Trimer adatom structure of phosphorus on Ge(111) - art. no. 165320

The surface structures of phosphorus on a Ge(111)c(2 x 8) surface have been investigated by scanning tunneling microscopy (STM), low-energy electron d iffraction, and Auger electron spectroscopy. Phosphorus adatoms are stable on the Ge(111) surface up to similar to 350 degreesC, where desorption and/ or diffusion into the bulk sets in. The P adatoms cluster into small island s and form a local (root3 x root3)R30 degrees structure. The stable bonding configuration of phosphorus on Ge(lll) between room temperature and simila r to 260 degreesC is the so-called T-4 trimer geometry, where the P adatoms form triangular trimer units above second-layer Ge atoms, thus saturating all the Ge surface dangling bonds in the local (root3 x root3)R30 degrees a rray. However, only poor long-range order is obtained. The P-3 trimers repl ace the Ce adatoms of the c(2 x 8) reconstruction as revealed in atomically resolved STM images. The P trimer structure on Ge(lll) is discussed in rel ation to the substitutional adsorption geometry of P on Si(111), and it is argued that the Ge(111)(root3 x root3)R30 degrees -P-3 structure is the res ult of the larger tensile stress on the Ge surface and the weaker Ge-P bond strength as compared to the Si case.