ABSTRACT
In this paper, we present the first non-contact atomic force microscopy (nc-AFM) of a silicene on a silver (Ag) surface, obtained by combining non-contact atomic force microscopy and scanning tunneling microscopy (STM). STM images over large areas of silicene grown on the Ag(111) surface show both (â13 × â13)R13.9° and (4 × 4) superstructures. For the widely observed (4 × 4) structure, the observed nc-AFM image is very similar to the one recorded by STM. The structure resolved by nc-AFM is compatible with only one out of two silicon atoms being visible. This indicates unambiguously a strong buckling of the silicene honeycomb layer.
ABSTRACT
Rh-Au core-shell nanoparticles were fabricated on TiO(2)(110) surface by physical vapor deposition (PVD) of Rh followed by exposure of Au at elevated sample temperature (500 K). The morphology of the bimetallic particles was checked by scanning tunneling microscopy (STM). The chemical composition of the particles was characterized by low energy ion scattering (LEIS) method. It was shown that the "seeding + growing" method described previously for growth of monometallic particles in narrow size distribution (Berko, A. et al. J. Catal. 1999, 182, 511) can also be applied for fabrication of bimetallic nanoparticles. The large mean free path of surface diffusion of gold on the oxide support makes the accumulation of Au possible exclusively on the Rh seeds formed in the first step of the procedure. By performing careful STM and LEIS experiments, it was proven that, for appropriate Au and Rh coverages, the postdeposited Au completely and uniformly covers the Rh nanoparticles.