Electronic and optical band gap of Ge–Te–Sn nanostructure

Abstract

Amorphous thin film Ge15Te85−xSnx (1 ≤ x ≤ 5) and Ge17Te83−xSnx (1 x 4) switching devices have been deposited in sandwich geometry using a flash evaporation technique, with aluminum as the top and bot- tom 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 con- centration, 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 rigid- ity percolation in the composition dependence of switching fields of Ge15Te85−xSnx and Ge17Te83−xSnx amorphous thin film samples. The observed composition dependence of switching fields of amorphous Ge15Te85−xSnx and Ge17Te83−xSnx 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 in- creasing Sn concentration, which is consistent with the com- position dependence of switching fields.