Ian Paul Llewellyn

TfI8: Pulsed plasma deposition of lead lanthanum zirconate titanate(PLZT) and lead lanthanum titanate(PLT)

Abstract Thin films of ferroelectric lanthanum-modified lead zirconate titanate (PLZT) and lanthanum-modified lead titanate (PLT) have been prepared using a novel high-powered pulsed plasma deposition technique. This method uses a microwave-induced intense discharge in a low pressure gas containing organometallic precursors of each of the required metal atoms, together with carbon dioxide and argon. In the discharge, the precursors dissociate to produce atoms which then recombine on the substrate to form the oxide film. Results are presented on the composition and crystal form of the films as the deposition conditions are varied. By careful control of deposition temperature, it is shown that a microcrystalline perovskite phase may be grown on a wide variety of substrate materials.

Plasma etching and deposition as a method of polishing CVD diamond

As grown, CVD diamond windows have low infra-red absorption, but are highly scattering in transmission due to the presence of crystalline facets on the material surface. Conventionally, these facets are removed by mechanical polishing techniques which are slow, not easily adapted to complex shapes, and which can lead to mechanical damage and loss of strength. In this work, an attempt has been made to use a patented plasma etching and deposition method to polish CVD diamond window material optically flat. Low pressure radio frequency (rf) discharges of a variety of plasma etchant gases (Ar, H2 CCl4, SF6, CO2) have been used to etch the diamond surface. Etch rates of 2000 angstroms/minute can be obtained using carefully optimized etch chemistries. It has been shown that plasma etching the diamond window under conditions which give a high self-induced dc bias causes preferential sputtering of the edges of microcrystallites and hence polishes the diamond surface flat. Certain plasma chemistries, notably those involving chlorine, have also been found to flatten the surface by preferentially removing the crystalline facets. By plasma depositing silicon oxide on the window material it is possible to planarize the surface prior to a plasma etch stage and then plasma etch away the silicon oxide and diamond in a subsequent etch stage so smoothing the diamond surface. The affect of these polishing methods on a variety of CVD diamond films is discussed and the limitations of the technique addressed.