Observations of initial growth stage of epitaxial Pb(Zr,Ti)O3 thin films on SrTiO3(100) substrate by MOCVD

The initial stage of the metalorganic chemical vapor deposition growth of epitaxial Pb(Zr,Ti)O-3 (PZT) thin films on SrTiO3(100) (STO) single-crystal substrates was observed using scanning probe microscopy (SPM). Both annealed and etched STO substrates showed flat surfaces with 100-300 nm wide terraces and atomic-layered steps. SPM observations revealed that the surface of annealed STO substrates was composed of either SrO or TiO2-terminated terraces and that etched STO substrates consisted of only the TiO2-terminated surface. PZT films showed the Volmer-Weber (V-M) and Stranski-Krastanov (S-K) growth modes on the SrO and TiO2-terminated surfaces of STO substrates, respectively. The critical thickness in the S-K mode was estimated <10 unit cells. This difference in the growth mechanism of PZT thin films on different surface terminations suggests that the surface migration of adsorbed species made an important role rather than free energies of surface and interface or lattice misfit strain. (C) 2002 Elsevier Science B.V. All rights reserved.