In Situ Studies of Tetrahedrally Bonded Thin Film Nucleation, Surfaces, and Interfaces

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The aim of the proposed research program is to obtain a fundamental understanding of the structure and properties of tetrahedrally coordinated thin film surfaces and interfaces and their relationship to the physics and chemistry of deposition. Progress in these aspects of thin film science has been very slow owing to the complexity of the plasma processes for deposition and the relative lack of in situ probes for studying nucleation, and reactions at surfaces and interfaces, particularly in adverse high pressure plasma environments. In situ spectroscopic ellipsometry (SE) is a monolayer-sensitive, non-perturbative technique which will be applied to these problems. A unique optical multichannel analyzer-based ellipsometry system in place now permits collection of dielectric function spectra from 1.1 eV to 4.5 eV with a minimum time resolution of less than one second. This allows spectra to be taken at every Angstrom during the growth of these films. A second instrument will also be developed under this proposal. The materials to be studied are hydrogenated and hydrogen-free amorphous carbon and silicon as well as microcrystalline diamond. The preparation capabilities will include plasma enhanced chemical vapor deposition (CVD), heated filament enhanced CVD, remote plasma CVD, all from CH4 or SiH4. Physical vapor deposition techniques include evaporation, with and without ion assist, dc planar magnetron sputtering, and ion beam sputtering. The studies will concentrate on the nucleation and interface structure of microcrystalline diamond thin films and the response of their surfaces to well- characterized inert and reactive ion beams. Similar experiments will be used to probe the nucleation, surface reactivity, and bonding for the Si-based films. These experiments will be used to identify the physical factors which control film bonding and morphology.