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A nitridation process of a diamond surface with nitrogen radical exposure far from the radio-frequency plasma for the stabilization of a negatively charged nitrogen-vacancy (NV−) centers near the surface is presented. At a nitrogen coverage of as high as 0.9 monolayers, high average Rabi contrasts of 0.40 ± 0.06 and 0.46 ± 0.03 have been obtained for single NV− centers formed by shallow nitrogen implantation with acceleration voltages of 1 and 2 keV, respectively. This indicates that nitrogen termination by a radical exposure process produces an electric charge state suitable for single NV− centers near the surface compared with the states obtained for alternatively terminated surfaces. [ABSTRACT FROM AUTHOR]

Total photoyield spectroscopy (TPYS) measurement is applied to boron (B)-doped polycrystalline diamond, which shows an extremely low cathode fall voltage (Vc) in glow discharge operation. The B-doped diamond film grown on a molybdenum (Mo) substrate shows Vc of about 43 V after hydrogenation with a small amount of hydrogen added to argon (Ar + 0.03% H2). This Vc value is almost 1/3 that of the Mo substrate without diamond. The TPY spectrum of the diamond after hydrogenation in microwave hydrogen plasma shows obvious onset at 4.5 eV, which is below the band-gap energy of diamond (5.47 eV). This is attributed to the negative electron affinity (NEA), which results in an electron affinity of −1.0 eV. Vc and TPY spectra are also measured for acid treatment condition and Mo. From these experiments, the low Vc values of B-doped polycrystalline diamond depending on the surface treatment correlate to the difference between electron affinities derived from the TPYS measurements. [ABSTRACT FROM AUTHOR]

Electron spectro-microscopic methods were applied as direct methods of determining the Schottky barrier heights (SBHs) and their spatial distribution for Au- and Ag-Schottky junctions fabricated on an acid-treated oxygen-terminated diamond (001) substrate. Metal layers were formed with two ranges of thickness (3–5 nm for thin layers and 13–100 nm for thick layers) for both Au- and Ag-Schottky junctions. Leading X-ray photoelectron spectroscopy (XPS) core-level peaks of either Au 4f7/2 or Ag 3d5/2 for the metal layers and C 1s for diamond were used as measures of the SBH. For the thick-metal samples, spatially resolved XPS measurements were performed over most of the sample surface. It was found that there is a variation in SBH on the order of 0.1 eV for the large (“high barrier”) SBH values and that there are several places where the SBHs were rather small (“low barrier” junction). For the thin-metal samples, less variations in SBH were observed. The average SBH of “high barrier” junctions for the thick-metal samples appeared to be slightly (0.1 eV order) larger than that for the thin-metal samples. XPS images of leading metal core levels tuned for the “high barrier” and “low barrier” SBHs were observed. For the thick-Ag Schottky sample, the resulting Ag 3d5/2 XPS images clearly showed the locations of defective Schottly junctions. It is suggested that the SBHs determined for the thin-metal samples are the average SBHs on the measured surface and that the SBHs determined for the thick-metal samples are the highest SBHs within the measured µm-size metal islands. The presently determined SBHs were compared with previously reported SBHs and reasonable agreement was found. Photoemission electron microscopy (PEEM) images were observed for the thick-Ag Schottky sample and the “low barrier” islands were identified. The methodologies of XPS, XPS imaging, and PEEM used for the thick-metal samples can be applied to any Schottky junction on diamond. [ABSTRACT FROM AUTHOR]