Browsing by Author "Li, C. C."

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    Processing of PbTiO3 thin films. I. in situ investigation of formation kinetics
    Li, C. C.; Desu, Seshu B. (American Institute of Physics, 1996-01-01)
    A novel in situ stress measurement technique to study the formation kinetics of multicomponent oxide thin films was developed and was applied to PbTiO3. Single phase PbTiO3 thin films were formed from the reaction between films in the deposited PbO/TiO2 multilayer. The film. stoichiometry was accurately controlled by depositing individual layers with the required thickness. The development of film stresses associated with the formation of the product layer at the PbO/TiO2 interface of the multilayers was used to monitor the growth rate of the PbTiO3 layer. It was found that growth of the PbTiO3 phase obeyed the parabolic law, and the effective activation energy was estimated to be 108 kJ/mole. It is believed that the mechanism of this reaction was dominated by grain boundary diffusion of the participating cations. (C) 1996 American Vacuum Society.
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    Processing of PbTiO3 thin films. II. in situ investigation of stress relaxation
    Li, C. C.; Desu, Seshu B. (American Institute of Physics, 1996-01-01)
    Stress relaxation in PbTiO3 films was investigated by the in situ stress measurement technique. A simple viscous flow model was successfully used to interpret the kinetics and behavior of stress relaxation of PbTiO3 thin films. The activation energy responsible for stress relaxation was estimated to be 190 kJ/mole, which was accounted for by the lattice diffusion of vacancies. A Nabarro-Herring creep model was successfully employed to correlate the relationships among the viscosity, lattice diffusion coefficient, and grain size of the PbTiO3 films, and an estimate of the lattice diffusion coefficient of vacancy motion during relaxation was obtained. Also, the observed time required for complete relaxation was found to be in accord with theoretical values. Hillock formation resulting from grain boundary sliding is believed to contribute to stress relaxation in its early stage. Thereafter, grain growth resulting from lattice diffusion is believed to play a major role in the stress relaxation. (C) 1996 American Vacuum Society.
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    Processing of PbTiO3 thin films. III. Effects of ion bombardment
    Li, C. C.; Desu, Seshu B. (American Institute of Physics, 1996-01-01)
    The effects of ion bombardment on multicomponent oxides, such as PbTiO3, and multilayer systems have been extensively studied by an in situ stress measurement technique. Energetic ion bombardment was found to accelerate PbTiO3 formation. Both the annealing temperature and the time needed for completion of the reaction were reduced. The apparent activation energy responsible for stress relaxation was found to be 310 kJ/mole for ion-assisted deposition (IAD) films, which is 120 kJ/mole higher than that for non-IAD films. This was attributed to stress reduction in PbTiO3 thin films resulting from ion bombardment. In addition, effects of ion bombardment on the stress of as-deposited multilayers, on the stress development in multilayers during annealing, and on the structure-property-processing interrelationships were also investigated. (C) 1996 American Vacuum Society.