Studies on electrical switching behavior and optical band gap of amorphous Ge-Te-Sn thin films

Amorphous thin film Ge ₁₅Te _85-x Sn _x (1≤x≤5) and Ge ₁₇Te _83-x Sn _x (1≤x≤4) switching devices have been deposited in sandwich geometry using a flash evaporation technique, with aluminum as the top and bottom electrodes. Electrical switching studies indicate that these films exhibit memory type electrical switching behavior. The switching fields for both the series of samples have been found to decrease with increase in Sn concentration, which confirms that the metallicity effect on switching fields/voltages, commonly seen in bulk glassy chalcogenides, is valid in amorphous chalcogenide thin films also. In addition, there is no manifestation of rigidity percolation in the composition dependence of switching fields of Ge ₁₅Te _85-x Sn _x and Ge ₁₇Te _83-x Sn _x amorphous thin film samples. The observed composition dependence of switching fields of amorphous Ge ₁₅Te _85-x Sn _x and Ge ₁₇Te _83-x Sn _x thin films has been understood on the basis of Chemically Ordered Network model. The optical band gap for these samples, calculated from the absorption spectra, has been found to exhibit a decreasing trend with increasing Sn concentration, which is consistent with the composition dependence of switching fields.