Atomic structure and composition of the P-rich InP(001) surfaces

The microscopic structure of the P-rich (2 x 1)-like surfaces of InP(001) i s investigated by sort X-ray photoemission spectroscopy (SXPS) and scanning tunneling microscopy (STM). The samples were grown by metal organic vapor phase epitaxy (MOVPE) and then transferred under ultra high vacuum (UHV) co nditions to UHV analysis chambers. STM images show a P-rich as-grown surfac e after transfer and another less P-rich surface after prolonged annealing at 350 degrees C. The In4d emission line is not affected by the change in s urface reconstruction and shows a small surface component shifted by 0.48 e V towards higher binding energies. The line shape of the P2p core level, on the other hand, changes: On the as-grown surface, one surface component wh ich is shifted by 0.98 eV towards higher binding energies is found after tr ansfer, whereas two surface components shifted to higher and lower binding energies, respectively, appear after annealing at 350 degrees C. These resu lts are consistent with the structure models derived from STM for the diffe rent P-rich (2 x 1)-like surfaces. (C) 2000 Elsevier Science B.V. All right s reserved.