IN-SITU OXIDATION OF ULTRATHIN LAYERS OF GE ON SI(001) - EVIDENCE FOR BONDING PARTNER EXCHANGE

Ultra-thin layers of Ge grown on Si(001) surface are oxidized in situ and investigated using XPS, AES, MEIS, AFM and TEM. The samples used are Ge layer formed by deposition at room temperature (RT) and SiGe mixed layer formed by deposition at 550 degrees C. Oxidation of the RT-grown layer forms GeO on the surface and on annealing the surface to 360 degrees C, oxygen changes the bonding partner and forms SiO2, thereby reducing GeO to elemental Ge. In the SiGe mixed layer, after oxidation, SiO2 and a small amount of GeO are formed. On annealing, a similar reaction takes place on this surface also, forming SiO2 as the final product on the surface. Air oxidation of the RT-deposited sample forms Ge suboxides and GeO2 on the surface. GeO is reduced selectively by annealing at 360 degrees C in vacuum. On the other hand, by rinsing the sample in warm water, GeO2 is removed selectively.