Surface Functionalization of III–V Nanowires

The physical and chemical properties of semiconductor nanowires are significantly influenced by their surface structure and morphology. This can be understood in that surfaces make out a much larger part of the total structure as compared to macroscale objects. An immediate consequence is that the lack of surface control can result in poor performance and reproducibility of any nanowire device. It is clear that bad performance is problematic, but it must be stressed that without performance reproducibility across millions of nanowires they can never become a useful real technology. This is indeed why many promising nanostructures and materials lost interest of both the scientific and commercial communities. However, surface control also can be used to strongly enhance nanowire performance and even introduce new functionality. As a result, surface functionalization is a key issue for nanowire science and technology. In this chapter, we describe in detail how standard surface science techniques such as Scanning Tunneling Microscopy (STM) and X-ray Photoemission Spectroscopy (XPS) can be modified for effective studies of 1D nanowires despite that they have been originally invented only for large and flat 2D surfaces. We go on to give a number of examples on how these techniques have revealed the precise structure–function relationship in particular of III–V semiconductor nanowires and their surfaces. We further discuss, how this can be used to control the structure and chemistry of the wires down to the atomic scale enabling new functionality for (opto)electronics, sensors, and many other device types. While we focus on III–V nanowires, the examples and techniques put forward should be applicable to many other material systems and types of nanostructures.