UHV μ-electron beam evaluation of the CVD diamond particles grown on Si (001)

The electronic and structural properties of diamond particles chemical vapor deposition (CVD)-grown on Si(001) surfaces were studied using a scanning probe ♂-electron beam with SEM, RHEED, secondary-electron spectroscopy (SES) and Auger-electron spectroscopy in ultra-high-vacuum (UHV) conditions. The CVD grown diamond particles studied were made with a source gas of either CO/H₂ (sample A) or CH₄/H₂ (sample B) on Si(001). The UHV-SEM images showed that sample A was composed of diamond particles with well-determined low-index surfaces while those for sample B with poorly determined surfaces. ♂-RHEED patterns from diamond single-crystallites for sample A showed well-developed Kikuchi-bands together with surface spots indicating a good order of diamond framework near the surface. The diamond crystallites of sample A showed varieties of SES spectra and only a small fraction of them had negative electron affinity (NEA) although no differences are found in RHEED. The SES spectra for sample B showed that essentially all the diamond particles are NEA. It is found that the Fermi-level is located at ∼ 1.0 eV above the valence band maximum for NEA diamond particles and ∼ 1.5 eV for PEA ones. The change in electron affinity and the origin of surface conductive layers present on as-grown CVD diamonds are discussed in terms of the Fermi-level positions found presently.