Ultrananocrystalline diamond

A pure form of sp3 hybridized carbon is known as diamond and this may also be synthesized at the nanoscale via detonation processing. Depending on their sizes, these are classified as nanocrystalline diamond (10 nm 100 nm), ultrananocrystalline diamond (< 10 nm) and diamondoids (hydrogenated molecules, 1 nm-2 nm). Nanodiamond exhibits low electron mobility, high thermal conductivity and its transparency allows spectro-electrochemistry [20,21]. However, ultrananocrystalline diamond exhibits poor electron mobility, poor thermal conductivity and redox activity [21,22]. 

In order to increase the intensity and focus of electrons, a field emission source may be used. This consists of a single crystal tungsten or LaBeClOO) wire that is sharpened to a tip diameter of ca. 100 nm — 1 j,m. For crystalline tungsten, the axis is suitably aligned with respect to the optical axis of the microscope. For example, a beam with a diameter < 5 nm is possible from alignment of the filament planes perpendicular to (310) and (111). In addition to W and LaBe, a number of other materials are proposed for field emission applications, such as silicon, single-walled nanotubes,and ultrananocrystalline diamond (UNCD) or Cu/Li alloy films deposited onto sharpened tips.t ... 

The sospecial form of polycrystalline diamond films consisting of nanoscopically small individual crystallites with diameters of 3-10 nm (Figure 6.4). Owing to this fine structure, the portion of carbon atoms being part of grain boundaries is in its turn markedly increased as compared to microcrystalline diamond films, which again influences properties like the surface conductivity. 

The physical properties of diamond films largely correspond to those of the macroscopic material. The only significant differences to bulk diamond arise from surface defects and from a possible doping. The spectroscopic properties are employed to characterize the diamond films obtained, to evaluate their quality and, where applicable, to identify defects and impurities. In the following, the main attention will be directed just to those features differing from the bulk properties of diamond. Further aspects are also discussed in Section 5.4 on the physical properties of nanodiamond that shares some characteristics with the so-called ultrananocrystalline diamond in particular. 

The characterization of ultrananocrystalline diamond with its large portion of grain boundaries benefits as well from the application of Raman spectroscopy as the content of sp -material in a sample can be determined rather exactly this way. In addition to the aforementioned dependency on the excitation wavelength, the... 

Figure 6.26 Raman spectrum of an ultrananocrystalline diamond film at different excitation wavelengths ( Elsevier 2000).

Kuznetsov, V.L. and Butenko, Y.V. (2005) Nanodiamond Graphitization and Properties of Onion-like Carbon, in Synthesis, Properties and Applications of Ultrananocrystalline Diamond, NATO Science Series, vol. 192 (eds D.M. Gruen,... 

Shenderova, O.A. and Gruen, D.M. (2006) Ultrananocrystalline Diamond Synthesis, Properties, and Applications, William Andrew Inc, Norwich. 

Applications of Ultrananocrystalline Diamond, NATO Science Series,... 

Bajaj P, Akin D, Gupta A, Sherman D, Shi B, Auciello O, et al. Ultrananocrystalline diamond film as an optimal cell interface for biomedical applications. Biomed Microdevices... 

Sumant A, Grierson DS, Gerbi JE, et al Toward the ultimate tribological interface surface chemistry and nanotribology of ultrananocrystalline diamond, dvMarer 17 1039-1045,... 

Williams OA, Zimmermann T, Kubovic M, Denisenko A, Kohn E, Jackman RB, Gruen DM (2005) In Gruen DM, Shenderova OA, Vul AY (eds) Synthesis, properties and applications of ultrananocrystalline diamond. Springer, Amsterdam... 

Daulton, T.L., Nanodiamonds in the cosmos microstmctural and trapped elements isotopic data, in Synthesis, Properties and Applications of Ultrananocrystalline Diamond, Gmen, D., Shenderova, O., Vul A.Ya., eds., NATO Science Series II Mathematics, Physics and Chemistry. Springer, Dordrecht, 192, 49, 2005. 

VuT, A.Ya., Characterization and physical properties of UNCD particles, in Ultrananocrystalline Diamond. Synthesis, Properties and Applications, Gruen, D.M., Shenderova, O.A., eds., William Andrew Pubhshing, Norwich, New York, USA, 379, 2006. 

O. A. Shenderova and D. M. Gruen. Ultrananocrystalline Diamond Synthesis Properties and Applications, William Andrew Publishing, New York, 2006, p. 293. 

Matrab, T., M. M. Chehimi, J. P. Boudou, F. Benedic, J. Wang, N. N. Naguib, and J. A. Carlisle. Surface functionalization of ultrananocrystalline diamond using atom transfer radical polymerization (ATRP) initiated by electro-grafted aryldiazonium salts. Diamond Relat. Mater. 15, 2006 639-644. 

Ultrananocrystalline diamond (UNCD) thin films developed and patented at Argonne National Laboratory [35, 36] exhibit a unique nanostmcture characterized by grain sizes of 3-5 nm in diameter and 0.4 nm wide grain boundaries, which yields a combination of smooth surface, low friction, and high wear resistance [37], mechanical properties similar to single crystal diamond [38], biocompatibility and... 

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