Amorphous Se70Te30–xCdx (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 $\bar{V}_{th}$ 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.