Electrical properties of amorphous Se 70Ge 30−xM x system, where M represents silver, cadmium or lead

Abstract

Current–voltage characteristics and DC electrical conductivity were measured for Se 70Ge 30− x M x ( x = 0 , 5 and M=Ag, Cd or Pb) thin film samples as a function of temperature and thickness. DC conductivity increases with temperature and with the addition of Ag, Cd or Pb, while it decreases with increasing film thickness. The observed increase in conductivity with Pb is higher than that with Cd, which in turn is higher than that with Ag. The obtained results showed that the conduction activation energy has two values Δ E σ 1 and Δ E σ 2 indicating the presence of two different conduction mechanisms through the investigated range of temperature (308–453 K). Current–voltage curves of the investigated samples are typical for a memory switch. The mean value of the threshold voltage V th ¯ increases with film thickness and decreases with increasing temperature in the range (308–403 K) and with the addition of Ag, Cd or Pb. The obtained mean value (0.471) of the ratio ε / Δ E σ 2 (where ε is the threshold voltage activation energy) for the investigated compositions agrees with the value of 0.5 obtained theoretically on the basis of an electrothermal model. Moreover, the obtained values of Δ T breakdown for most of the investigated compositions are in the same order with those obtained before. Therefore the switching phenomenon in the investigated compositions can be explained according to the electrothermal model.