Research On Mosaic Growth Of High Quality Large Size Single Crystalline Diamond

Diamond has a probability to become an irreplaceable material deal to its super hardness, high thermal conductivity, excellent optical and electrical properties. Detailed theoretical analysis and experimental research has been carried out in this subject with the topic mosaic growth of high quality large size single crystaline diamond, for increasing in size severely limited by the size of substrate. Using mosaic method by arranging several pieces of HPHT seeds, diamond growth will together on several pieces of substrates and integrate to a whole synthetic, aiming to have a breakthrough of the limitation on the size of the epitaxial layer enlargement and avoid the problem of the polycrystalline growth factor generated on boundaries, to obtain a large single crystal CVD diamond layer.First, chemical essence of the growth pattern of single crystal diamond initial deposition process by analysis and experimental demonstration. Chemical reaction of the CVD growth process was studied, and the influence of several important components, such as atoms [H], CH* as well as the relevant reaction equation extent impact on the reaction rate. Through experiments and theoretical analysis, initial homoepitaxial growth mode for the island growth to step-flow pattern transition was discussed. What’s more, during the growth process, attachments will be embedded in the CVD layer, resulting in lattice distortion and inner-stress. Deep dislocations or inclusions revealed by large etch pits also with lattice mismatch, dislocations and expand, will strongly affect the quality of CVD epitaxial grown by forming high defect density inside the CVD layer.Growth of single crystal diamond for a more systematic analysis of the quality and factors of its growth rate were studied. By using the method such as PL spectra, X-ray rocking curve and the plasma etching process, characterization of substrate quality and defect density, summarizing the standard of high quality HPHT substrate. In addition, polishing of side walls, temperature, microwave power, methane concentration and impurity elements, have great impacts on the growth rate and quality of CVD layer. Polycrystalline phase will be delayed if the side walls were polished, thus enhance the possibility of increased area of growth layer. Moreover, the higher the temperature or the higher the concentration of methane, the faster the growth rate, resulting a relatively lower crystal quality. That’s why a moderate growth process with pressure 320 mbar, MW power 4600 W and temperature of 850 ℃ were applied to obtain a high quality single crystal CVD diamond growth layer under high growth rate.Exploration on the mosaic growth were carried out by experimental study, to achieve a breakthrough increasing on CVD area. Interface of double pieces substrate growth were studied to explore the influence of substrate factors. Furthermore, crystal quality, defect and doping concentration were characterized. Meanwhile, sample of double pieces mosaic growth were laser cut and polished, and the cross-section of the at the interface were tested using Raman mapping method, which result that as thickening of CVD layer at the interface, width of stress zone is gradually increased due to lattice mismatch and defects. FWHM of Raman peak also increased, indicating the decrease of the crystal quality within the stress zone, and arise of defect density. The point of maximum Raman peak shift always correspond to the highest peak FWHM, revealing the location of splice interface. In addition, the three-seeds and four-seeds mosaic growth were studied to explore the morphology of splicing at the interface of the impact and the N doping concentration, large-size mosaic single crystal diamond was obtained.