In this study, we employed various surface modification techniques to improve the dispersion characteristics of NDPs in methanol solution, aiming at the diamond nucleation enhancement step in a typical CVD diamond growth process.

It is well known that the significant impurities from nondiamond carbon and metal existing in postsynthesized carbon soot include NDPs and, however, lead to serious aggregation phenomena of typical ND particles. It should be noted here that the size of particle used for spin-coating procedure also influences roughness of the diamond films, resulting in demand of a highly dispersed aqueous suspension of diamond particles with uniform and ultrafine particle size.Р”В¬ommercial detonation NDPs with round shape are usually used for nucleation enhancement step in CVD diamond growth. Among these, the method of spin-coating with diamond slurry in air at room temperature is inexpensive, environment friendly, and relatively simple thus it is appropriate for the growth of large-area diamond film, reduces the production cost, and is suitable for the commercial applications. Till now, the enhancement of the diamond nucleation density for nondiamond substrate can be carried out by various methods including spin-coating with a diamond slurry, plasma precarburization, scratching with Al 2O 3 or diamond powders, ultrasonicating with mixture of nanometal and nanodiamond particles (NDPs), and bias-enhance nucleation. In a typical diamond film grown by CVD techniques, the surface roughness is directly related to the diamond nucleation enhancement which is also known as РІР‚СљpretreatmentРІР‚Сњ procedure. Obviously, high surface roughness may hinder the performance of the diamond-based devices such as MEMS, biosensor, and p-n junction-based device. The diamond grains and grain boundaries have significant effects on not only the electrical properties, but also the surface roughness of the diamond films. The CVD-deposited diamond film normally consists of diamond grains and grain boundaries containing impurities as well as nondiamond carbon phase.

High quality undoped CVD diamond films with n- and p-type characteristics have been successfully manufactured by the most common techniques including microwave plasma-enhanced chemical vapour deposition (MPECVD) and hot filament chemical vapour deposition (HFCVD). Also, due to other important features including transparency over a wide spectral range, good thermal stability, and wear resistance, the films have been considered as promising candidates to replace silicon and metal in high performance devices which operate in harsh environments. Since chemical vapour deposition (CVD) diamond films possess many outstanding properties of diamond with low dimensional structure, they have increasingly attracted interests in the area of nanomanufacturing including semiconductor, optics, biomedical, and biosensor engineering. These results indeed open up a prospect of nanocrystalline diamond films in solar cell applications. The nanocrystalline diamond films deposited by microwave plasma jet chemical vapour deposition exhibited extremely fine grain and high smooth surfaces (~6.4РІР‚вЂ°nmРІР‚вЂ°rms) on the whole film. The results of both Fourier transform infrared spectroscopy and dynamic light scattering measurements demonstrated that plasma treated diamond nanoparticles possessed polar surface functional groups and attained high dispersion in methanol. The seeding of silicon substrate was then carried out with an optimized spin-coating method. Hydrogen plasma, thermal, and surfactant treatment techniques were employed to improve the dispersion characteristics of detonation nanodiamond particles in aqueous media. Therefore, this paper was aimed at the surface modification of the NDPs to enhance the diamond nucleation for the growth of nanocrystalline diamond films which could be used in photovoltaic applications. The formation of agglomerates in the suspension of NDPs, however, may have adverse impact on the initial growth period. The seedings of the substrate with a suspension of nanodiamond particles (NDPs) were widely used as nucleation seeds to enhance the growth of nanostructured diamond films.

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