Segregation of In atoms at clean and hydrogen passivated InP(100) surfaces

The InP(100) surfaces cleaned by ion bombardment and annealing (IBA) are known to be In-rich. Exposure to atomic hydrogen gives rise to an even higher In surface content. The nature of these In atoms at the clean and at the passivated surface was characterized by the techniques of ultraviolet and X-ray photoelectron spectroscopy (UPS, XPS) as well as low-energy electron diffraction (LEED), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and high-resolution electron energy-loss spectroscopy (HREELS). The heavily hydrogenated surface is dominated by metallic droplets of In. Line shape analysis can separate the contributions from these droplets and the non-metallic area in between, giving new insight into band bending at this surface. It is argued that the clean surface consists of In atoms bound in dimers. HREELS-spectra exhibit an interface plasmon at 93 meV, from which the carrier concentration can be directly determined via dielectric theory. Passivation of InP with atomic hydrogen shifts the plasmon energy to lower values. Finally, hydrogenation makes it possible to create particles from nanometer- to micrometer-size.