Structure property relationa in AI Te and As Se

Abstract

Chalcogenide glasses are semiconducting in nature and find in wide a range of newlineapplications. These glasses are being explored for electrical memories due to their newlinehuge contrast in electrical resistivity between the amorphous and crystalline states. newlineThe broad objective of this work is to prepare metal-doped chalcogenide glasses, newlinestudy their thermal and electrical properties along with local structural changes as a newlinefunction of metal atom concentration. The aim is to finally arrive at a model to newlineunderstand the structure-property relations in metal-doped chalcogenide glasses. Bulk newlineAl-Te, As-Se and Al-X-Te (X = As, Ge, Sb and Si) glass samples with different newlinecompositions have been undertaken for this work. The thesis contains seven newlinechapters, as follows: newlineThe first chapter of the thesis provides a brief introduction about glasses, newlineglass transition phenomenon, glass forming ability, etc. Different types of newlineamorphous solid preparation methods have been outlined. The phenomenon of newlineelectrical switching, its mechanism and applications have been presented along newlinewith a brief overview of phase change memory and their applications. The second newlinechapter has information about specific experimental tools employed in this work. newlineA brief introduction on the melt quenching method has been followed with the newlinedescriptions of various characterisation techniques used. newlineThe third chapter deals with electrical switching and thermal properties of newlineAl23Te77 chalcogenide glass system. It has been shown that the structural network newlineof Al-Te glass has been cross-linked by the presence of higher coordinated Al atoms. newlineThe structural reorganisation becomes difficult due to the increased network newlineconnectivity, which favours threshold type switching. newlineThe fourth chapter has the extended study of another Al-Te sample - newlineAl20Te80 glass with different preparation conditions. It is an attempt to find the newlineorigin of 5- fold coordinated Al and its influence on electrical switching. The newlinediscussion has also been centred around the correlation between structure, thermal