CHEN Menghuan 1,2, YI Jian 2, MAN Weidong 1, JIANG Nan 2
(1. School of Materials Science and Engineering, Wuhan Institute of Technology, Wuhan 430074, Hubei, China; 2. Ningbo Institute of Materials Technology & Engineering, Chinese Academy of Sciences, Ningbo 315201, Zhejiang, China)
Abstract: Single crystal-polycrystalline diamond composite wafers were developed by using microwave plasma chemical vapor deposition (MPCVD) at 950 ℃ and methane concentration of 1.0%, with polycrystalline diamond as the support and single crystal diamond as the inlaid body. Interface of composite wafers was characterized by using scanning electron microscopy (SEM), microscopic Raman spectroscopy and infrared (IR) spectroscopy. When the methane concentration is lower than 1.0%, the interface is not well spliced, with the presence of gaps. As the methane concentration is higher than 1.0%, the single crystal has poor quality and light transmittance. In addition, the methane concentration has effects on both the size and surface roughness of the grains. At the same time, the effect of temperature (850 ℃, 950 ℃, 1050 ℃ and 1150 ℃) was also evaluated. According SEM and Raman results, it is found that the optimal temperature is 950 ℃. Lower temperatures result in poor quality of diamond nucleation, while higher temperatures lead to polycrystallization of the diamond single crystal. The temperature has a great impact on crystal orientation and growth rate. Furthermore, the single-crystal diamond, polycrystalline diamond and composite wafers were all studied by using infrared thermography. It is observed that the heat conduction rate of the composite wafers is increased by 24.2% within 0-100 s.
Key words: diamond; MPCVD; interface; splice; thermal conductivity