Positron annihilation induced Auger electron spectroscopy (PAES) study of the structure of Si/H/Ge(100) interfaces

Positron annihilation induced Auger electron spectroscopy (PAES), which makes use of low energy positrons to excite Auger transitions by annihilation of core electrons, was applied to the study of the effect of adsorbed atomic hydrogen on the stability of Si films grown on a Ge(100) substrate. Previous work has shown that PAES has a high degree of selectivity for the topmost atomic layer due to the trapping of positrons in an image potential well just outside the surface before annihilation. The concentration of Si and Ge atoms on the surface layer were monitored by measuring PAES intensities of the Si LVV and Ge MVV peaks after deposition of Si on Ge(100) with and without the prior adsorption of H on the substrate. The PAES results indicated that when 8 ML of Si was deposited on Ge(100) after introducing 5000 L H2, the surface consisted almost exclusively of Si atoms. In the absence of H, segregation of Ge atoms to the surface was observed even after deposition of 8 ML of Si at room temperature.