Research On Growth Mechanism And Synthesis Experiment Of Silicon Carbide Derived Diamond

Diamond has attracted wide attention for its excellent properties. Low pressure vapor depositionand High Pressure High Temperature methods are the common techniques to synthesis artificialdiamond. Compared with the used diamond synthesis techniques, the synthesis of silicon carbidederived diamond (SCDD) film using selective etching method is an attractive technique which has theadvantage of simple process, low cost, good coating-substrate adhesion and so on. To obtain theSCDD film synthesis technique, the growth mechanism of SCDD using selective etching method, theexperimental device and the synthesis experiments were investigated in this thesis. The workaccomplished and the achievements acquired are as following:(1) The growth mechanism of diamond with selective etching technique was studied. Thesynthesis mechanism of diamond was expounded by transformation of atomic structures andthermodynamics, which indicates that large amounts of active atoms come into being with the chainreaction of Cl2and H2, large amounts of carbon clusters emerge during the SiC was etched, andsp3-bonded carbon atoms structure into diamond under activation of active atoms on carbon clusters.At the same time, the already formed C-C bond (σ bond) won’t be destroyed by active atoms. Themajor reaction forms and the appropriate ratio of Cl2and H2were presented. The “four stages model”and “layer-downing model” were established to explain the transformation and thickening process ofSCDD from silicon carbide.(2) The experimental system for SCDD film synthesis was designed and prepared successfully.The performance of the device was investigated. The distribution of flow field and temperature fieldin the reaction chamber was studied using FLUENT software. The impact of inlet flow velocity,distance between samples and air inlet, carrier gas, heating mode and other factors on the temperaturefield and flow field were analyzed. Based on the simulation results and synthesis mechanism of theSCDD film, optimization design of experimental device was carried out.(3) The synthesis experiment of SCDD film was carried out. SCDD film was prepared at Cl2/H2ratio of2:1to3:1and temperature of~950℃. Raman, XRD, nano-indentation, SEM, EDS were usedto characterize the SCDD samples. The traction of Si-C bond in silicon carbide is in favor of theformation of diamond. The mechanism of sp3-bonded carbon structure protruding from the surfaceand co-existence of sp2and sp3carbon structure was explained.