HETEROEPITAXIAL NUCLEATION OF DIAMOND ON NICKEL

Highly oriented diamond has been grown on (100) nickel substrates by t he hot filament chemical vapor deposition method. Epitaxial nuclei wer e obtained by a diamond powder seeding and high temperature annealing process. Since the timing of the process was crucial for the achieveme nt of a high degree of orientation and high density of diamond nuclei, a real-time, in-situ laser reflectometry system was developed to moni tor changes in surface morphology observed during the high temperature annealing stage. Characteristic features observed in the intensities of reflected and scattered light were interpreted by comparison with s canning electron micrographs of the samples quenched at sequential sta ges of the process. It was concluded that the scattered light signal c an be effectively used as a process steering parameter, Using this tec hnique, oriented nucleation and growth of diamond on Ni was reproducib ly achieved. Auger spectroscopy showed that up to 6 at% of carbon was dissolved in the nickel surface layer. The investigation of interfacia l microstructures and phases involved by transmission electron microsc opy revealed the formation of Ni4C already in the early stages of nucl eation. This phase was manifested as coherent precipitates and is beli eved to have been the precursor for diamond nucleation. Perfectly epit axial diamond was grown by this process. The epitaxial relationship wa s determined by cross-sectional transmission electron microscopy and s elected area diffraction analysis. (C) 1998 Elsevier Science S.A.