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

我们使用表面敏感方法对ALD生长的基本和功能特性进行了系统的原位研究。我们在不同温度下保持有规则阶梯状表面的衬底上使用ALD，并通过扫描显微镜表征表面扩散的发生和强度。我们确定了作为衬底温度和平均平台宽度的函数的ALD成核位的分布，给出了扩散的定量估计，以了解其在ALD中的作用。我们将在规则表面上获得的知识应用到多晶衬底上，以便找到在复杂表面上沉积平板薄膜的实验条件。我们将标准的ALD方法应用于具有不同氧化状态和晶体结构的氧化物衬底上，并用同步辐射光电子能谱和吸收光谱对薄膜的生长进行了表征。衬底化学和结构根据它们对ALD前体的反应性来改变生长和界面特征。通过选择合适的支撑材料和ALD参数，我们确定了氧化物衬底的氧化态和晶体结构在调整界面、衬底和ALD膜功能方面所起的不同作用。这些研究将在现场进行，使用具有极高表面敏感性的表征方法。这种组合在国际上是独一无二的，已经证明可以澄清ALD的意外特性。

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.