Structural properties of mocvd-grown PbTiO₃ thin films at low temperature

Oriented PbTiO₃ thin films were successfully grown on Pt/SiO₂/Si by metalorganic chemical vapor deposition at low temperature range from 350°C to 500°C, using β-diketonate complex of Pb(tmhd)₂ and titanium isopropoxide as source precursors. Effects of Pb/Ti ratio and substrate temperature on the orientation and formation of crystalline PbTiO₃ phase were investigated. Structure of the as-grown films changed from amorphous to polycrystalline with the increase of Pb/Ti ratio from 0.8 to 5.0 at a fixed temperature of 400°C and with the raise of deposition temperature from 350°C to 400°C at fixed Pb/Ti ratios of 3.3 and 5.0. As the Pb/Ti ratio and deposition temperature increased, the leakage current density increased due to crystallization of the PbTiO₃ films. As-deposited PbTiO₃ films were analyzed by X-ray diffraction measurements, scanning electron microscopy, and micro-Raman. It is found that the control of excess Pb precursor through Pb/Ti ratio change is the key process parameter for the formation of crystalline PbTiO₃ phase in the low temperature MOCVD process.