Nanostructured heterogeneous catalysts are designed to increase activity and selectivity of reactions. Currently catalysts are designed using calcination and impregnation methods, which result in poor uniformity due to a lack of control of the size, structure and composition and lead to unwanted by-products in a catalytic reaction. In order to improve on catalyst design and control of the growth at the nano-and meso-scale, it is vital that surface chemical approaches are understood, where tailored functionality is incorporated on the atomic scale. Atomic layer deposition (ALD) is a vapor deposition technique that utilizes surface chemical reactions to grow metal oxides from inorganic precursors one atomic layer at a time. Atomic control is achieved though self-limiting surface reactions, where the surface functional groups initiate the first step in the deposition process. We investigate how surface chemical reaction sites result in selective deposition of aluminum oxide (Al2O3) using ALD. The highly ordered pyrolytic graphite (HOPG) surface is used as a model support for Al2O3 growth. The HOPG surface is a multilayered graphene surface that possesses interfacial ordering of sp2 carbon atoms making their terraces relatively inert towards adsorption of weakly binding molecules, albeit their defects remain highly reactive. We show how different treatments of the HOPG surface result in different growth of surface morphologies of Al2O3. The surfaces are analyzed using X-ray photoelectron spectroscopy, Fourier transform-infrared spectroscopy, Raman spectroscopy and mapping, scanning electron microscopy and atomic force microscopy. Our studies suggest that the growth of Al2O3 on functionalized HOPG using ALD is achieved by controlling the morphology of functional sites. The knowledge learned using this proof-of-concept method provides a fundamental understanding of surface functionalization leading to metal oxide growth using bottom-up approaches.

Investigation of selective growth of ALD alumina on functionalized HOPG surfaces

256th National Meeting (2018)

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