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Volodymyr A. Gnatyuk - One of the best experts on this subject based on the ideXlab platform.

  • effect of Cdte Crystal thickness on the efficiency of cr Cdte au schottky diode detectors
    Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2020
    Co-Authors: V. M. Sklyarchuk, Volodymyr A. Gnatyuk, T. Aoki
    Abstract:

    Abstract The effect of Cdte Crystal thickness on the detection efficiency and energy resolution of Cr/Cdte/Au diode X/ γ -ray detectors has been studied. The Schottky (Cr electrode) and near Ohmic (Au electrode) contacts were created using Ar plasma treatment of the B- and A-faces of Cdte(111) single Crystals at different regimes, respectively. Detector-grade Cdte wafers with an area of 5 × 5 mm2 and thicknesses d of 0.5 mm, 0.75 mm, 1.0 mm and 2.0 mm were used. High energy resolution (FWHM) in the 137Cs spectra (662 keV peak) was achieved: from 0.5 % for thin detectors to 3.0 % for thick ones. From the comparison of the detection efficiency dependences on the Cdte Crystal thickness with the corresponding calculated dependences, the uncompensated impurity concentration in Cdte was obtained as N  ≈  4 × 1010 cm−3. N determines the space–charge region width W in Schottky diodes, therefore the effect of this value on the detection efficiency was analyzed. A key feature of the efficiency calculation was the correct evaluation of the electric field strength in the Crystals and also using the integration limit d rather than W when W > d (in contrast to the earlier works).

  • Effect of Cdte Crystal thickness on the efficiency of Cr/Cdte/Au Schottky-diode detectors
    Nuclear Instruments and Methods in Physics Research Section A: Accelerators Spectrometers Detectors and Associated Equipment, 2020
    Co-Authors: V. M. Sklyarchuk, Volodymyr A. Gnatyuk, T. Aoki
    Abstract:

    Abstract The effect of Cdte Crystal thickness on the detection efficiency and energy resolution of Cr/Cdte/Au diode X/ γ -ray detectors has been studied. The Schottky (Cr electrode) and near Ohmic (Au electrode) contacts were created using Ar plasma treatment of the B- and A-faces of Cdte(111) single Crystals at different regimes, respectively. Detector-grade Cdte wafers with an area of 5 × 5 mm2 and thicknesses d of 0.5 mm, 0.75 mm, 1.0 mm and 2.0 mm were used. High energy resolution (FWHM) in the 137Cs spectra (662 keV peak) was achieved: from 0.5 % for thin detectors to 3.0 % for thick ones. From the comparison of the detection efficiency dependences on the Cdte Crystal thickness with the corresponding calculated dependences, the uncompensated impurity concentration in Cdte was obtained as N  ≈  4 × 1010 cm−3. N determines the space–charge region width W in Schottky diodes, therefore the effect of this value on the detection efficiency was analyzed. A key feature of the efficiency calculation was the correct evaluation of the electric field strength in the Crystals and also using the integration limit d rather than W when W > d (in contrast to the earlier works).

  • Formation of electrical contacts on Cdte Crystals for x-ray detectors performance
    Hard X-Ray and Gamma-Ray Detector Physics VII, 2005
    Co-Authors: Volodymyr A. Gnatyuk, Toru Aoki, Yoshinori Hatanaka, Olexandr I. Vlasenko
    Abstract:

    The procedures of fabrication of electrical contacts and modification of their properties in high-resistivity Cdte:Cl Crystals have been investigated to obtain diodes for nuclear radiation detectors. Excimer laser annealing was utilized to attain heavy In doping of the Cdte surface region. Using various preliminary treatments of the Cdte Crystal surface and studying electrode vacuum deposition procedures and laser processing of Cdte Crystals pre-coated with an In dopant film, the optimal conditions of fabrication of In/Cdte/Au diode structures were elaborated. It was considered that a Schottky barrier at the Au-Cdte contact was formed and a shallow built-in p-n junction at the In-Cdte interface arose as a result of both thermal In diffusion and effect of laser-induced shock waves under irradiation of the samples from the In-contact side. The In/Cdte/Au diodes had sharp I-V characteristics. Laser irradiation remarkably decreased the leakage current and increased the forward current. Moreover, the electrical properties of laser-formed p-n junctions were being improved after storage of the samples. The detectors showed a low leakage current (1-8 nA/cm 2 at 100 V and 300 K), optimal electrical barrier (0.72 eV) and high energy resolution (3.1 keV FWHM at 122 keV at γ-ray peak of Co-57). Variations in leakage currents and radiation detection properties of fabricated Cdte wafers and pixels diced from the wafers were associated with laser stimulated defect formation in the bulk of Cdte and generation of extended defects during the pixels performance. The regimes of injection and recombination in fabricated Cdte diodes have been analyzed.

