Conduction mechanism and defect density of states in amorphous Te15 (Se100-xBix)85 glassy alloys
The present paper reports the dc conductivity measurement up to 100 V for pallets of Te15 (Se100-xBix)85 (x=0, 1, 2, 3, 4 at %) glassy alloys in temperature range (303-343 K). The dc conductivity is calculated from the I-V characteristics curves of the pellets of bulk samples prepared by melt quenching technique. The samples obey Ohm’s law in the lower (0-25 V) voltage range whereas the behaviour in the higher (25-100 V) voltage range is non-ohmic. The experimental results for all the samples fit well with the theory of space charge limited conduction SCLC for uniform distribution of localized states in the mobility gap. The density of defect states is calculated for the glassy alloys and is found to increase with Bi content. The increase in defect density of states can be explained on basis of electro negativity difference of Bi as compared to host elements. The increase in dc conductivity is probably due to Se-Bi bond concentration in the Se-Te-Bi glasses.
Chalcogenide glasses; Space charge limited conduction; Localized states; Density of states
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