Studies on certain vanadium pentoxide based semiconducting oxide glasses exhibiting majority charge carrier reversal phenomenon

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Vanadium Pentoxide (V2O5) based glasses form an important class of amorphous semiconductors. V2O5 based glasses are normally n-type semiconductors. The possibility of obtaining p-type semiconductors in some V2O5 based trenary glasses has been pointed out in the literature. After a careful study of the glass-forming region of known V2O5 based glassed systems coupled with the thermoelectric power (TEP) measurements, three glass systems, namely, x V2O5.20SnO.(80-x)TeO2 glasses (18<_ x<_50), x V2O5.40CaO. (60-x) P2O5 glasses (10<_x<_30) and x V2O5.40CaO.(60-x)B2O3 glasses (10<_x<_30) were identified for the present investigations. These three glass systems exhibit a reversal in the carrier type from n-type to p-type when the composition x was systematically varied. Bulk glass samples belonging to the three glass systems were prepared by melt quenching technique. The as-quenched samples were characterized using X-ray diffraction technique, TEP measurement and differential scanning calorimeter (DSC). TEP measurements revealed that the career reversal occurs near 23 mol%V2O5 in V2O5-SnO-TeO2 glasses. In V2O5-CaO-P2O5 and V2O5-CaO-B2O3 glasses, the career reversal was observed at 20 mol%V2O5.
Supervisor: A. Srinivasan