Pure Tb as well as TbSi1.7/Si(100) were oxidized at 600-degrees-C for
30 min at atmospheric pressure. Auger, XPS and XRD spectra of the samp
les were measured before and after oxidation. The XRD results show tha
t pure Th oxidizes to form TbO1.81 while the oxide layer of the oxidiz
ed TbSi1.7 consists of Tb2SiO5. During sputtering of the Tb2SiO5 layer
, Auger spectra show that Th and not Si is oxidized, while the XPS spe
ctra show that Th as well as Si are oxidized as expected from the XRD
results.