Interaction of nanometer-sized gold nanocrystals with rutile (110) surface steps revealed at atomic resolution

We show that progress in atomic resolution Z-contrast imaging now enables a detailed understanding of nanocrystal (NC) interaction with surface steps. The interaction is measured based on the shape, orientation, strain and interfacial energy of Au NCs on surface steps of rutile (TiO₂) (110) surfaces with a small miscut. Au NCs with the approximate Au(111)_{[- 110]} || TiO₂(110)_[001] epitaxial relationship are selected for study. Results show that the presence of surface steps induces a small rotation in the NCs in an amount less than the surface miscut angle. Atomic displacements measured from atomic resolution images show significant strain near the surface steps inside Au NCs. The shape of Au NCs on low miscut surfaces, however, is approximately similar. From this, an analysis of the average NC shape is performed using the modified Wulff-Kaishew theorem. Compared to Au NCs on flat surfaces, the measurements show a large height/width ratio, lowered interfacial energy and increased triple line energy for NCs observed on surface steps.