Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon, Hong Kong SAR, China.
Key Laboratory of Low Dimensional Materials and Application Technology, Ministry of Education, Xiangtan University, Hunan 411105, China.
J Mech Behav Biomed Mater. 2017 Feb;66:172-180. doi: 10.1016/j.jmbbm.2016.11.013. Epub 2016 Nov 17.
The nanoscale elastic-plastic response of single crystal 4H-SiC has been investigated by nanoindentationwith a Berkovich tip. The hardness (H) and elastic modulus (E) determined in the load-independent region were 36±2GPa and 413±8GPa, respectively. The indentation size effect (ISE) of hardness within an indentation depth of 60nm was systematically analyzed by the Nix-Gao model. Pop-in events occurring at a depth of ~23nm with indentation loads of 0.60-0.65mN were confirmed to indicate the elastic-plastic transition of the crystal, on the basis of the Hertzian contact theory and Johnson's cavity model. Theoritically calculated maximum tensile strength (13.5GPa) and cleavage strength (33GPa) also affirms the deformation due to the first pop-in rather than tensile stresses. Further analyses of deformation behavior across the indent was done in 4H-SiC by a combined technique of focused ion beam and transmission electron microscope, revealing that slippage occurred in the (0001) plane after indentation.
采用 Berkovich 压头对单晶 4H-SiC 的纳米级弹塑性响应进行了纳米压痕研究。在独立载荷区确定的硬度（H）和弹性模量（E）分别为 36±2GPa 和 413±8GPa。通过 Nix-Gao 模型对 60nm 压痕深度内的硬度压痕尺寸效应（ISE）进行了系统分析。根据 Hertz 接触理论和 Johnson 腔模型，在 0.60-0.65mN 的压痕载荷下，深度约为 23nm 处发生的弹出事件被确认为晶体的弹塑性转变的标志。理论计算的最大拉伸强度（13.5GPa）和解理强度（33GPa）也证实了首次弹出而不是拉伸应力引起的变形。通过聚焦离子束和透射电子显微镜的组合技术对 4H-SiC 的整个压痕变形行为进行了进一步分析，结果表明压痕后在（0001）面上发生了滑移。
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