III–V Nanowire Surfaces

University dissertation from Department of Physics, Lund University

Abstract: This dissertation deals with the geometric and electronic structure of surfaces on III–V semiconductor nanowires (NWs). NWs made of InAs, GaAs, and InP have been studied using scanning tunneling microscopy/spectroscopy (STM/S), low energy electron microscopy (LEEM), photoemission electron microscopy (PEEM), and x-ray photoelectron spectroscopy (XPS). All of the mentioned techniques have been developed to study 2-dimensional samples and issues related with the adaption to 3-dimensional nanostructures are discussed, together with solutions on how to overcome them. Preparation techniques of NW samples for surface science studies, including an effective and seemingly non-destructive deoxidation routine using atomic hydrogen have been developed. Using STM/S, it has become possible to study the atomic arrangement at NW surfaces and evaluate the electronic structure with very high spatial precision. NWs have been studied showing metallic surfaces due to step induced states, Fermi level pinned surfaces, and unpinned surfaces allowing for general probing of NW properties. With the STM, it was possible to image from micrometers along individual NWs down to the atomic scale evaluating, among other things, tapering, surface morphology, and surface reconstructions. Using LEEM/PEEM as a novel tool for NW studies, it has become possible to determine electronic and geometrical properties of NWs using low energy electrons or photoelectrons. NW dopant incorporation, work function, and surface atomic arrangement were studied. In addition, XPS was used to study NW surface chemistry and interfacial chemistry for NWs covered in high-? oxides