Switching Effects in Evaporated Arsenic Sulphide Films

Abstract

Thin films of arsenic trisulphide were evaporated from amorphous arsenic sulphide bulk material, by high vacuum evaporation technique on to glass substrates at room temperature. Electrodes used to measure the current (I) voltage (V) characteristics were made of aluminium. The current-voltage characteristics obey the relation

I=aVⁿ

where a is a constant. Value of n ranges from 1 at relatively lower voltages to higher values for higher voltages. At threshold voltage (V_th), the material switches on to a highly conducting state. This change in structure is regenerative in contrast to the nonregenerative breakdown for an insulator; because on increasing the voltage in the on-state, current increases linearly obeying the Ohm's Law and after a critical current value, it suddenly switches back to the initial off-state condition. The threshold voltage (V_th) decreases with increasing the temperature from 300°K to 440°K.

The non-linearity in I—V characteristics in the off-state condition corresponds to different types of conduction mechanisms, viz. Schottky emission, Poole-Frenkel emission, space-charge limited currents or tunnelling in potential barriers. All these phenomena indicate the presence of localized states within the band gap.

The mechanism of electrical breakdown in these films which depends on temperature for given thickness of films and sample geometry has been discussed.

Additional information

Notes on contributors

Manisha Datta

Datta, M: Educated in Calcutta University. At present working as a Junior Research Fellow of University Grants Commission, in Physics Department, Calcutta University. Research interest in experimental Solid State Physics and X-rays.

P.N. Banerjee

Banerjee, P N: Born on July 28th, 1952. Educated in Calcutta University. At present lecturer in Physics, Surendranath College, Calcutta. Research interest in experimental study of Electronic properties of materials.

D.L. Bhattacharya

Bhattacharya, D L: Born on October 26th,. 1924. Educated in Rangoon University and Calcutta University and PhD of Maryland University USA. Head of the Department of Physics, Calcutta University since 1977. Specialisation in Experimental Solid-State Physics and Electron Microscopy.