Pt/PbZrxTi1-xO3 interfacial reaction and Schottky barrier formation studied by x-ray photoelectron spectroscopy: Effect of H-2 and O-2 annealing

The Pt/PbZrxTi1-xO3 (PZT) interfacial reaction caused by low- temperature ( 320 degrees C) annealing and resulting change in the surface Fermi level po sition (Schottky barrier height) has been studied by using in vacuo x-ray p hotoelectron spectroscopy (XPS). A thin (2 nm) Pt layer was deposited on a polycrystalline PZT film and annealed in 0.5-Torr H-2 and O-2 in a chamber connected to the XPS chamber. For the PZT samples annealed prior to Pt depo sition, a small amount of metallic Pb was produced after the Pt deposition. The annealing also moved the surface Fermi level (E-F) at the Schottky int erface toward the conduction band minimum (E-C) of PZT by 0.4 eV, as eviden ced by the band-bending shift of the PZT core levels. Excess metallic state s appeared in the valence-band spectra of an annealed bare PZT surface. The re was no appreciable annealing-atmosphere dependence in the amount of meta llic Pb produced and surface E-F position at the PT/PZT interface. However, a clear annealing-atmosphere dependence was observed for the samples annea led after the Pt deposition. The H-2 annealing enhanced the production of m etallic Pb, whereas the O-2 annealing suppressed the metallic Pb formation. The H-2 annealing moved the surface E-F toward E-C by 1.0 eV,whereas the O -2 annealing caused no measurable change in the surface E-F position. The c atalytic effect of Pt during the annealing was postulated to explain the ob served annealing-atmosphere dependence. (C) 1999 American Institute of Phys ics. [S0021-8979(99)01011-7].