Investigation of Thin Al2O3 Films Grown by Atomic Layer Deposition (ALD) on TiO2 substrate

Abstract

Abstract Atomic layer deposition (ALD) is a feasible method for thin film deposition which allows the formation of a thin film of metal oxides on the various substrates. The film deposition is carried out in a vacuum reactor using chemical precursors (typically gases) which can react with the surface in a self-limiting manner. Each cycle in the ALD process can, in theory, form a monolayer of the desired metal oxide. Because the monolayer is deposited in each cycle, the thickness of the resulting film is related to the number of ALD cycles. In this thesis, the deposition of thin film Al2O¬3 on TiO2 nanoparticles by ALD was investigated. The main goal was to investigate whether Al2O¬3 can coat the inside of the pores of a porous TiO2 substrates or not. To obtain the answer, the chemical composition of the sample surface was studied using X-ray photoelectron spectroscopy (XPS). The initial X-ray photoelectron survey scan spectrum for each individual sample was recorded, followed by the high-resolution scans for the elements of interest. Moreover, the morphology of substrate after Al2O3 deposition by ALD was also examined using Scanning Electron Microscopy (SEM). In one experiment, four samples of Al2O3 on TiO2 substrate were prepared. Three of these samples were mixed, redissolved in ethanol, and redeposited on to a new silicon wafer. This was labelled as the redeposited sample. While the other one sample was labelled as the reference sample. The relative intensity of Al/Ti from all samples were calculated. It was found that Al2O3 intensity decreases. This result suggests that the diffusion of Al2O3 to porous structure of the substrate did occur.