a Study of the Nucleation and Growth of Diamond on Silicon by Scanning Tunneling Microscopy and Spectroscopy.

The techniques of scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) were applied to the characterization of doped and undoped diamond deposited on silicon. These results were compared with diamond deposited on germanium and copper. After one half hour growth, the surface showed additional topography over all regions, and widely spaced faceted structures were detected which were attributed to diamond nuclei. The surface between nuclei showed increased roughness with increased deposition time. The faceted nuclei were found along the scratches. Two modes of growth were observed: a normal three-dimensional mode of growth and in some cases a two-dimensional mode of growth. It was observed that the growth of the nuclei conformed to the surface of the substrate. The subsequent development of CVD diamond films grown on silicon were also documented by scanning tunneling microscopy. The samples used were grown from 0.5 hours to 26 hours. The complete films showed small scale surface morphologies, island growth, and growth between the facets. The silicon substrate of the thickest film was etched off to create a freestanding film. The growth side of the thickest film showed similar topography to that of the thinner diamond films. The etched side showed remnants of polishing scratches that were on the silicon substrate and allowed for determination of the approximate critical nucleus size. The STS portion of the study examined the electronic properties of surfaces. A complete polycrystalline diamond film, with a thickness of several microns, showed a similar electronic structure to single crystal diamond. The electronic structures of both doped and undoped nuclei were found to be similar to that of single crystal diamond, with slight variations. The freestanding film, described above, showed that the etched and growth sides of the film had different electronic structures. The growth surface had a similar electronic structure as that of thinner polycrystalline diamond films. The etched side showed evidence of silicon carbide and graphite electronic structures, which relates to the composition of the surface prior to and during the nucleation phase of diamond growth.