DIELECTRIC PROPERTIES OF Se-Te-In GLASSES
Frequency and temperature dependence of dielectric parameters in chalcogenide glasses Se85-xTe15Inx (x= 0, 2, 6, 10) have been studied by measuring capacitance and conductance in the frequency range 2 kHz to 50 kHz and temperature range 223K to 293K. Results indicate that dielectric dispersion occurs in this frequency and temperature range and dielectric dispersion is more at lower frequency. Dielectric constant and dielectric loss are found to be highly frequency and temperature dependent. The analysis shows that dielectric losses are dipolar in nature and are explained on the basis of Guintini's theory of dielectric dispersion based on two electron hopping over a potential barrier. It has been found that both dielectric constant and dielectric loss are found to increase with increase in Indium concentration and is due to the increase in defect states with increase in Indium concentration. Chalcogenide glasses have been extensively studied due to their varied applications in solid state devices. Selenium tellurium based chalcogenides have been widely studied due to their (a) great storage capacity and fast access to information (b) the advantage to delete and introduce new information (c) electro-photographic applications such as photoreceptors in photocopying and laser printing (1). The study of dielectric behavior of chalcogenide glasses reveals the structural information which may be used to understand the conduction mechanisms. In addition, a study of temperature and frequency dependent dielectric constant may be of importance to understand the nature and origin of losses occurring in these materials. The effect of an impurity in an amorphous semiconductor may be widely different, depending on the conduction mechanism and the structure of material (2).The impurity may either destroy the dangling bond centres of one sign or form charged centres which are compensated by centres of opposite sign. So, the composition dependence of physical parameters like dielectric constant and dielectric loss becomes an area of interest. The present paper reports the frequency and temperature dependence of dielectric constant and dielectric loss in Se85-xTe15Inx (x=0, 2, 6, 10 ) in the temperature range 223K to 293K and frequency range from 2kHz to 50kHz. The results have been analysed in terms of the existing Guintini's theory (3) of dielectric relaxation in chalcogenide glasses. 2. Experimental Details For the present work the glassy materials were prepared by taking the constituent elements (5N pure) in the required atomic weight percentages using electronic balance with an accuracy of 0.0001gm. The weighed components for the respective samples were put into properly cleaned (rinsed with soap solution, acetone and methanol) quartz ampoules. The ampoules were sealed in a vacuum of order of 10 -5 mbar using diffusion pump. The sealed ampoules were heated upto 650 0 C