Switching phenomenon in a Se₇₀Te_30–xCd_x films

¹ Physics Department, Faculty of Education, Ain Shams University, Cairo, Egypt
² National Center for Radiation Research and Technology, Cairo, Egypt

Corresponding author: ashraf.bekheet@mailcity.com

Received: 19 April 2007
Revised: 12 July 2007
Accepted: 22 August 2007
Published online: 31 October 2007

Abstract

Amorphous Se₇₀Te_30–xCd_x (x = 0, 10) are obtained by thermal evaporation under vacuum of bulk materials on pyrographite and glass substrates. The I – V characteristic curves for the two film compositions are typical for a memory switch. They exhibited a transition from an ohmic region in the lower field followed by non-ohmic region in the high field region in the preswitching region, which has been explained by the Poole-Frenkel effect. The temperature dependence of current in the ohmic region is found to be of thermally activated process. The mean value of the threshold voltage increases linearly with increasing film thickness in the thickness range (100–491 nm), while it decreases exponentially with increasing temperature in the temperature range (293–343 K) for both compositions. The results are explained in accordance with the electrothermal model for the switching process. The effect of Cd on these parameters is also investigated.