Anisotropic defect distribution in He+-irradiated 4H-SiC: effect of stress on defect distribution
Anisotropic defect distribution in He+-irradiated 4H-SiC: effect of stress on defect distribution
复制标题
He 辐照 4H-SiC 中的各向异性缺陷分布：应力对缺陷分布的影响
DOI：
10.1016/j.actamat.2021.116845
复制
发表时间：
2021
期刊：
影响因子：
9.4
通讯作者：
Minako Kondo and Tamaki Shibayama
中科院分区：
文献类型：
--
作者：
Subing Yang;Yuki Nakagawa;Minako Kondo and Tamaki Shibayama
已知辐照引起的六方α-SiC中的各向异性溶胀会降低碳化硅的力学性能，但其相关的物理机制和微结构过程仍不十分清楚。在本研究中，采用选区He+辐照在4H-SIC中引入了允许表面法向自由扩展的各向异性膨胀条件，并用透射电子显微镜和先进的扫描电子显微镜研究了内部缺陷的分布。并与非选区He+辐照的4H-SiC和电子辐照的TEM箔4H-SiC的缺陷分布进行了比较。在He+离子辐照的4H-SiC中观察到各向异性的缺陷分布，间隙缺陷优先沿表面法线方向([0004])重新分布，负体缺陷(如空位和/或碳反位缺陷)主要位于横向([11 2‘0]和[10 1’0])。在非选择区域He+辐照和电子辐照的样品中，缺陷分布的这种各向异性显著较低。并对三种试件的应力状态进行了测量和分析。在选定的He+辐照4H-SiC区，在横向([10 1‘0]和[11 2’0])上引入了压应力，在表面法向([0004])上引入的应力很小；这种应力状态是在离子辐照开始时引入的。压应力可能抑制了横向间隙缺陷的形成，增强了缺陷分布的各向异性。
Irradiation-induced anisotropic swelling in hexagonal α-SiC is known to degrade the mechanical properties of SiC; however, the associated physical mechanism and microstructural process remain insufficiently understood. In this study, an anisotropic swelling condition where the surface normal direction was allowed to freely expand with constraint in the lateral direction was introduced in 4H-SiC using selected-area He+ irradiation, and the internal defect distribution was investigated using transmission electron microscopy (TEM) and advanced scanning TEM. The defect distribution was compared to that in non-selected-area He+-irradiated 4H-SiC and electron-irradiated TEM-foil 4H-SiC. An anisotropic defect distribution was observed in the selected-area He+-ion-irradiated 4H-SiC, with interstitial defects preferentially redistributed in the surface normal direction ([0004]) and negative volume defects (such as vacancies and/or carbon antisite defects) dominantly located in the lateral directions ([11 2¯ 0] and [10 1¯ 0]). This anisotropy of the defect distribution was substantially lower in the non-selected-area He+-irradiated and electron-irradiated samples. The stress condition in the three samples was also measured and analyzed. In the selected-area He+-irradiated 4H-SiC, compressive stress was introduced in the lateral directions (([10 1¯ 0] and [11 2¯ 0])), with little stress introduced in the surface normal direction ([0004]); this stress condition was introduced at the beginning of ion irradiation. The compressive stress likely inhibits the formation of interstitial defects in the lateral directions, enhancing the anisotropy of the defect distribution in SiC.