Effect of Seed Size, Suspension Recycling and Substrate Pre-Treatment on the CVD Growth of Diamond Coatings

Abstract

CVD growth of uniform conformal polycrystalline diamond (PCD) coatings over complex three dimensional structures is very important material processing technique. It has been found that the nucleation and subsequent growth period is very critical for successful development of CVD diamond based technologies. There are many methods of enhancing diamond nucleation on foreign substrates-ultrasonic treatment with diamond seed suspension being the best among them. A combination of ultrasonic seeding (US) technique with prior treatment (PT) of the substrate under CVD diamond growth conditions for brief period of time, has found to be very effective in enhancing the diamond nucleation during CVD growth-together they are known as NNP. But successive usage of the same seeding suspension up to ten cycles deteriorates the seeding efficiency. 6 th seeding cycle onwards the silicon substrates are barely get covered by diamond crystallites. Five different diamond micron grits were used for seeding the silicon substrates and it is observed that US with the sub-micron particles (0.25 µm) is very effective in efficient nucleation of PCD on Si substrates. PT of the substrate somewhat negates the effect of successive use of the same seeding slurry but it is best to avoid recycling of the same seeding suspension using micron size diamond grits.

Some Aspects of Diamonds in Scientific Research and High Technology

“…Nucleation density determines the faster grain coalescence phenomenon during chemical vapour deposition. It has been observed that DND seeds are much superior in enhancing nucleation of diamond than conventional micron size grits for seeding diamond nuclei on the foreign substrates [119]. The particle size of seeds is thus important in determining nucleation efficiency.…”

Seed Dibbling Method for the Growth of High-Quality Diamond on GaN

“…The diamond seeding step before the growth can also affect the quality of the diamond film, grain size, thermal conductivity, and TBRs. , A high seeding density on the substrate, using diamond nanoseeds with densities above 10 11 cm –2 , can initiate a fast growth and diamond film coalescence, which could minimize the GaN decomposition under hydrogen plasma environment and thus improve the adhesion . A recent study has experimented with mixed-sized diamond seeding using microseeds and nanoseeds to grow CVD diamond films on GaN and AlN .…”