Synthesis Of Nano-diamond Film By MW-PECVD

Due to excellent properties, the highly oriented nanocrystal diamond has become a hot topic in material, physical and chemical district because of great potential for fabrication of the next generation of ultralow molecular sensors with ultrahigh sensitivity, biological nanoprobes based on quantum effect and single photo source devices for quantum information processing. However, how to obtain highly oriented diamond films remain to be a challenge by now. This disertation mainly focus on the catalyzed growth of columnar nanocrystal diamond films by microwave plasma enhanced chemical vapor deposition(MW-PECVD) method with dynamic pressure that the pressure was gradually increasing during deposition. The micro-area XRD(MA-XRD), Raman Spectrum, XPS and SEM were employed to characterize the nanodiamond films, and synthesis mechanism of nanodiamond columnar crystals were discussed based on principle of dynamics.1) Comparing the structure of diamond particles that were deposited on Si-Ni, Si(100) and Siw-Ni, the results showed that the size ranged from5nm to100nm on Si-Ni, while it was1-2μm on Si(100), and it was about500nm on Siw-Ni.2) The morphologies and densities of diamond were obviously affected by the pretreatment time that were Omin,30min and60min under the same conditions. The films were excellent when the substrates were pretreated for30-60min.3) The densities of diamond were low when the substrate temperature were800℃and850℃; while700℃and750℃, the densities increased, and preferred orientation structure of diamond both were (220); SP3took up about75%for the total carbon bond when it was700℃. When the substrate temperature was750℃, SP3took up only65%.4) When the microwave power was1200W, the films were smooth and densities; the surface was rough and the particles were non-uniform when it was1000W; there were obvious outlines on the surface, but it presented nanostructure when it was900W.5) The size ranged from2μm to5μm when the pressure was above5.00KPa, and it was5-200nm, conversely; and it was benefitial to synthesize excellent nanodiamond under the pressure of about4.00KPa.Based on the front study, we obtained the optimum conditions to synthesize columnar nanocrystal diamond, columnar nanocrystals were obtained that they varied from200nm to300nm for the longitudinal and presented approximately20nm for the lateral when the temperature was700℃, most of them were vertical to the substrate. While the the temperature was750℃, the columnar nanocrystals were shorter and bigger, and presented anisotropic growth for different district. The mechanism of columnar nanocrystals diamond growth would be explained by dynamical equation that the driving force of nanodiamond growth was dramatically affected by the partial pressure of C during the vapor phase epitaxial growth. When the pressure was low, the force was weak and formed nanoparticles; while under the higher pressure, the force dramatically increased and also the growth rate, as a result, the columnar nanocrystal diamond was growing.