X-ray absorption and photoelectron spectroscopy investigation of binary Nickelphosphides

Crystalline NiP3, Ni5P4, Ni12P5, and Ni3P have been investigated by means of X-ray Photoelectron (XPS): X-ray excited Auger electron (XAES), and X-ray Absorption Spectroscopy (XAS) at the P K-edge. The phosphorus Auger parameters alpha' derived from the XPS/XAES measurements have larger values compared with elemental red and black phosphorus which gives the spectroscopic evidence for the metallic character of the Ni-phosphides. A correlation between them and the average P --> Ni coordination number reflects the higher electronic polarizibility of neighbored Ni compared with P atoms. The observed negative chemical shifts of the first inflection points of the P K-XAS spectra compared with elemental phosphorus point on a negative partial charge of the phosphorus atoms in these crystals. (C) 1997 Elsevier Science B.V.