A comprehensive study of microwave (MW) activated CH 4 /H 2 /Ar plasmas used for diamond chemical vapor deposition is reported, focusing particularly on the effects of gross variations in the H 2 /Ar ratio in the input gas mixture (from H 2 /Ar mole fraction ratios of > 10:1, through to $1:99). Absolute column densities of C 2 (a) and CH(X) radicals and of H(n ¼ 2) atoms have been determined by cavity ringdown spectroscopy, as functions of height (z) above a substrate and of process conditions (CH 4 , H 2 , and Ar input mole fractions, total pressure, p, and input microwave power, P). Optical emission spectroscopy has also been used to explore the relative densities of electronically excited H atoms, and CH, C 2 , and C 3 radicals, as functions of these same process conditions. These experimental data are complemented by extensive 2D (r, z) modeling of the plasma chemistry, which provides a quantitative rationale for all of the experimental observations. Progressive replacement of H 2 by Ar (at constant p and P) leads to an expanded plasma volume. Under H 2-rich conditions, > 90% of the input MW power is absorbed through rovibrational excitation of H 2. Reducing the H 2 content (as in an Ar-rich plasma) leads to a reduction in the absorbed power density; the plasma necessarily expands in order to accommodate a given input power. The average power density in an Ar-rich plasma is much lower than that in an H 2-rich plasma operating at the same p and P. Progressive replacement of H 2 by Ar is shown also to result in an increased electron temperature, an increased [H]/[H 2 ] number density ratio, but little change in the maximum gas temperature in the plasma core (which is consistently $3000 K). Given the increased [H]/[H 2 ] ratio, the fast H-shifting (C y H x þ H $ C y H xÀ1 þ H 2 ; y ¼ 1À3) reactions ensure that the core of Ar-rich plasma contains much higher relative abundances of "product" species like C atoms, and C 2, and C 3 radicals. The effects of Ar dilution on the absorbed power dissipation pathways and the various species concentrations just above the growing diamond film are also investigated and discussed. V

With nanotextured surfaces and interfaces increasingly being encountered in technological and biomedical applications, there is a need for a better understanding of frictional properties involving such surfaces. Here we report friction measurements of several nanostructured surfaces using an Atomic Force Microscope (AFM). These nanostructured surfaces provide well defined model systems on which we have tested the applicability of Amontons' laws of friction. Our results show that Amontonian behaviour is observed with each of the surfaces studied. However, no correlation has been found between measured friction and various surface roughness parameters such as average surface roughness (R(a)) and root mean squared (rms) roughness. Instead, we propose that the friction coefficient may be decomposed into two contributions, i.e., μ = μ(0) + μ(g), with the intrinsic friction coefficient μ(0) accounting for the chemical nature of the surfaces and the geometric friction coefficient μ(g) for the presence of nanotextures. We have found a possible correlation between μ(g) and the average local slope of the surface nanotextures.

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In this study, we report the production of amine functionalized nanodiamond. The amine functionalized nanodiamond forms a conformal monolayer on a negatively charged surface produced via plasma polymerization of acrylic acid. Nanodiamond terminated surfaces were studied as substrates for neuronal cell culture. NG108-15 neuroblastoma-glioma hybrid cells were successfully cultured upon amine functionalized nanodiamond coated surfaces for between 1 and 7 d. Additionally, primary dorsal root ganglion (DRG) neurons and Schwann cells isolated from Wistar rats were also successfully cultured over a period of 21 d illustrating the potential of the coating for applications in the treatment of peripheral nerve injury.

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