Effect of LPHT annealing on interface characteristics between HPHT Ib diamond substrates and homoepitaxial CVD diamond l
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THE SCIENCE AND TECHNOLOGY OF VAPOR PHASE PROCESSING AND MODIFICATION OF SURFACES
Effect of LPHT annealing on interface characteristics between HPHT Ib diamond substrates and homoepitaxial CVD diamond layers Xiaohua Zhu1, Jinlong Liu1,a), Siwu Shao1, Yun Zhao1, Juping Tu1, Liangxian Chen1, Junjun Wei1, Chengming Li1,b) 1
Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, People’s Republic of China Address all correspondence to this author. e-mail: [email protected] b) This author was an editor of this journal during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www.mrs.org/editor-manuscripts/. a)
Received: 4 September 2019; accepted: 12 December 2019
To study the interface characteristics between substrates and homoepitaxially grown single crystalline diamond layers, the high-pressure/high-temperature Ib diamond seeds with homoepitaxial diamond layers were annealed by low-pressure/high-temperature treatment in a hydrogen environment. The stress evolution and related impurity transformation near the interface were characterized by Raman spectroscopy, photoluminescence, and micro-infrared spectroscopy before and after annealing. It is found that the stress is the smallest in a 100 lm wide zone near the interface, accompanying with the similar change in substitutional nitrogen (Ns) concentration. After annealing at 1050 °C, 1250 °C, and 1450 °C, the local compressive stress is released gradually with temperature change. It is decreased by 1.03 GPa in maximum after annealing at 1450 °C. The concentration of nitrogen–vacancy (NV) complexes in the chemical vapor deposition (CVD) layer is dramatically reduced at 1450 °C. The value of INV- =Idiamond decreases much more than INV0 =Idiamond in the CVD layer, which is due to the lower stability of NV− compared with NV0 at high temperature.
Introduction Diamond is an exceptional material, known for its extreme hardness, high thermal conductivity, and excellent electrical properties. For the homoepitaxially grown diamond on the substrate seeds in a chemical vapor deposition (CVD) process, the source of stress in the epitaxial diamond layer comes from the various impurities and defects, which may arise from three aspects. (i) The typical defects existing in the homoepitaxial diamond originate from the dislocations in the substrate. It has been attributed to the lattice constant difference between substrate and epitaxial growth layer, resulting from the crystal imperfections in the lattice due to the presence of impurities [1, 2] or different thermal expansion coefficients between the substrate and epitaxial layer [3, 4]. (ii) Some defects in the homoepitaxial layers originate from the substrate surface defects introduced mainly during mechanical polishing. The substrate surface quality is an important factor for high-quality single crystal diamond growth. Metal inclusions on the
ª Materials Research Society 2020
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