Low temperature growth of oxide thin films by metalorganic chemical vapor deposition

Full text: Thin films of ferroelectric / dielectric materials of PbTiO3, Pb(Zr,Ti)O3(PZT), BaTiO3, and TiO2-x were prepared by metalorganic chemical vapor deposition (MOCVD) method on various substrates of SrTiO3, fused silica glass, p-Si, p-InSb, n-InP, p-GaAs, indium tin oxide-coated soda lime glass, Pt/Ti/SiO2/Si, RuO2/SiO2/Si and Pt/RuO2/Si substrates. Low temperature growth at substrate temperature (Ts) of 500 deg C via in-situ MOCVD process was carried out to study structural and electrical properties of the oxide thin films. The PbTiO3 and PZT films grown on Pt/Ti/SiO2/Si and fused silica glass substrates at Ts > 500 deg C usually showed polycrystalline behavior. However, the PbTiO3 films grown at Ts = 430 deg C indicated partial crystallization behavior having circular-shaped aggregations of microcrystalline phases (d= ∼10nm) which were randomly embedded in amorphous matrix phase. Although epitaxial growth of the BaTiO3 and PbTiO3 films on SrTiO3 substrates at Ts>500 deg C was possible, the films on semiconductor substrates showed amorphous or local epitaxy at near interface due to lattice misfit conditions. Growth of highly textured TiO2-x thin films having rutile phase was possible on InP(100) substrate at Ts ∼ 350 deg C. TEM studies for interface of TiO2-x/InP and TiO2-x/GaAs indicated that lattice mismatches between substrate and thin films may be one of main parameters to determine the formation of single phase of the TiO2-x at low deposition temperature