Boron-doped microcrystalline

Fig. 5 SEM images of (a) a boron-doped microcrystalline and (b) a boron-doped nanocrystalline diamond thin film grown on Si.

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. 

One important electrochemical technology where diamond electrodes have made a significant impact is in the area of electroanalysis. CVD diamond offers advantages over other electrodes, especially sp carbon (e.g., glassy carbon), in terms of linear dynamic range, limit of detection, response time, response precision, and response stability. Some of the reported applications of diamond in electroanalysis are highlighted below. Unless stated otherwise, all the diamond electrodes mentioned below are boron-doped, microcrystalline thin films deposited on a conducting substrate (e.g.. Si). 

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... 

FIG. 23. Transmission spectra for different materials in the (A) UV/Vis and (B) IR regions of the electromagnetic spectrum. The electrodes in (A) are (1) a thin film of ITO on quartz, (2) a thin film of boron-doped nanocrystalline diamond on quartz, (3) a thin film of mechanically polished and boron-doped diamond on an optically pure, white diamond substrate, and (4) a free-standing, boron-doped, and mechanically polished diamond disc. The electrodes in (B) are (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. (Reprinted with permission from Interface 2003, 12, 33. Copyright (2003) The Electrochemical Society, Inc.) (From Ref. 158.)... 

Diamond OTEs are also useful for studying the electrochemical and optical properties of important biomolecules, like cytochrome c. We recently reported that boron-doped microcrystalline diamond thin film electrodes are quite responsive for horse heart cytochrome c, exhibiting a very active and stable cyclic voltammetric response without any pretreatment or surface modification [119,124]. Heterogeneous electron-transfer... 

The net result is that doped a-Si H films are not very conductive (typically 10-3-10-2 Q-1 cm-1)- The Fermi level is — 0.2 eV below the conduction band in phosphorus-doped a-Si H (Spear, 1977) and is—0.5 eV above the valance band in boron-doped a-Si H (Jan et al., 1980). Since the optical gap of undoped a-Si H is typically about 1.7 eV, the built-in potential of a-Si Hp-i-n solar cells is about 1.0 eV (Williams et al., 1979). Improving the conductivity of the doped layers should lead to larger built-in potentials and consequently higher conversion efficiencies. The conductivity can be increased significantly by forming microcrystalline-doped Si H films (Mat-suda et al., 1980), but since these films contain both amorphous and crystalline phases, there is no significant increase in the built-in potential (Carlson and Smith, 1982). 

Muna, G. W., Tasheva, N. and Swain, G. M. (2004), Electro-oxidation and amperometric detection of chlorinated phenols at boron-doped diamond electrodes A comparison of microcrystalline and nanocrystalline thin films. Environ. Sci. Technol., 38(13) 3674-3682. 

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. 2. SEM images of boron-doped (A) microcrystalline and (B) nanocrystalline diamond thin films. 

Figure 7 shows x-ray diffraction patterns for moderately boron-doped ( 10 cm ) microcrystalline and nanocrystalline diamond thin... 

FIG. 7. X-ray diffraction patterns for a boron-doped (a) microcrystalline and (b) nanocrystalline diamond thin film. 

Figure 8 shows visible-Raman spectra for moderately boron-doped ( — 10 cm ) microcrystalline and nanocrystalline diamond thin films. The spectrum for the microcrystalline film consists of the one-phonon diamond line centered at 1333 cm The line width (FWHM) is ca. 10 cm and, to a first approximation, is inversely related to the phonon lifetime [123,130]. The line position is negligibly shifted from that for a reference... 

Cyclic voltammetric measurements were made using well-characterized microcrystalline, boron-doped diamond thin-film electrodes to test the material s responsiveness for ferrocene as a function of scan rate, solvent. 

Figure 8.5 Electron micrograph images of different types of boron-doped diamond (BDD) electrodes showing (A) microcrystalline flat BDD film, (B) a CNT/BDD teepee matrix, (C) a CNT/BDD ridged/honeycomb surface, and (D) higher magnification view of the film in (C). (Reproduced from ref. 37 with the permission of the American Chemical Society.)...

Haymond, S., Babcock, G.T. and Swain, G.M. (2003) Electron transfer kinetics of ferrocene at microcrystalline boron-doped diamond electrodes effect of solvent and electrolyte. Electroanalysis, 15,249. 

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