AN X-RAY-ABSORPTION FINE-STRUCTURE STUDY OF GE(001)(2X1)-S

The Ge(001)(2 x 1)-S overlayer formed by dosing clean Ge(001) with H2S at room temperature and annealing to remove H has been studied using surface extended X-ray absorption fine structure (SEXAFS) and near-edg e X-ray absorption fine structure (NEXAFS). The results indicate that the S atoms sit in bridge sites on the surface with a bond length of 2 .36 +/- 0.05 angstrom. This is consistent with the breaking of the Ge- Ge surface dimers, and is thus an example of the phenomenon of adsorba te-induced dereconstruction. Comparison is made with a previous study of this system using angle-resolved photoemission fine structure (ARPE FS) and with experimental and theoretical studies of the related Ge(00 1)(1 x 1)-S overlayer formed by dosing with S2.