  • Solid-liquid phase transitions in Cdte Crystals under pulsed laser irradiation
    Applied Physics Letters, 2003
    Co-Authors: Volodymyr A. Gnatyuk, Toru Aoki, O. S. Gorodnychenko, Yoshinori Hatanaka
    Abstract:

    Phase transitions in Cdte Crystals irradiated with nanosecond KrF (248 nm) excimer laser pulses were investigated by a numerical simulation and time-resolved reflectivity method. By solving the time-dependent heat flow equation and taking into account the temperature dependences of semiconductor parameters, the time dependence of the surface temperature in a Cdte Crystal was calculated as a function of laser pulse intensity. The dynamics of laser-induced melting was directly monitored by measurements of the reflection coefficient of a probe laser beam (532 nm). The melting and ablation thresholds have been determined as 2.5 and 7.3 MW/cm2, respectively.

Yoshinori Hatanaka - One of the best experts on this subject based on the ideXlab platform.

  • Formation of electrical contacts on Cdte Crystals for x-ray detectors performance
    Hard X-Ray and Gamma-Ray Detector Physics VII, 2005
    Co-Authors: Volodymyr A. Gnatyuk, Toru Aoki, Yoshinori Hatanaka, Olexandr I. Vlasenko
    Abstract:

    The procedures of fabrication of electrical contacts and modification of their properties in high-resistivity Cdte:Cl Crystals have been investigated to obtain diodes for nuclear radiation detectors. Excimer laser annealing was utilized to attain heavy In doping of the Cdte surface region. Using various preliminary treatments of the Cdte Crystal surface and studying electrode vacuum deposition procedures and laser processing of Cdte Crystals pre-coated with an In dopant film, the optimal conditions of fabrication of In/Cdte/Au diode structures were elaborated. It was considered that a Schottky barrier at the Au-Cdte contact was formed and a shallow built-in p-n junction at the In-Cdte interface arose as a result of both thermal In diffusion and effect of laser-induced shock waves under irradiation of the samples from the In-contact side. The In/Cdte/Au diodes had sharp I-V characteristics. Laser irradiation remarkably decreased the leakage current and increased the forward current. Moreover, the electrical properties of laser-formed p-n junctions were being improved after storage of the samples. The detectors showed a low leakage current (1-8 nA/cm 2 at 100 V and 300 K), optimal electrical barrier (0.72 eV) and high energy resolution (3.1 keV FWHM at 122 keV at γ-ray peak of Co-57). Variations in leakage currents and radiation detection properties of fabricated Cdte wafers and pixels diced from the wafers were associated with laser stimulated defect formation in the bulk of Cdte and generation of extended defects during the pixels performance. The regimes of injection and recombination in fabricated Cdte diodes have been analyzed.

  • Solid-liquid phase transitions in Cdte Crystals under pulsed laser irradiation
    Applied Physics Letters, 2003
    Co-Authors: Volodymyr A. Gnatyuk, Toru Aoki, O. S. Gorodnychenko, Yoshinori Hatanaka
    Abstract:

    Phase transitions in Cdte Crystals irradiated with nanosecond KrF (248 nm) excimer laser pulses were investigated by a numerical simulation and time-resolved reflectivity method. By solving the time-dependent heat flow equation and taking into account the temperature dependences of semiconductor parameters, the time dependence of the surface temperature in a Cdte Crystal was calculated as a function of laser pulse intensity. The dynamics of laser-induced melting was directly monitored by measurements of the reflection coefficient of a probe laser beam (532 nm). The melting and ablation thresholds have been determined as 2.5 and 7.3 MW/cm2, respectively.

S H Tang - One of the best experts on this subject based on the ideXlab platform.

  • photon energy and carrier density dependence of spin dynamics in bulk Cdte Crystal at room temperature
    Applied Physics Letters, 2009
    Co-Authors: Zuanming Jin, Weiming Liu, S H Tang
    Abstract:

    Excitation photon energy and carrier density dependence of spin dynamics in bulk Cdte Crystal was studied by time resolved pump-probe reflectivity technique at room temperature. The results show that spin relaxation time decreases monotonously. While with increasing excitation carrier density, the time constants increases initially then decreases after reaching a maximum value. Our experimental results reveal that both D’yakonov–Perel’ [M. I. D’yakonov and V. I. Perel’, Sov. Phys. JETP 38, 177 (1974)] and Elliot–Yafet [R. J. Elliott, Phys. Rev. 96, 266 (1954); Y. Yafet, Solid State Phys. 14, 1 (1963)] mechanisms dominate the spin relaxation process in Cdte Crystal.

