Microcrystalline diamond

Catledge, S., Baker, R, Tarvin, J., and Vohra, Y., Multilayer nanocrystalline/microcrystalline diamond films studied by laser reflectance interferometry, in Diamond and Related Mater., 9 (8), 1512-1517 (2000). 

It is well known that nitrogen can be easily incorporated in diamond, and usually, it must be very eareful of the air leak in the CVD chamber to prevent nitrogen contamination of diamond films. It is also known that addition of too much nitrogen to the source gas resulted in microcrystalline diamond films rather than well-faceted films. However, Koidl s group found [90] using a NIRIM-type reactor that an addition of small amount of N2 gas to the source gas of c=l-2%CH4/H2 resulted in pronounced (100)-textured films, while the film became microcrystalline without N2 addition. More specifically, an addition of 40-200 ppm of N2 to the... 

The soultrananocrystalline diamond (UNCD) is a special 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 microcrystalline diamond seed did not show any increase in size after hydro-thermal treatment, but particles of <50nm size, which typically show a regular... 

The names for these two film types arise from their nominal crystallite size and morphology. Figure 5 shows scanning electron microscopy (SEM) images of the two types of boron-doped diamond thin film deposited on Si. High quality microcrystalline diamond films are deposited from CH4/H2 source gas mixtures with volumetric ratios of 0.3 to 1.0%,... 

FIG. 9. Background cyclic voltammetric i-E curves for (a) glassy carbon, (b) a moderately boron-doped microcrystalline diamond film electrode, and (c) a heavily boron-doped microcrystalline diamond film electrode in 0.1 M HCIO4. Electrode area = 0.2 cm. Scan rate = 0.1 V/s. 

Ru(NH3)6, 0.1 mM IrClg, and 0.05 mM methyl viologen (MV ) at a boron-doped microcrystalline diamond thin-film electrode. Scan rate = 0.1 V/s. Electrolyte = 1 M KCl. 

Cyclic Voltammetric and Heterogeneous Electron Transfer Rate Constant Data for Four Aqueous-Based Redox Systems at Boron-Doped Microcrystalline Diamond Thin-Film Electrodes... 

FIG. 12. Cyclic voltammetric i-E curves for a boron-doped microcrystalline diamond electrode in 1 mM ascorbic acid + 0.1 M HCIO4 before, after anodic polarization at different potentials, and after rehydrogenation in a hydrogen plasma. 

Figure 18 shows typical cyclic voltammetric i-E curves for 1.0 mM (A) cadaverine (CAD), (B) putrescine (PUT), (C) spermidine (SPMD), and (D) 0.8 mM spermine (SPM) in borax buffer pH 11 (BBpHll) at a microcrystalline diamond thin film deposited from a 0.5% CH4/H2 ratio and 10 ppm B2H6. Similarly shaped curves were observed for several other amines and polyamines (e.g., methylamine, ethylamine, propylamine, ethylenediamine, 1,3-diaminopropane, 1,6-hexamethylenediamine, and... 

FIG. 19. Cyclic voltammetric i-E curves for 1 mM cadaverine in 0.01 M carbonate bulfer/0.1 M NaQ04, pH 10.6, at a microcrystalline diamond film deposited from a 0.67% CH4/H2 ratio. (A) As deposited and (B) acid-washed and rehydrogenated diamond film. Scan rate = 10 mV/s. (Reprinted with permission from Anal. Chem., 71,1188 (1999). Copyright (1999) American Chemical Society.) (From Ref. 39.)... 

Figure 23B presents IR transmission spectra for (5) an optically pure and mechanically polished white diamond disc, (6) an undoped and polished (both sides) Si substrate, and (7 and 8) moderately and heavily boron-doped microcrystalline diamond thin films deposited on the undoped Si. The white diamond is relatively free of structural defects and chemical impurities. There is reduced transparency between 2500 and 1500 cm due to the two-phonon absorption. Diamond films with more... 

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