Abstract: Atomic layer deposition (ALD) is a vapor-based thin film deposition technique that relay on the self-saturating chemisorption reaction of reactants. The most important highlight of the ALD process is the conformality of the deposits in very high aspect-ratio substrate, and the precise thickness control of the deposits. This is achieved from the self-limiting nature of the highly surface-specific reactions in ALD. Hence, an in-depth understanding on the chemisorption of the precursor molecules, its reaction with the surface groups, and with the co-reactant is paramount in the development of ALD process for future materials.

Here the different steps in the ALD of metal oxide thin film is investigated using in-vacuo X-ray photoelectron spectroscopy (XPS). Using an ALD reactor connected to a XPS through a transfer chamber, the surface process undergoing during the pulsing of each reactant/co-reactant could be monitored without any vacuum break. The surface sensitivity of the metal-amide precursor and water on a model thin film substrate is investigated using the in-vacuo XPS. The type, and density of different surface functional groups on the substrate is tuned by adjusting the deposition conditions of the thin film substrate, or by pre-treating with various plasma gas. By analyzing various parameters such as surface energy, and the type of surface functional groups, an insight into the dependency of surface characteristic towards the chemisorption and nucleation steps are revealed.