Performing atomic layer deposition (ALD) of metal oxides at pressures around 0.01 mbar slows the half reactions of the process to allow in situ and real-time probing of changes in the surface electronic structure using ambient pressure X-ray photoelectron spectroscopy (APXPS). By monitoring the ALD process as it occurs, new details on the mechanisms of interface formation and thin film growth can be obtained. The deposition of HfO2 on InAs and the deposition of TiO2 on rutile titania from transition metal coordination complexes and water were studied with APXPS. Predictable, cyclic chemical shifts of ligand and substrate ionizations are seen in the growth of both films. However, the kinetics of the film growth differs for the two systems. Upon exposure to the titania surface, the titanium precursor reacts straightaway and gradually proceeds to completion. In contrast, the halfnium precursor does not interact with the surface immediately. Once an activation barrier is surpassed, the reaction occurs instantaneously. During the interface formation between the HfO2 and InAs, the self-cleaning of the native arsenic oxide is observed through the disappearance of a component in the As 3d ionization. By understanding the reactivity of different precursors, the ALD process can be more easily optimized in applications that require thin films of metal oxides such as metal-oxide-semiconductor devices and catalytic surfaces.

Real-time studies of the atomic layer deposition of metal oxides using ambient pressure X-ray photoelectron spectroscopy

247th National Meeting (2014)

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