XPS AND ISS STUDY OF NITIO3 AND PBTIO3 SUBJECTED TO LOW-ENERGY ION-BOMBARDMENT .1. INFLUENCE OF THE TYPE OF ION (AR+ AND O-2(+))

Compositional and chemical changes in PbTiO3, and NiTiO3, induced by 3.5 keV Ar+ and O-2(+) ion bombardment have been studied quantitatively by XPS and ISS. Whereas in NiTiO3 the Ti/Ni ratio determined by XPS remained practically constant, a preferential loss of lead was observed in PbTiO3 during ion bombardment In that case, Ar+ removed lead more effectively than O-2(+) ions. Argon ion bombardment induced strong chemical changes in both titanates: Ni2+ and Pb2+ species were nearly totally reduced to the metallic state, while Ti4+ species were partially reduced to Ti3+ and Ti2+ oxidation states. This reduction is more efficient in PbTiO3 than in NiTiO3. The preferential loss of lead in PbTiO3 and the removal at equivalent rates of Ti and Ni in NiTiO3 are discussed within the context of the chemical stability and physical constants of the compounds by assuming a chemically guided lattice relaxation of the bombarded targets. The possibility that solid-state reactions play a role in the control of some of the results is stressed. Other possible effects, such as agglomeration or surface enrichment, are discussed by using the ISS results.