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

Abstract 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 (XPS) 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.