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Abstract: Sulfur-assisted hot-filament chemical vapor deposition (HFCVD) was employed to grow nanocrystalline diamond at low substrate temperature, ∼300 °C, on molybdenum (Mo), and ∼250 °C, on polyimide film. The polyimide films remained flexible and strong after the deposition, clearly indicating that they did not experience temperatures near or above the glass transition temperature at ∼360 °C. The relative intensity of the diamond peak in the Raman spectra increases when the substrate temperature is decreased from ∼500 to ∼300 °C, a result that is inverted with respect to HFCVD without sulfur. This behavior was employed to obtain microcrystalline diamond on Mo at ∼270 °C. Profound changes induced to the gas phase chemistry and surface reactions when a trace amount of H2S is added to the HFCVD process seem to enable these results. [Copyright &y& Elsevier]

Abstract: We have applied Density Functional Theory (DFT) within the Generalized Gradient Approximation to study the behavior of lithium impurities in the diamond lattice. It was found that, although isolated interstitial lithium atoms in tetrahedral sites have a donor state relatively close to the conduction band at 0.35 eV, their behavior is critically affected by adjacent interstitials. Lithium atoms that occupy adjacent interstitial tetrahedral sites cluster spontaneously and induce carbon–carbon bond breaking in their neighborhood. The corresponding charge distribution and electronic density of states analyses show that charge localization takes place at the carbon atoms around the lithium clusters and deeper mid-gap states are introduced in the diamond band gap. The formation energy was found to be 1.88 eV and 3.09 eV, for clusters of two and three lithium atoms, respectively, considered in this study. The calculations also indicate that Li clustering would not take place if Li ions instead of atoms were incorporated interstitially. [Copyright &y& Elsevier]

Abstract: We performed a systematic study of the bactericide and bacterial anti-adhesive properties of nanocrystalline diamond (NCD) and microcrystalline diamond (MCD) in comparison to other important industrial materials, such as copper, silver, polyethylene (Poly), and stainless steel (SS). The data show that NCD has better bactericide and bacterial anti-adhesive activity than Ag, but not as good as Cu. MCD, on the other hand, does not appear to have significant anti-bacterial activity. The superlative properties of NCD, such as mechanical hardness, resistance to oxidation and corrosion, and biological compatibility with blood and tissue, enable its use as antibacterial coating for medical implants. This is an application that cannot be achieved by Cu, which is known to be a highly effective antibacterial material but is not biocompatible. We also discuss possible underlying mechanisms to help understand the bactericide and bacterial anti-adhesive properties of the NCD surface. [Copyright &y& Elsevier]

Abstract: Spontaneously detaching self-standing diamond films were successfully fabricated using saturated hydrocarbon polymers as seeding source by hot filament chemical vapor deposition (HFCVD) technique. X-ray diffraction confirmed the crystal structure of diamond. The microcrystalline morphology of the diamond films was analyzed by atomic force microscopy (AFM) and scanning electron microscopy. Raman spectra from the front and back sides of the films show the characteristic diamond band at 1332cm−1 and no carbide layer. EELS spectra also show the signature features of diamond. The use of hydrocarbon polymers as seeding source will improve the cost-effectiveness of the fabrication of diamond wafers by simplifying the fabrication process. [Copyright &y& Elsevier]

The effects of heavy-ion radiation over the electron field emission (EFE) properties of sulfur-doped nanocomposite carbon (n-C:S) films were investigated. Two identical sets of n-C:S films were prepared in a hot-filament chemical vapor deposition system using CH4, H2 and H2S. Films with various sp3 C and sp2 C fractions were present within each set. Raman spectroscopy revealed the composite nature of the films. One set of films was submitted to a 20 krad dose of energetic Si and Fe ions (GeV/amu) at Brookhaven National Laboratory''s alternating gradient synchrotron. Films originally having poor EFE properties showed a dramatic emission enhancement as a result of irradiation, while those having good EFE properties before irradiation showed a small emission improvement upon irradiation. This improved EFE behavior is explained as due to the formation of conductive trigonal carbon nano-channels within the tetragonally-bonded carbon matrix. The diameter of these trigonal carbon nano-channels is small enough to produce large local field enhancement, and large enough to withstand the relatively large emitted current densities. A mechanism is proposed for the creation of this graphitic carbon nano-wire network within the tetragonal carbon matrix upon energetic irradiation. The results suggest that radiation-hardened cold cathodes can be fabricated using nanocomposite carbon materials that would remain stable in their EFE properties while exposed to ionizing radiation. [Copyright &y& Elsevier]