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 \sim 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 the pure 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.

Keywords: Chalcogenide glasses, thin films, SCLC, DOS

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