AES AND EELS ANALYSIS OF THE INTERACTION BETWEEN PHOSPHORUS AND METALLIC INDIUM

Phosphorus, mainly in the form of P2, has been evaporated on a InP(100 ) sample in order to compensate P vacancies and to remove metallic In clusters from the surface. These defects were induced by argon ion bom bardment or vacuum annealing during the ''in situ'' cleaning procedure of the substrate. The damaged InP surface, characterized by EELS and AES, may be considered as a (In, InP) two-phases system in which the c ontent and the distribution of metallic indium is dependent on the exp erimental parameters used in the treatments. Phosphorus evaporation on this sample at room temperature induces a typical change of the loss spectra. The intensity of the lines characteristic of metallic indium (surface and volume plasmons at 8,6 eV and 11,5 eV, respectively) are decreased while the volume plasmon of indium phosphide at 15 eV is enh anced. A saturation of the interaction between phosphorus and the (In, InP) system occurs after metallic indium clusters are changed to indi um phosphide. The transformation of metallic In to covalent InP bonds is supported by Auger line shape analysis of the In-MNN and P-LMM spec tra. The removal of the stoichiometry defects of the InP substrate lea ds to a surface more stable (against heat treatments and electron stim ulated oxydation) than the initial disordered one. For comparison, a p ure polycrystalline metallic In sample has been investigated simultane ously to the InP substrate, and subjected to phosphorus evaporation un der similar conditions. Such a treatment results in the formation on t he In metal surface of a thin InP layer of a thickness larger than the probed depth (about 2 nm).