Improvements in CVD/CVI processes for optimizing nanocrystalline diamond growth into porous silicon

This paper reports a novel procedure to infiltrate nanocrystalline diamond films (NCD) on porous silicon (PS) substrate. The NCD/PS films resulted in a composite material, with great potential for electrochemical application, mainly due to its high active surface area. The Hot Filament Chemical Vapor Deposition reactor was changed to Hot Filament Chemical Vapor Infiltration reactor in order to grow NCD films infiltrated into deep holes of PS substrate. This procedure allowed the infiltration of the reacting gases into the porous structure where the nucleation takes place, followed by the coalescence and film formation at pore bottoms and walls. In this configuration an additional entrance of CH4 was located next to the PS substrate using two distinct positions called “underneath” and “above”, with the use of the additional flow accurately underneath or above of the samples. In general, the combination of these two configurations with additional carbon sources provided NCD film infiltration in PS substrate with success with only 60 min of growing time. Particularly, the films obtained from the positions called “above” presented the best morphology, with high quality and crystallinity, confirmed from its scanning electron microscopy, Raman scattering spectroscopy and high resolution X-ray diffraction spectra, respectively.