In-situ growth of oriented PbTiO3 thin films by low temperature metalorganic chemical vapor deposition

摘要

Oriented PbTiO3 thin films were successfully grown on (200)-oriented Pt/SiO2/Si by metalorganic chemical vapor deposition at low temperature range from 350°C to 400°C, using β-diketonate complex of Pb(tmhd)2 and titanium isopropoxide as source precursors. Dependences of orientation and formation of crystalline PbTiO3 phase on Pb/Ti ratio and substrate temperature was investigated. Crystalline phases and preferred orientations were determined by X-ray diffraction technique, and surface morphology was identified with scanning electron microscopy. As the deposition temperature was raised from 350°C to 400°C at two fixed Pb/Ti ratios of 3.3 and 5.0, structures of PbTiO3w3 films transformed from amorphous to polycrystalline and preferred orientation changed from random to [100] parallel to the surface. Similar results were also observed in the films deposited at 400°C with the increase of Pb/Ti ratio from 1.1 to 5.0. As the Pb/Ti ratio increased, the dielectric constant and current density increased due to crystallization of the PbTiO3 films. It is found that the control of excess Pb precursor amount through Pb/Ti ratio change is the key process parameter for the formation of crystalline PbTiO3 phase in the low temperature MOCVD process.