Photoluminescence of a BaSiO3:Yb3+ crystal

We present the results of a study of the luminescence and luminescence excitation spectra, and also the luminescence kinetics of a BaSiO₃:Yb³⁺ crystal. We have established the mechanism for emission by the matrix and energy transfer from the matrix to the rare earth ion. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 478–482, July–August, 2006.     

Optimal coefficient control in parabolic systems

We consider an optimal coefficient control problem for a linear parabolic equation. For this problem, we study well-posedness issues and obtain necessary optimality conditions.     

AC electrical properties of FeIn2S4

The frequency and temperature dependences of the ac capacitance and resistivity of FeIn₂S₄ semiconductors are studied. Resonances are observed at certain temperatures in the frequency range (2.5–5.0) × 10⁵ Hz. The permittivity of the crystals and the activation energy of charge carriers are determined. It is found that electrical conduction in the given temperature interval is governed by an activation mechanism. The activation energy is frequency-dependent, because the relaxation time of barrier layers decreases with rising frequency.     

Currents of isothermal relaxation in GaS〈Yb〉 single crystals

The results of investigation of relaxation processes in highly resistive M-GaS〈Yb〉-M systems at different temperatures are reported. It was shown that falling relaxation of dark current in these systems is accompanied by charge accumulation in deep trapping levels of E_t=0.63eV with concentration of N_t=6×10¹³ cm^-3.     

Electrical conductivity in single crystals of GaSe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Te<Subscript>1 – <Emphasis Type="Italic">x</Emphasis></Subscript> solid solutions in strong electrical fields

This paper presents some results of studying the Poole–Frenkel effect with allowance for shielding in layered GaSe and GaTe single crystals and their solid solutions in strong electrical fields of up to 10⁵ V/cm at temperatures of 103–250 K. According to the relationship \(\left(\frac{\sigma}{\sigma(0)}\right)^{1/2}\) log\(\frac{\sigma}{\sigma(0)} = E\sqrt{\frac{\varepsilon}{4\pi n(0)kT}}\), there exists a linear dependence between \(\left(\frac{\sigma}{\sigma(0)}\right)^{1/2}\) log\(\frac{\sigma}{\sigma(0)}\) and the electrical field E (σ is the electrical conductivity in strong electrical fields, and σ(0) is the electrical conductivity in the ohmic region). The slopes of these lines have been determined at different temperatures (103–250 K) by estimating the concentration of current carriers n(0) = 3 × 10¹³–5 × 10¹⁵ cm^–3 in the ohmic region of the electrical conductivity of solid solutions of layered GaSe _x Te_1–x single crystals (x = 1.00, 0.95, 0.90, 0.80, 0.70, 0.30, 0.20, 0.10, 0).