Thesis Defense: Callisto MacIsaac (Bent Group)
Title: "Atomic Layer Deposition (ALD): Mechanisms and Hybrid Materials for Energy Applications"
Atomic layer deposition (ALD) is a versatile tool for depositing a wide variety of materials including metals, metal oxides, and metal sulphides. The technique involves sequential self-limiting reactions to obtain atomic-level control over the thickness of the resultant thin films. This works focuses on the application of ALD to two systems with relevance to the rapidly growing clean energy market: zinc-tin-oxide (ZTO) and a new inorganic-organic material modelled on MoS2 which we named Mo-thiolate.
The ALD of ZTO, a commercially important transparent conducting oxide used in both solar cells and transistors, was explored using in situ Fourier transform infrared spectroscopy (FTIR). Ligands from the gaseous ALD precursors were found to persist on the reaction surface during the process, and substantially impact the composition and thickness of the resultant films. This was the first literature demonstration of persisting ligands for the ZTO process and its component ZnO and SnO2 processes, and offered great insight into ALD surface chemistries. Secondly, the Mo-thiolate material was synthesized to be an analogue of the 2D material MoS2, however the process incorporated organic ligands that disrupted the chemically inert basal planes that exist in MoS2. This resulted in a transparent thin film with a higher catalytic activity toward the hydrogen evolution reaction (HER) then a flat MoS2 thin film. The films were found to be stable in HER conditions for at least 30 minutes.