Effect Of The Shapes Of {100} Seed Crystal Surface On The Growth Of Large Single Crystal Diamonds By HPHT Gradient Temperature Method

Diamond is a valuable material.It is not only a precious gemstone,but also has many excellent properties.For example,extremely high hardness,better thermal conductivity than copper,excellent insulation,the widest band of light transmission and other limit properties.Therefore,diamond plays an important role in people's life,industrial development and cutting-edge scientific research.With the progress of the times,the demand for diamond resources in all walks of life is also increasing day by day.With the development of synthetic diamond technology,the synthetic diamond material has surpassed the natural diamond in many aspects.Due to the advantages of performance and cost,artificial diamond materials have gradually replaced natural diamond materials in many fields.Therefore,improving the production capacity of synthetic diamond is of great significance to the development of human society.At present,high temperature and high pressure temperature gradient(HTHP)is the main methods to synthesize large single crystal diamonds.For the method,seed crystal substrates are important factors affecting diamond synthesis.Compared withconventional chemical vapor deposition method(CVD),which is limited by the size of seed crystal planes,larger seeds are usually needed to grow larger crystals.High temperature and high pressure temperature gradient method(HTHP)can grow large crystal planes on very small seed crystal planes,and the relative cost of synthesis is much lower.Therefore,based on the outstanding properties,high temperature and high pressure temperature gradient method has become the most important way to synthesize large single crystals diamond in China.However,in the use of seed crystals,there is a lack of understanding of the relationship between seed crystals and synthetic crystals.On the one hand,in the actual synthesis process,only the selected small diamond with complete crystal plane can be used as seed crystal,which results in waste for the diamond production capacity and labor.On the other hand,it is not clear whether the morphology of synthetic crystals can be guided to the direction we need by adjusting the morphology of seed crystals.Therefore,in this paper,the existing problems were studied under the same pressure and temperature in NiMnCo alloy catalyst system as follows:High quality large single crystals diamond was synthesized by successfully cutting{100} crystal planes into different shapes of diamond seed crystal.The relationship between seed crystal and synthesized crystal was observed,and the synthesized crystals were tested by SEM to study the effect of seed crystals morphology on synthesized diamond crystals.The results show that the shapes of seed crystal can only be regarded as a disturbance to the initial stage of crystal growth when the ratio of length to width of seed crystal is small.Although the ratio of length to width of seed crystal will be changed,the specific morphology of the synthesized crystal can not be changed fundamentally.When the ratio of length to width of seed crystal is too large,the lower surface of synthesized crystal is prone to defects.The defects of crystal synthesized by seed crystal with large aspect ratio were observed,and the synthesizing time was prolonged continuously.The relationship between the synthesizing time and crystal defects was studied.The results show that the defects on the lower surface of the crystal will be gradually repaired by the lateral growth of the crystal with the prolongation of the synthesis time.In the same synthetic environment,the synthesis time was continuously prolonged by choosing the same size of strip seed crystals.The ratio of length to width of the synthesized crystals was observed with the change of synthesizing time,and the lateral extension velocity of the synthesized crystals was calculated.The results show that in this case,the lateral epitaxial velocity of crystals varies in different directions,and the epitaxial velocity varies with the synthesis time.Therefore,the disturbance exerted by seed crystal on crystal synthesis will be continuously corrected along with the epitaxy of crystal,and the length-width ratio of crystal will keep approaching 1 with the extension of synthesis time,which will improve the synthesis temperature crystals and change the crystal morphology from low-temperature crystal to high-temperature crystal.The influence of temperature on the length-width ratio of synthetic crystal was observed.The results show that the effect of seed crystals on the aspect ratio of high temperature crystals is weaker than that of low temperature crystals.