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Surface graphitization as a result of Joule heating by a field-emission (FE) current is revealed for needlelike diamond nanotips. The apex temperature and electrical resistance of the diamond needles during FE were measured by electron spectroscopy. Transmission electron microscopy indicated that the diamond structure in the near-surface layer was transformed into well-ordered graphene layers after FE with currents of up to 30 μA. The resulting structure can be viewed as a multi-walled carbon nanotube (MWCNT) having a diamond core. Thus, the observed FE behavior exhibited by the graphitized diamond needles is qualitatively similar to that of MWCNTs. On the other hand, due to its outstanding thermal conductivity, the diamond core ensures an efficient Joule heat dissipation, which provides better emission stability and higher currents, up to at least 225 μA. It makes these graphitized diamond needles promising candidates for high-brightness point electron sources required for various applications, e.g., in electron microscopy or scanning electron lithography. [ABSTRACT FROM AUTHOR]

To transform a monocrystalline diamond into monocrystalline graphite, the exposure of an ultrafast laser to a (111) diamond face was investigated for the first time. The single pulse of the third harmonic of a Ti:sapphire laser (100 fs, 266 nm) was used to produce graphitized inclusions embedded in a (111) diamond substrate. Three different regimes of (111) diamond graphitization are discussed in this paper. Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy were used to investigate the graphitized material, which was found to resemble highly oriented graphite at certain laser fluencies. The proposed approach to the problem of perfect local diamond graphitization is an important step toward creating all-carbon composite systems consisting of conductive and dielectric phases. [ABSTRACT FROM AUTHOR]

This paper reports the analysis of the intensity of diamond line in the Raman spectra of laser modified layers with different thickness on a diamond surface. Since the diamond line passing from substrate through the absorbing layer of moderate thickness can be registered, the thickness of local area is estimated from its micro‐Raman spectra. The comparison between Raman scattering and direct observation of the graphitized layer by transmission electron microscopy shows that Raman spectroscopy can be used as an alternative non‐destructive method for measuring a moderate thickness of graphitized layers. [ABSTRACT FROM AUTHOR]