Shedding new light on the dislocation-mediated plasticity in wurtzite ZnO single crystals by photoindentation
Shedding new light on the dislocation-mediated plasticity in wurtzite ZnO single crystals by photoindentation
复制标题
DOI：
10.1016/j.jmst.2023.02.017
复制
发表时间：
2023-03
期刊：
影响因子：
--
通讯作者：
Yan Li;X. Fang;E. Tochigi;Y. Oshima;Sena Hoshino;Takazumi Tanaka;Hiroto Oguri;S. Ogata;Y. Ikuhara;K. Matsunaga;A. Nakamura
中科院分区：
文献类型：
--
作者：
Yan Li;X. Fang;E. Tochigi;Y. Oshima;Sena Hoshino;Takazumi Tanaka;Hiroto Oguri;S. Ogata;Y. Ikuhara;K. Matsunaga;A. Nakamura
无机半导体和氧化物中位错的可塑性因其具有良好的力学和功能特性而引起了越来越多的研究兴趣。在这项研究中，我们研究了光照对具有代表性的第三代半导体材料--六方纤锌矿--氧化锌的位错塑性的影响。专门设计了(0001)45Off试件，优先激活(0001)面上的基面滑移。在4种不同的光照条件下(550 nm、334 nm、405 nm和黑暗)进行了三种类型的纳米压痕测试，包括低负载(60μN)弹入测试、高负载(500μN)纳米压痕测试和纳米压痕蠕变测试。结果表明，无论在何种光照条件下，弹入处的最大剪应力都接近于理论剪切强度。据计算，在弹出窗口中，光下的激活体积大于黑暗中的激活体积。压痕下的横截面透射电子显微镜图像显示，所有压痕诱导的位错沿一个基面滑移面呈薄板状分布在压痕下。这些由压痕引起的位错在黑暗中比在光中传播得更深，揭示了光对位错行为的抑制作用。采用解析模型估算了压头下方的弹塑性应力场。结果发现，在较高的应力水平下，位错滑移停止，这表明在光照下，Peierls势垒增加。此外，纳米压痕蠕变测试表明，光对压痕深度和蠕变速率均有抑制作用。纳米压痕蠕变在光下比在黑暗中产生更大的激活体积。
Dislocation-mediated plasticity in inorganic semiconductors and oxides has attracted increasing research interest because of the promising mechanical and functional properties tuned by dislocations. In this study, we investigated the effects of light illumination on the dislocation-mediated plasticity in hexagonal wurtzite ZnO, a representative third-generation semiconductor material. A (0001) 45ooff sample was specially designed to preferentially activate the basal slip on (0001) plane. Three types of nanoindentation tests were performed under four different light conditions (550 nm, 334 nm, 405 nm, and darkness), including low-load (60 μN) pop-in tests, high-load (500 μN) nanoindentation tests, and nanoindentation creep tests. The maximum shear stresses at pop-in were found to approximate the theoretical shear strength regardless of the light conditions. The activation volume at pop-ins was calculated to be larger in light than in darkness. Cross-sectional transmission electron microscope images taken from beneath the indentation imprints showed that all indentation-induced dislocations were located beneath the indentation imprint in a thin-plate shape along one basal slip plane. These indentation-induced dislocations could spread much deeper in darkness than in light, revealing the suppressive effect of light on dislocation behavior. An analytical model was adopted to estimate the elastoplastic stress field beneath the indenter. It was found that dislocation glide ceased at a higher stress level in light, indicating the increase in the Peierls barrier under light illumination. Furthermore, nanoindentation creep tests showed the suppression of both indentation depth and creep rate by light. Nanoindentation creep also yielded a larger activation volume in light than in darkness.