Pt/PbZr x Ti 1−x O 3 interfacial reaction and Schottky barrier formation studied by x-ray photoelectron spectroscopy: Effect of H2 and O2 annealing

Abstract

The Pt/PbZrxTi1−xO3 (PZT) interfacial reaction caused by low-temperature (320 °C) annealing and resulting change in the surface Fermi level position (Schottky barrier height) has been studied by using in vacuo x-ray photoelectron spectroscopy (XPS). A thin (2 nm) Pt layer was deposited on a polycrystalline PZT film and annealed in 0.5-Torr H2 and O2 in a chamber connected to the XPS chamber. For the PZT samples annealed prior to Pt deposition, a small amount of metallic Pb was produced after the Pt deposition. The annealing also moved the surface Fermi level (EF) at the Schottky interface toward the conduction band minimum (EC) of PZT by 0.4 eV, as evidenced by the band-bending shift of the PZT core levels. Excess metallic states appeared in the valence-band spectra of an annealed bare PZT surface. There was no appreciable annealing-atmosphere dependence in the amount of metallic Pb produced and surface EF position at the PT/PZT interface. However, a clear annealing-atmosphere dependence was observed for the samples annealed after the Pt deposition. The H2 annealing enhanced the production of metallic Pb, whereas the O2 annealing suppressed the metallic Pb formation. The H2 annealing moved the surface EF toward EC by 1.0 eV, whereas the O2 annealing caused no measurable change in the surface EF position. The catalytic effect of Pt during the annealing was postulated to explain the observed annealing-atmosphere dependence.