Metallorganic chemical vapor deposition of lead oxide and lead titanate

Abstract

The purpose of this study was two-fold: firstly, the MOCVD deposition behavior of Pb(thd)2 was studied in detail and a one-dimensional kinetic model was proposed to successfully predict the effect of processing conditions on the deposition rate profile for PbO. Assuming the surface reaction is the rate-limiting step in the process, the effective activation energy for the process, Ea, was found to be 82 kJ/mol while the preexponential rate constant was found to be 33 g/cm2/min (0.15 moVcm2/min). The process was found to consistently produce a combination of the high temperature, orthorhombic modification of lead monoxide with randomly oriented plates of tetragonal lead monoxide. TEM electron diffraction was used to investigate the crystal orientation of the individual plates which was found to be in the plane normal to the <201> zone.

Secondly, the deposition behavior of PbTi03 and the resulting film structure and properties were investigated. Pb(thd)2 was used in conjunction with titanium ethoxide (Ti(OEt)4) as a titanium source. Stoichiometric lead titanate films which were found to be smooth, specular and transparent, and well-adhered were deposited on a variety of substrates by careful control of the experimental conditions. Film structure, composition, and thickness were studied and correlated to changes in various experimental parameters. Additionally, a high temperature regime at which the film stoichiometry is relatively insensitive to experimental conditions was found to occur. The effects of post-annealing on the as-deposited films including compositional changes, morphological changes and crystal structure was also studied. Some problems were obtained with film peeling on the ruthenium oxide (Ru0₂)-coated substrates which could be alleviated somewhat by the use of (100) oriented silicon wafer rather than (111) oriented silicon; a possible mechanism to explain this behavior is also suggested. Optical properties were obtained using UV -VISNIR transmission and reflectance spectroscopy; the ferroelectric hysteresis behavior of the films was observed using standard R T -66 A test equipment.