Nucleation and growth behavior of epitaxial Pb(Zr,Ti)O-3/MgO(100) observedby atomic force microscopy

Nucleation and growth of epitaxially grown lead zirconium titanate (PZT) th in films on as-cleaved MgO(100) substrate were studied with X-ray diffracti on and atomic force microscopy using a tapping mode. The films were grown b y MOCVD at different deposition times from 10 to 1800 s at 650 degrees C. A t the initial stage of the film deposition, the growth of layer-like PZT th in film was observed up to thickness of 1.0-1.2 nm, which corresponds to 5- 6 monolayers (ML) of PZT. The chemical composition of initial layer was sto ichiometric PZT. Over the thickness, formation of island structure was obse rved at thickness of around 2 nm. Then coalescence of three dimensional nuc lei to form monodispersed grain size distribution via bimodal distribution and grain growth proceeds not only perpendicular but also horizontal to the substrate with increasing deposition time. This indicates that the growth mechanism coincides with Stranski-Krastanov (SK) growth mode. It was also c larified that the grain size distribution corresponds to the root mean squa re (rms) roughness on the preparation of thin film. The critical thickness of PZT thin film on MgO(100) substrate was 1.0-1.2 nm in good agreement wit h other reported epitaxial grown thin films. (C) 1999 Elsevier Science S.A. All rights reserved.