Photo-thermal deflection and electrical switching studies on Ge-Te-I chalcohalide glasses

Measurements on thermal diffusivity (alpha) and electrical switching studies have been undertaken on bulk, melt-quenched Ge22Te78-xIx (3 <= x <= 10) chalcohalide glasses. The thermal diffusivity values of Ge22Te78-xIx glasses lie in the range 0.09-0.02 cm(2) s(-1), and are found to decrease with increase in iodine content. The variation of a with composition has been understood on the basis of fragmentation of the Ge-Te network with the addition of iodine. The composition x = 5 ((r(c)) over bar = 2.39), at which a cusp is seen in the composition dependence of thermal diffusivity, has been identified to be the inverse rigidity percolation threshold of the Ge22Te78-xIx system at which the network connectivity is completely lost. Further, Ge22Te78-xIx glasses are found to exhibit memory-type electrical switching. At lower iodine concentrations, a decrease is seen in switching voltages with an increase in iodine content, in comparison with the switching voltage of the Ge22Te78 base glass. The observed initial decrease in the switching voltages with the addition of iodine is due to the decrease in network connectivity. An increase is seen in switching voltages of Ge22Te78-xIx glasses at higher iodine contents, which suggests the domination of the metallicity factor of the additive atoms on the switching voltages at higher iodine proportions. It is also interesting to note that the composition dependence of the threshold voltages shows a slope change at x = 5, the inverse rigidity percolation threshold of the Ge22Te78-xIx system.