ISSN 1087-6596, Glass Physics and Chemistry, 2006, Vol. 32, No. 5, pp. 529–532. © Pleiades Publishing, Inc., 2006. Original Russian Text © V.A. Bordovskii, G.I. Grabko, R.A. Castro, T.V. Taturevich, 2006, published in Fizika i Khimiya Stekla. 529 INTRODUCTION Amorphous and vitreous chalcogenide semiconduc- tors by their electrical properties (such as the high resis- tivity and photosensitivity) can serve as model objects for use in investigating the specific features of the elec- tronic processes occurring in disordered materials [1, 2]. At present, the relaxation methods employed in studies of various materials under illumination and in the dark have been intensively used in investigating the properties of vitreous chalcogenide semiconductors and in searching for new applications of these materials in practice [3–6]. The investigation of the long-term relaxation of the dark current gives an opportunity to elucidate the mechanisms responsible for the accumu- lation and relaxation of electric charges in the metal– amorphous semiconductor structures [7], as well as to examine their dielectric properties. The purpose of this work was to investigate the dis- persion of the permittivity ε' and the dielectric loss tan- gent tanδ for amorphous layers of the composition As x Se 1 – x (x = 0.4, 0.5) in the frequency range from 10 -3 to 10 –1 Hz. SAMPLE PREPARATION AND EXPERIMENTAL TECHNIQUE The isothermal relaxation curves of the dark current I(t) were measured using As 2 Se 3 and AsSe amorphous films ~1.0 μm thick prepared through thermal evapora- tion under vacuum. The samples had a sandwich-like shape with aluminum electrodes and a contact area of 14.0 mm 2 . The isothermal relaxation curves were recorded using a V7-30 electrometric amplifier and a plotter [8]. The relative error of the measurement of the electric current I(t) did not exceed ±5%. The dispersion of the permittivity ε' and the dielectric loss tangent tanδ was investigated by measuring the isothermal polariza- tion currents I(t) in the temperature range from 293 to 344 K with the subsequent calculation of the depen- dences ε'( f ) and tanδ( f ), where f is the equivalent fre- quency. The largest relative error of the calculation did not exceed ± 4%. RESULTS AND DISCUSSION For the majority of the samples of both composi- tions, the dark current decays in accordance with the power law I = At –n (n = 0.35–0.99). As was shown by Lushcheikin [9], this functional dependence of the polarization current on the time t permits the use of approximate methods for calculating the permittivity ε' and the dielectric loss tangent tanδ. In particular, the dielectric loss factor can be calculated according to the relationship (1) where I p is the polarization current, C 0 is the geometric capacitance, and U 0 is the polarizing voltage. The equivalent frequency can be calculated from the rela- tionship f = 0.1/t. The permittivity ε' was calculated with the use of a satisfactory analytical function that relates the permit- tivity to the polarization current through the expression (2) where ε'( f 0 ) is the permittivity measured after the struc- ture was held under voltage for a time t 0 . In order to obtain the dependence ε'( f ), the frequency was calcu- lated from the relationship f = (0.04 + 0.05n)/t. ε'' I p /2 π fC 0 U 0 , = ε' ε' f 0 ( ) I p t 1 n – t 0 1 n – – ( ) / C 0 U 0 1 n – ( ) , + = Analysis of the Low-Frequency Dispersion of the Dielectric Parameters in As x Se 1 – x Amorphous Layers V. A. Bordovskii, G. I. Grabko, R. A. Castro, and T. V. Taturevich Herzen Russian State Pedagogical University, nab. Reki Moiki 48, St. Petersburg, 191186 Russia e-mail: recastro@fromru.com Received December 29, 2005 Abstract—This paper reports on the results of the investigation into the dispersion of the permittivity ε' and the dielectric loss tangent tanδ for amorphous layers in the As x Se 1 – x system (x = 0.4, 0.5) in the frequency range from 10 –3 to 10 –1 Hz. It is found that the permittivity increases with a decrease in the frequency of the polarizing field due to the possible effect exerted by defect surface states on the polarization processes occurring in the layers of this system. The shape of the Cole–Cole plots indicates the existence of several groups of relaxation oscillators that are responsible for the relaxation processes observed in this frequency range. DOI: 10.1134/S1087659606050063