Xi-cheng Zhang - One of the best experts on this subject based on the ideXlab platform.

T. Aoki - One of the best experts on this subject based on the ideXlab platform.

  • effect of Cdte Crystal thickness on the efficiency of cr Cdte au schottky diode detectors
    Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2020
    Co-Authors: V. M. Sklyarchuk, Volodymyr A. Gnatyuk, T. Aoki
    Abstract:

    Abstract The effect of Cdte Crystal thickness on the detection efficiency and energy resolution of Cr/Cdte/Au diode X/ γ -ray detectors has been studied. The Schottky (Cr electrode) and near Ohmic (Au electrode) contacts were created using Ar plasma treatment of the B- and A-faces of Cdte(111) single Crystals at different regimes, respectively. Detector-grade Cdte wafers with an area of 5 × 5 mm2 and thicknesses d of 0.5 mm, 0.75 mm, 1.0 mm and 2.0 mm were used. High energy resolution (FWHM) in the 137Cs spectra (662 keV peak) was achieved: from 0.5 % for thin detectors to 3.0 % for thick ones. From the comparison of the detection efficiency dependences on the Cdte Crystal thickness with the corresponding calculated dependences, the uncompensated impurity concentration in Cdte was obtained as N  ≈  4 × 1010 cm−3. N determines the space–charge region width W in Schottky diodes, therefore the effect of this value on the detection efficiency was analyzed. A key feature of the efficiency calculation was the correct evaluation of the electric field strength in the Crystals and also using the integration limit d rather than W when W > d (in contrast to the earlier works).

  • Effect of Cdte Crystal thickness on the efficiency of Cr/Cdte/Au Schottky-diode detectors
    Nuclear Instruments and Methods in Physics Research Section A: Accelerators Spectrometers Detectors and Associated Equipment, 2020
    Co-Authors: V. M. Sklyarchuk, Volodymyr A. Gnatyuk, T. Aoki
    Abstract:

    Abstract The effect of Cdte Crystal thickness on the detection efficiency and energy resolution of Cr/Cdte/Au diode X/ γ -ray detectors has been studied. The Schottky (Cr electrode) and near Ohmic (Au electrode) contacts were created using Ar plasma treatment of the B- and A-faces of Cdte(111) single Crystals at different regimes, respectively. Detector-grade Cdte wafers with an area of 5 × 5 mm2 and thicknesses d of 0.5 mm, 0.75 mm, 1.0 mm and 2.0 mm were used. High energy resolution (FWHM) in the 137Cs spectra (662 keV peak) was achieved: from 0.5 % for thin detectors to 3.0 % for thick ones. From the comparison of the detection efficiency dependences on the Cdte Crystal thickness with the corresponding calculated dependences, the uncompensated impurity concentration in Cdte was obtained as N  ≈  4 × 1010 cm−3. N determines the space–charge region width W in Schottky diodes, therefore the effect of this value on the detection efficiency was analyzed. A key feature of the efficiency calculation was the correct evaluation of the electric field strength in the Crystals and also using the integration limit d rather than W when W > d (in contrast to the earlier works).

  • Mass transfer of indium in the In-Cdte structure under nanosecond laser irradiation
    Physics of the Solid State, 2010
    Co-Authors: V. P. Veleshchuk, A. I. Vlasenko, A. Baĭdullaeva, V. A. Gnatyuk, B. K. Dauletmuratov, S. N. Levitskii, O. V. Lyashenko, T. Aoki
    Abstract:

    The features of mass transfer of indium in high-resistance Cdte Crystals under nanosecond irradiation of the In-Cdte structure by laser pulses have been studied and analyzed. The mass transfer coefficients are determined and the average transfer rate of the indium atoms in Cdte under irradiation is evaluated. It is assumed that the concentration diffusion of indium in Cdte and the transfer of impurity atoms by the front of the laser-induced shock wave are not dominant mechanisms of mass transfer under dynamic doping. The most probable process, which provides the formation of the inverse layer in the surface region of the Cdte Crystal under nanosecond laser irradiation of the In film, is an transfer of interstitial In atoms due to the thermal fluctuation jumps under the action of the driving force of the thermoelastic stresses and temperature gradient.