Search

Abstract: Silicon substrates are often used to synthesize polycrystalline diamond films by microwave plasma assisted chemical vapour deposition technique (MPCVD). In the case of highly oriented diamond films, several steps are employed to carefully prepare the silicon surface (pre-treatment steps), to nucleate diamond crystals (nucleation step) and to thick the film (growth step). In this study, we characterize {100} silicon substrates and diamond released from its silicon substrate by electronic microscopies (TEM and SEM), by Atomic Force Microscopy (AFM) and by X-ray photoelectron spectroscopy (XPS), to follow the substrate transformations after each step, particularly the formation and the evolution of the silicon carbide and to characterise the diamond films grown on the carburised silicon. We show that according to the experimental conditions and the level of surface/gas contamination by carbon and silicon species, isolated islands or continuous β-SiC compound are formed over the silicon surface and can generate defects such as voids or strip structures that influence the subsequent diamond nucleation and growth. [Copyright &y& Elsevier]

Isolated diamond crystals have been deposited on silicon by the microwave plasma assisted chemical vapor deposition technique using the bias-enhanced nucleation step. The true epitaxial ratio, defined as the number of epitaxied crystals to the total crystal number before coalescence, has been calculated by high-resolution scanning electron microscopy coupled to image analysis software. This ratio is correlated to the conditions of the etching step which precedes the bias step. This investigation allows us to determine the better conditions to obtain homogeneous epitaxied deposit with an optimum epitaxial ratio in the absence of a preceding carburization step, and to propose a qualitative explanation about the effect of the etching step on the silicon substrate. [Copyright &y& Elsevier]

Highly oriented diamond (HOD) films were deposited on Si (0 0 1) substrates by the microwave plasma assisted chemical vapor deposition technique using the bias enhanced nucleation (BEN) step. The formation of HOD films is often linked to the presence of few parts per million of nitrogen which stabilizes the texture but deteriorates the chemical quality of the film. In this study, we show that carbon monoxide can be used without nitrogen addition to conserve the 〈0 0 1〉 texture and to promote the {1 0 0} facet extension on the top of the diamond film. After a nucleation step carried out by the BEN technique, and after a subsequent growth time limited to 30 min in a CH4/H2 gas mixture avoiding the coalescence step, HOD films were synthesized using CH4/H2, CO/H2 and N2/CH4/H2 gas mixtures for a growth time fixed to 10–14 h. The effect of carbon monoxide or nitrogen on the morphologies and the texture of the diamond films is discussed from the results of scanning electron microscopy and the texture measurements performed by X-ray diffraction. [Copyright &y& Elsevier]