Investigation of Si<B, S≥and Si<B, Rh≥compensated photoresistors

The influence of the electric parameters of compensating sulfur and rhodium impurities on the photosensitivity of p-type silicon is discussed in the present paper. Conditions of the increased photosensitivity ofSi<B, S> andSi<B, Rh> in the near-IR region of the spectrum are defined. The increase of the photosensitivity of compensated silicon at 300 K is found to be due to a higher degree of microinhomogeneity in the resistivity (with a simultaneous increase in the degree of compensation) irrespective of the electric parameters of the compensating impurity in silicon. Tashkent State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 77–80, June, 2000.     

Some non‐local problems for the parabolic‐hyperbolic type equation with complex spectral parameter

In the present paper the unique solvability of two non‐local problems for the mixed parabolic‐hyperbolic type equation with complex spectral parameter is proved. Sectors for values of the spectral parameter where these problems have unique solutions are shown. Uniqueness of the solution is proved by the method of energy integral and existence is proved by the method of integral equations. In particular cases, eigenvalues and corresponding eigenfunctions of the studied problems are found. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A Study of the Redistribution Conditions of Carbon Black Particles from the Bulk to the Interface in Heterogeneous Polymer Blends

The redistribution conditions of carbon black particles to the interface between polymers were studied based on the measurement of the value of superadditive conductivity of several heterogeneous polymer blends filled with powdered carbon black. The redistribution of carbon black from the polymer phase that has low ability to wet the powder proceeds efficiently only to the boundary with polymer having better wetting ability. Significant differences in the conditions of particle localization at the boundaries between polymer phases and between two low-molecular-weight liquids arising from the specific features of polymer adsorption were demonstrated.     

Vapor-phase growth of CdF<Subscript>2</Subscript> whiskers in the CdF<Subscript>2</Subscript>-GaF<Subscript>3</Subscript> system

Insulating CdF₂ whiskers of helical shape with a diameter from 10 to 30 μm and a length exceeding 7 mm have been grown for the first time. The conditions of their growth suggest that they grow through the classical vapor-liquid-solid mechanism.     

Stochastic correlation tomography

An analysis is made of the possibility of using stochastic generation of correlated quanta (random in time) to obtain rapid volume information on the state of a medium and to develop the physical principles of a real-time tomograph. Flux theory and mathematical modeling with a computer experiment are successfully used for these investigations.     

Impedance spectroscopic studies of an organic semiconductor device incorporating a thin film of highly doped ZnPc with MoO3

We use experimental results of low signal impedance spectroscopy to investigate the conduction mechanism in organic semiconductor, zinc phthalocyanine (ZnPc). The first 10 nm, of a total of 150 nm thermally deposited ZnPc, was doped with molybdenum oxide (MoO₃) by co-evaporation to obtain a 20% doping concentration. The ac electrical parameters were measured at room temperature in the dc bias and frequency ranges of 0–5 V and 100 Hz–0.1 MHz, respectively. The variation of bulk resistance with applied bias presents a clear indication of space charge limited conduction in the fabricated device. The experimental results show a strong frequency dependence of capacitance and loss tangent at low frequencies and high applied bias, while at higher frequencies and low applied bias a weak dependence is observed. Moreover, the ac conductivity shows a strong dependence on frequency and is found to vary as ω^s with the index s≤1.15 suggesting a dominant hopping mechanism of conduction.     

Interaction of deep impurities with radiation defects in n-Si at γ-irradiation

This work presents the results of research on peculiarities of radiation defect formation in single crystal n-Si, doped by deep level impurities (Cu, Ni, Ir, Rh, Pt and Au), at irradiation by γ-quanta of ⁶⁰Co. A property of γ-irradiation to create only vacancies and self-interstitial atoms is used to understand the nature of deep levels with participation of these impurities and primary elemental radiation defects. The role of covalence radii and diffusion coefficients in efficiency of radiation defect formation is discussed.     

High temperature gate control of quantum well spin memory

Time-resolved optical measurements in (110)-oriented GaAs/AlGaAs quantum wells show a tenfold increase of the spin-relaxation rate as a function of applied electric field from 20 to 80 kV cm(-1) at 170 K and indicate a similar variation at 300 K, in agreement with calculations based on the Rashba effect. Spin relaxation is almost field independent below 20 kV cm(-1) reflecting quantum well interface asymmetry. The results indicate the achievability of a voltage-gateable spin-memory time longer than 3 ns simultaneously with a high electron mobility.     

Investigation of temperature-dependent electrical properties of p-VOPc/n-si heterojunction under dark conditions

An organic/inorganic heterojunction p-VOPc/n-Si was fabricated and its electrical properties were investigated. Temperature-dependent dark current–voltage (I–V) characteristics of the heterojunction exhibited rectification behaviour with a rectification ratio of 405 at ±1 V and room temperature. The current–voltage characteristics of the cell showed ohmic conduction at low voltages followed by a space charge-limited current (SCLC) conduction dominated by an exponential trap distribution at higher voltages. At room temperature, the series and shunt resistances were found to be approximately 1.4 and 100 kΩ, respectively. Diode ideality factor n was found to be 3.2 at room temperature and dropped to 1.9 at 363 K. Room temperature mobility of vanadyl phthalocyanine (VOPc) was extracted from the I–V characteristics in the SCLC region and was found approximately 15.5 × 10⁻³ cm² V⁻¹ s⁻¹. The effective barrier height, Ф_B, was estimated as 0.77 eV. The effect of temperature, on various heterojunction parameters was recorded under dark conditions and at temperatures ranging from 300 to 363 K.