Precursor synthesis, chemical vapour deposition and thermoelectric measurements of group (14) and (15) Chalcogenide thin films

Abstract

The overarching aims of the project were to use a single source precursor (SSP) approach to the chemical vapour deposition (CVD) of thin films of materials of interest for thermoelectrics and to develop this further to enhance the performance of these deposits. This approach would allow for exploration of the materials and the potential for optimisation whilst considering sustainability and enhancements possible through nanostructuring, charge carrier concentration, crystal structure modulation, morphology and composition. In this work these factors have been controlled through adjustments to deposition temperature, precursor load, precursor design and mixture. With a focus on materials that are of interest for their thermoelectric properties, SnSe was selected as the initial target due to its exciting reported potential for thermoelectric applications.1 Previous single source precursors developed within the group had been utilised to deposit SnSe,2 however, these depositions produced only a small amount of discontinuous SnSe, the depositions occurred at very high temperatures and produced other phases. Thus, an alternative single source precursor capable of producing phase pure, continuous SnSe thin films, preferably at lower temperatures, was investigated initially. Once a feasible SSP had been identified for SnSe depositions, this type of precursor was extended to explore the deposition of other group 14 chalcogenide materials and then adapted for the deposition of Bi and Sb chalcogenide thin films. This thesis will cover the low pressure chemical vapour deposition of tin and germanium chalcogenides, silicon telluride, bismuth and antimony chalcogenides as well as a number of ternary solid solution systems, the selective deposition of SnTe3 and the wafer scale CVD of SnSe using a commercial rig. The importance of these materials for thermoelectric applications or other semiconductor functionalities will also be discussed along with measured electrical and thermoelectric properties and potential avenues for their optimisation.

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ORCID for Gillian Reid: orcid.org/0000-0001-5349-3468

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