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

The microscopic structure of the P-rich 2=1.-like surfaces of InP 001.is investigated by soft 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.conditions to UHV analysis chambers. STM images show a P-rich as-grown surface after transfer and another less P-rich surface after prolonged annealing at 3508C. The In4d emission line is not affected by the change in surface reconstruction and shows a small surface component shifted by 0.48 eV 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 which is shifted by 0.98 eV towards higher binding energies is found after transfer, whereas two surface components shifted to higher and lower binding energies, respectively, appear after annealing at 3508C. These results are consistent with the structure models derived from STM for the different P-rich 2=1.-like surfaces. q2000 Elsevier Science B.V. All rights reserved.