• Hjort, Martin

Abstract

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

Topics

• morphology
• surface
• x-ray photoelectron spectroscopy
• semiconductor
• Hydrogen
• electron microscopy
• scanning tunneling microscopy