Study On Epitaxial Growth Of Single Crystal Diamond By Microwave Plasma Chemical Vapor Deposition

Low pressure synthesis of single crystal diamond is one of the focused fields in recent years. The subject of this research presented in this paper is the growth of single crystal diamond by microwave plasma chemical vapor deposition(MPCVD). In this research, homo-epitaxial growth diamond was deposited by CVD onto HPHT diamond, which has been examined, with emphasis on producing large diamond crystal with high structural and chemical perfection.The growth of single crystal diamond should be kept in a certain range of temperature, which is the basal requirement for diamond epitaxial growth. The diamond was grown in different temperature circumstances and the right temperature range was obtained by Raman spectra. Some elements affect the substrate temperature. Besides thermal motion of the plasma and the reaction heat, the cooling conditions can also have effect. Under different cooling conditions, the diamond epitaxial is studied.The microwave power is also an important factor. When the growth temperature and other parameters are unchanged, the microwave power for diamond growth is accordance to the microwave coupling condition. At a suitable temperature, with the same chemistry conditions, the epitaxial diamond differed since the change of microwave power. Usually, the microwave coupling is not changed.To obtain large dimension single crystal diamond, high growth rate and long epitaxial time are needed. In this study, different CH4/H2 flow ratios were used to grow diamond while the other variables kept unchanged, and the relation of CH4/H2 flow ratios and the growth rate is discussed. The connections between the growth rate with pressure and fed gas flow rate were researched in the same method. The morphology of different grown conditions was also investigated by optical microscope(OM).The most important elements of growing large-size diamond is extending the epitaxial time. Because of this, long-time consequent epitaxial growth and un-consequent mutilate steps is reached. Long-time consequent epitaxial growth means that the diamond is gown as long as possible while un-consequent mutilate steps is the diamond grown for a period of time and stopped until the CVD is restated and the circulation will be continue as long as possible.