Diamond coating of porous silicon

Diamond coatings on porous silicon (PS) samples have been obtained by the h ot-filament chemical vapor deposition(CVD) technique. We focused our attent ion on the coating morphology, showing experimentally that high quality dia mond coatings may be produced with the PS sample kept at 710 degrees C. The deposited patterns consist of polycrystalline grains with a plane interfac e with the PS layer. At 790 degrees C, the quality of the coating is improv ed but the PS layer becomes damaged, and at 650 degrees C the coating consi sts of diamond-like carbon particles. Besides the temperature, other factor s such as the porosity, roughness and chemical activity of the PS layer des erve attention. We observed that one of the limiting factors of the deposit ion process was the high nucleation time. Two nucleation mechanisms are inv olved in the growth process. The first nucleation mechanism occurs on the t op of the sharp PS features, subsequently to the nucleation a superficial f ilm, and then a second nucleation mechanism occurs over this surface, which allows the growth process to continue. We also observed the presence of a blue-shift in the luminescence spectra following the coating.