The Atomic-Scale Characterization of Defects on Cleaved Vanadium and Molybdenum Oxide Surfaces Using Stm

Abstract

AbstractScanning tunneling microscopy (STM) was used to determine the structure of cleaved, single crystal surfaces of V205, V6013, Mo18052, and Mo8023. Constant current images were recorded in ultrahigh vacuum and in air. By imaging well-defined surfaces that exhibit structural and chemical similarities, and comparing the observations to the known bulk structures, it is possible to establish a reliable interpretation for the contrast in the STM images. A comparison of images from the V6013(001) and the V205(001) surfaces clearly shows that the surface V coordination polyhedra that are capped by vanadyl 0 can be distinguished from those that are not. This allows vacancies in the vanadyl 0 position to be identified on cleaved V205(001) surfaces. Mo18052(100) and Mo8023(010) provide models for two different characteristic types of surface/crystallographic shear (CS) plane intersections. The shear in Mo8023 lies in the (010) surface plane and creates dark contrast along the [001]. The CS planes in Mo18052, on the other hand, have components of shear both in and normal to the (100) surface plane and create white contrast parallel to [010]. These standards for contrast identification can be used to identify defects on inhomogeneous surfaces.