Non-ohmic behavior in a-Se80−xTe20Cdx thin films

The present paper reports the d.c. conductivity measurements at high electric fields in vacuum evaporated thin films of amorphous Se80−xTe20Cdx (x = 0, 5, 10, 15) systems. Current–voltage (I–V) characteristics have been measured at various fixed temperatures. In all the samples, at low electric fields ohmic behavior is observed. However, at high electric fields (E ∼ 104 V/cm), non-ohmic behavior is observed. An analysis of the experimental data confirms the presence of space charge limited conduction (SCLC) in all 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 is calculated. It is found that the incorporation of Cd like a third element as an impurity could not change the density of defect states significantly in pure binary Se–Te glassy system.