(0001) QUARTZ SURFACE IMPERFECTIONS

Monocrystalline (0001) quartz surfaces may present two kinds of imperf ections point defects (surface oxygen vacancies) and tridimensional di sorder (superficial amorphization). The point defects are studied than ks to Reflection Electron Energy Loss Spectroscopy experiments, which show that electronic transitions (5.1 and 7.2 eV) associated with surf ace oxygen vacancies appear in the gap of alpha-quartz under ion or el ectron bombardment and 900-degrees-C vacuum heating. The defects respo nsible for these structures are located in the first nm under the surf ace. X-ray Absorption Near Edge experiments (XANES) at the O K-edge sh ow that the 900-degrees-C vacuum heating leads moreover to the destruc tion of the surface crystallinity (almost-equal-to 5 nm), as proved by the modification of the multiple scattering structures.