Effect of zinc incorporation on the density of defect states in a-$Se_{85} Te_{15}$ glassy alloy

Abstract

Present work incorporates the study of d.c. conductivity measurements at high electric fields in vacuum evaporated thin films of $Se_{85-x} Te_{15}Zn_x$ (x = 0, 2, 4, 6 and 10) glassy alloys. Current-Voltage (I-V) characteristics have been measured at various fixed temperatures. In these samples, at low electric fields, ohmic behavior is observed. However, at high electric fields (E ∼ $10^4$ V/cm), non ohmic behavior is observed. An analysis of the experimental data confirms the presence of space charge limited conduction (SCLC) in 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 DOS is increasing with increase in concentration of Zn in pure binary $Se_{85} Te_{15}$ glassy system. The results obtained have been explained on the basis of some structural changes with third element Zn as an impurity in thepure binary $Se_{85} Te_{15}$ glassy alloy and have been correlated with the electronegativity difference between the elements used in making the aforesaid glassy systems.