In situ RHEED study of epitaxial gold nanocrystals on TiO2 (1 1 0) surfaces

Abstract

We report a study of epitaxial gold nanocrystals (NCs) on rutile (TiO2 (110)) surfaces using reflection high energy electron diffraction (RHEED) and ex situ electron imaging. The NCs are determined by RHEED have almost pure (111) out-of-plane epitaxy with the twin in-plane orientation relationships of [–110] Au || [001] TiO2 and [1−10] Au || [001] TiO2. The epitaxial Au NCs are formed by thermal annealing after depositing 0.1–0.4nm nominal thick Au on TiO2. In situ RHEED monitoring shows that significant Au NC crystallization occurs at >500°C annealing temperatures for nanoparticles that are of ∼2nm in diameter. The NCs are faceted as evidenced by the shape of RHEED diffraction spots and electron imaging. The sharpness of the epitaxial Au RHEED diffraction spots with ∼0.55nm−1 FWHM allows a measurement of thermal properties of Au/TiO2, such as thermal expansion and Debye temperature of Au NCs on TiO2.