Gallium phosphate thin solid films: structural and chemical determination of the oxygen surroundings by XANES and XPS

Amorphous dielectric gallium phosphate thin films of various chemical compositions were deposited on silicon substrates by the 'pyrosol' process. This paper reports the results of a structural study of these deposits before and after thermal annealing. Oxygen K-edge X-ray Absorption Near Edge Structures (XANES) measurements and oxygen 1s (O 1s) core-level X-ray Photoelectron Spectroscopy (WS) data collection were carried out in order to probe the oxygen surroundings and chemical states. In P-rich thin films, the O atoms are dicoordinated, with the coexistence of Ga-O-P and P-O-P bridges. In Ga-enriched deposits, the oxygen atoms are mainly dicoordinated to gallium atoms. The annealed P-rich films are composed of dicoordinated oxygen atoms forming only Ga-O-P linkages, while in the annealed Ga-rich deposits, the O atoms present a mixed surroundings constituted of di, tri and tetracoordinated oxygen atoms. (C) 1998 Elsevier Science S.A. All rights reserved.