Fundamental and functional properties of ultra-thin oxide films grown by atomic layer deposition (ALD) studied in-situ by means of surface sensitive techniques

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We perform a systematic in-situ study of fundamental and functional properties of ALD growth using surface sensitive methods. We use ALD on substrates with regularly stepped surfaces held at various temperatures and characterize the occurrence and strength of surface diffusion by means of scanning microscopy. We determine the distribution of ALD nucleating sites as a function of substrate temperature and average terrace width, giving a quantitative estimation of diffusion for understanding its role in ALD. We apply the knowledge gained on regular surfaces to polycrystalline substrates in order to find the experimental conditions for depositing flat films also on complex surfaces. We apply standard ALD procedures to oxide substrates with different oxidation state and crystalline structure and characterise the film growth by means of Synchrotron radiation photoemission and absorption spectroscopy. Substrate chemistry and structure modify growth and interface features depending on their reactivity towards the ALD precursor. We determine the distinct roles played by oxidation state and crystalline structure of the oxide substrates to tailor interface, substrate and ALD film functionalities upon choice of the appropriate supporting material and ALD parameters. These studies will be done in-situ, using characterization methods with extreme surface sensitivity. Such a combination, unique at international level, has already proven to clarify unexpected properties of ALD.