Indian Journal of Pure & Applied Physics Vol. 49, August 2011, pp. 545-549 Effect of Sb incorporation on the density of defect states in a-Se 90 In 10 glassy alloy S Shukla, S P Singh & S Kumar** Department of Physics, Christ Church College, Kanpur 208 001, India **E-mail: dr_santosh_kr@yahoo.com Received 11 March 2010 ; revised 8 February 2011 ; accepted 20 April 2011 The dc conductivity of thin films of Se 90 In 10-x Sb x (where x =0, 2, 4 and 6) glassy alloys prepared by conventional rapid melt-quenching technique at high electric fields, has been measured. Thin films of amorphous binary and ternary chalcogenide glassy alloys of Se 90 In 10-x Sb x system are obtained by the thermal evaporation technique of bulk material on to well cleaned glass substrates. Current-voltage (I-V) characteristics have been measured at various fixed temperatures. In these samples, ohmic behaviour is observed at low electric fields. However, at high electric fields (E~10 4 V/cm), non-ohmic behaviour is observed. An analysis of the experimental data confirms the presence of space charge limited conduction (SCLC) in the glassy materials studied in the present case. From the fitting of the data to the theory of SCLC, the density of defect states (DOS) near Fermi level has been calculated. It is found that the DOS is increasing with increase in concentration of Sb in pure binary Se 90 In 10 glassy system. These results have been explained on the basis of some structural changes with third element Sb as an impurity in the pure binary Se 90 In 10 glassy alloy*. Keywords: Thin films, Chalcogenide glasses, Space charge limited conduction, Density of defect states 1 Introduction Chalcogenide glasses have been quite attractive due to their potential applications in active as well as passive solid-state electronics and optical devices such as; switching memory, thermal imagining, chemical, Ultra-high density phase-change storage and memory, Integrated fiber optics, infrared photo detectors, photoreceptor and photovoltaic 1-10 .The electrical properties of amorphous Se based chalcogenide glasses exhibit large Fermi level shift and large photo voltaic effects 11,12 . The structure of amorphous Se and the effect of alloying indium (In) into Se have been carried out by researchers and reported in the literature 13,14 . These studies indicate that when In is incorporated to amorphous Se it is dissolved in the Se chains to satisfy its coordination requirements and form a cross- link structure, which retards the crystallization probability and enhance thermal stability. Besides, it is also found that the optical band gap of Se-In is of the order of 1.3 eV at 300 K, which is close to the theoretical optimum value for solar energy conversion 15 . Thus, glassy Se-In alloys have drawn great attention because of their potential applications in solar cells 16,17 . In spite of that, these alloys are still found to have low glass transition and crystallization temperature and hence, their physical properties may deteriorate with temperature and time during use. The effect of incorporation of third element in binary chalcogenide glassy alloys has always been an interesting problem. In Ge-Se and Se-In systems, some metallic additives have been found 18-23 to change conduction from p-type to n-type and hence, these binary systems are of great importance. The addition of third element, like Sb to Se-In alloys will expand the glass forming region and create compositional and configurationally disorder, which offer ample possibilities for controlling the desired thermal properties by means of changing the chemical composition 24 . The addition of Sb to Se-In system is expected to modify the material properties to make it more suitable for device application. It has been found that the structure of the glass 25 is considerably modified by the addition of Sb. As high field effects are most readily observed in chalcogenide materials because of their low conductivity (Joule heating is negligibly small at moderate temperatures) and have been studied by various groups working in this field 26-29 . The results of these researchers have been interpreted in terms of heating effect, space charge limited conduction (SCLC) and high field conduction due to the Poole- Frenkel effect. This indicates that the interpretation of the high field data is highly intriguing in these materials and much has to be done in this field. ___________ *Work supported by Department of Science and Technology (DST), New Delhi