Philips Tech. Rev. 20, 220 (1959).. ... 14, 44 (1975).11. RH BuEE, Phys. Rev. 98, 431 (1955); CZ VAN DOORN AND D. DE NOBEL, Physica 22, 338 (1956); PW DAMS AND TS SHILLIDAY, Bull. Amer. Phys. Soc. ...
Journal of Physics and Chemistry of Solids, 1975
High-temperature Hall effect measurements are carried out on CdS doped with 2.5 X 10"-2.3 X 10" A... more High-temperature Hall effect measurements are carried out on CdS doped with 2.5 X 10"-2.3 X 10" Ag cm-" under various cadmium and sulfur pressures. At high pcd and low silver concentrations, Ag acts as a donor. At higher concentrations self compensation occurs. An anomalous variation of the Hall coefficient with pSI indicates that the electron concentration increases with increasing ps2 This is attributed to +e formation of anti structure defects S,,. A complete defect model is proposed, and published solubility and diffusion data for Ag in CdS in equilibrium with (Ag, Cd) alloys are reinterpreted on the basis of this model.
Journal of Applied Physics, 1976
Hall‐effect and solubility measurements are carried out on Cd‐doped PbTe crystals equilibrated wi... more Hall‐effect and solubility measurements are carried out on Cd‐doped PbTe crystals equilibrated with (Pb,Cd) alloys of various compositions at T=700 and 800 °C and quenched to room temperature. In Pb‐saturated conditions, while most of the Cd is found to be incorporated as neutral Cd on Pb sites CdxPb, a fraction of the total amount of Cd is present as positively charged interstitial species Cdi compensated by electrons. A complete defect model which can predict the behavior of Cd‐doped PbTe in Cd‐rich atmospheres as well as in Te‐rich atmospheres is proposed.
Journal of Applied Physics, 1976
Pb0.8Sn0.2Te single crystals are equilibrated with (Pb0.8Sn0.2)x Cd1-x alloys of various composit... more Pb0.8Sn0.2Te single crystals are equilibrated with (Pb0.8Sn0.2)x Cd1-x alloys of various compositions at 700 and 800 °C and quenched to room temperature. Cd solubility and Hall-effect measurements as a function of the activity of Cd have led to the development of a defect model for Cd-doped Pb0.8Sn0.2Te according to which most of the Cd is present as neutral CdxPb, a small fraction being present as positively charged Cdi compensated by negatively charged vacancies of Pb, V'Pb. The model can also be used to predict the behavior of Cd-doped Pb0.8Sn0.2Te in Cd-rich atmospheres and Te-rich atmospheres.
Journal of Applied Physics, 1976
PbTe single crystals are equilibrated with (Pb,Zn) alloys of various compositions at 700 and 800 ... more PbTe single crystals are equilibrated with (Pb,Zn) alloys of various compositions at 700 and 800 °C and quenched to room temperature. Hall-effect and solubility measurements of these crystals indicate that zinc acts as a donor in PbTe, being incorporated in interstitial sites as Zni compensated by electrons. A complete defect model for Zn-doped PbTe is arrived at, which predicts the behavior of PbTe crystals in metal-rich as well as Te-rich atmospheres.
Journal of Electronic Materials, 1997
The results of arsenic incorporation in HgCdTe layers grown by molecular beam epitaxy (MBE) are r... more The results of arsenic incorporation in HgCdTe layers grown by molecular beam epitaxy (MBE) are reported. Obtained results indicate that arsenic was successfully incorporated as acceptors in MBE-HgCdTe layers after a low temperature anneal. Secondary ion mass spectrometry and Hall effect measurements confirm that arsenic is incorporated with an activation yield of up to 100%. This work confirms that arsenic
Journal of The Electrochemical Society, 1981
The liquidus temperatures for have been determined for, , and compositions by differential therma... more The liquidus temperatures for have been determined for, , and compositions by differential thermal analyses. films with compositions of have been grown by liquid phase epitaxy on (111) A oriented substrates. The Cd segregation coefficient has been determined to be . Films grown at around 550°C from 3 mm thick melts at slow cooling rates showed thicknesses close to those expected for equilibrium growth. The residual impurity in the LPE films was usually n‐type and was less than 1015 cm−3 in the better films. Photovoltaic diodes fabricated in the films have shown performance comparable to those fabricated in bulk grown crystals.
Proceedings, annual meeting, Electron Microscopy Society of America
Inconel specimens explosively shock-loaded to pressures of 80 and 460 Kb were annealed at tempera... more Inconel specimens explosively shock-loaded to pressures of 80 and 460 Kb were annealed at temperatures of 700°C and 800°C for 1 hour, and the recovery of the shocked structures was followed by hardness, and electron microscopy observations.The initial (as-shocked) 80 Kb specimens were characterized by dense networks of dislocations with long dipoles, superjogs, etc., as shown in Fig. 1(a), whereas the as-shocked 460 Kb specimens were profusely twinned [Fig. 1(b)], the twin volume percent being 24%. The Vickers hardness numbers for the 80 and 460 Kb specimens were 265 VHN and 432 VHN respectively, an increase of 16% and 92% respectively with respect to their unshocked hardness values.
Chemischer Informationsdienst
Chemischer Informationsdienst
MRS Proceedings, 1981
EXTENDED ABSTRACTUsing a law of mass action approach in which lattice defects are treated as chem... more EXTENDED ABSTRACTUsing a law of mass action approach in which lattice defects are treated as chemical species, the variation of the defect concentrations as a function of .the physicochemical conditions of preparation has been established via measurements of electrical characteristics which are directly related to the defect concentrations.