Electron spectroscopy on boron nitride thin films: Comparison of near-surface to bulk electronic properties

Combining spectroscopic methods probing both occupied as well as unoccupied electronic states, the surface electronic structure of es situ prepared bo ron-nitride films is analyzed and compared to experimental and theoretical bulk-electronic properties taken from the literature. X-ray photoelectron s pectroscopy is applied to probe the core-level and valence-band electronic states, electron-energy-loss spectroscopy in the reflection geometry to inv estigate conduction band states as well as excitations like plasmons and co re excitons. For films with hexagonal structure, the results from the near- surface region are found to reflect both the ground state and the many-body properties of the bulk material. Cubic boron nitride films in all cases ex hibit a hexagonal-like top layer with a thickness of about 0.9 nm. Low-ener gy ion bombardment at room temperature is found to significantly increase t he amount of disorder in both types of films, leading to the transformation of the cubic phase into a hexagonal-like material. [S0163-1829(99)02607-7] .