New strategy for the deposition of metals by CVD and ALD: mechanistic and kinetic investigation for the growth of cobalt as model system

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The Bielefeld team has recently developed a hydrogen-free approach to metal-chemical vapor deposition (CVD), which uses pulsed-spray evaporation (PSE) delivery of simple and commercially available metal-organic precursors in alcohols. This approach was demonstrated to be successful for the growth of a number of transition metals that are relevant in catalytic, photonic, magnetic and electronic applications. Besides the numerous technical advantages, it has the capability to operate in the liquid-injection atomic layer deposition (LI-ALD) regime as well. Notwithstanding the simplicity of the technical realization, the growth of high-quality thin films without contaminations is dependent on the complex interplay between the precursor, the surface and the alcohol which in turn depends on a variety of parameters. Thus, to fully exploit the potential of this new approach, a thorough identification and understanding of all relevant fundamental mechanisms is essential. This goal will be achieved by an intense collaboration between the project partners with complementary expertise which allow connecting the macroscopic growth behavior with the processes on the molecular scale. Results of a detailed in-situ characterization of the chemistry and the kinetics under different process conditions will be correlated with the surface chemistry investigated under ultra-high vacuum (UHV) conditions. As a model system, the growth of Co films will be studied because of the exhibited rich chemistry observed in preliminary work. In this way, the foundations shall be laid for future upscaling and optimization of the processes towards efficient and highly selective methods for the growth of pure metallic thin films.