An XPS study of the nucleation and growth behavior of an epitaxial Pb(Zr,Ti)O 3/MgO(100) thin film prepared by MOCVD

Abstract

The chemical states and the composition of the surface of the epitaxially-grown lead zirconium titanate (PZT) thin films, prepared by MOCVD on an as-cleaved MgO(100) substrate, were studied by X-ray photoelectron spectroscopy (XPS). At our deposition rate (4.3 nm/min), lateral growth occurred at 20-s depositions, and three-dimensional growth occurred after 30-s depositions. Between the 10 and 40-s depositions, the XPS spectra of Pb (4f) had shoulders at 141 and 136 eV, which strongly suggested that metal Pb co-exists with PZT in the lateral growth region. The binding energy of C (1s) was almost constant, irrespective of the deposition time (deposition mode). However, the binding energies of Pb (4f), Zr (3d), Ti (2p), and O (1s) showed a tendency that binding energy in the lateral growth mode was slightly higher than in the three-dimensional growth mode. The surface atomic ratio Zr/(Zr+Ti) was constant between 10 and 1800 s; on the other hand, the surface atomic ratio Pb/(Pb+Zr+Ti) was almost stoichiometric at the initial stage of deposition, increased with deposition time, and turned out to be constant above 100 s, with a value of Pb/(Pb+Zr+Ti)=0.6.