Characteristics of PbTiO3 thin films on Pt/Ti/SiO2/Si by continuous cooling process

Abstract

In order to introduce a new deposition process for ferroelectric thin film, the deposition temperature was continuously cooled down from 580 degrees C to 400 degrees C during the deposition which we call ''continuous cooling process (CCP)''. X-ray diffraction patterns showed that the PbTiO3 thin films deposited by the CCP and at 480 degrees C had polycrystallinity, but at substrate temperatures of 400 degrees C and 580 degrees C had poor crystallinity. Scanning electron microscopy of the CCP-deposited film surface showed larger granular-like micrograins than that of the film deposited at 480 degrees C and smaller than that of the film at 580 degrees C. While there was no other phase formation at the PbTiO3-Pt interface in the CCP-deposited film, resulting in a sharp interface, there was severe interface reaction at the PbTiO3-Pt and the Pt-Si in the film deposited at 580 degrees C, resulting in an abrupt interface. Atomic force microscopy under ambient conditions showed smoother surface of the film by the CCP than that of the films at 580 degrees C. Furthermore, the film by the CCP had higher packing density than that of the film at 480 degrees C. Besides enhancement of the structural properties, the CCP deposition appeared to have improved the electrical properties such as dielectric constant, dissipation factor, leak current density and polarization. In the case of the film by the CCP, polarization-electrical field measurement showed the saturation polarization of 27 mu C cm(-2), remanent of 14 mu C cm(-2) and coercive of 150 kV. These results indicate that the CCP in metalorganic chemical vapour deposition has a possibility for fabrication of PbTiO3 ferroelectric thin films.