Wang Peng, Song Changkun, Wang Xingfu, Chen Hedong, Qian Yinping, Rao Lujia, Zhou Guofu, Nötzel Richard
Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, People's Republic of China.
National Center for International Research on Green Optoelectronics, South China Normal University, Guangzhou 510006, People's Republic of China.
ACS Appl Mater Interfaces. 2021 Feb 17;13(6):7517-7528. doi: 10.1021/acsami.0c17835. Epub 2021 Feb 4.
An anisotropic piezoelectric response is demonstrated from InGaN nanowires (NWs) over a pyramid-textured Si(100) substrate with an interfacet composition and topography modulation induced by stationary molecular beam epitaxy growth conditions, taking advantage of the unidirectional source beam flux. The variations of InGaN NWs between the pyramid facets are verified in terms of morphology, element distribution, and crystalline properties. The piezoelectric response is investigated by electrical atomic force microscopy (AFM) with a statistic analyzing method. Representative pyramids from the ensemble, on top of which InGaN NWs grown with a substrate held at an oblique angle, were characterized for understanding and confirming the degree of anisotropy. The positive deviated oscillation of the peak force error is identified as a measure of the effective AFM tip/NW interaction with respect to the electrical contact and mechanical deformation. The Schottky contact between the metal-coated AFM tip and the NWs on the different facets reveals distinctions consistent with the interfacet composition variation. The interfacet variation of the piezoelectric response of the InGaN NWs is first evaluated by electrical AFM under zero bias. The average current monotonically depends on the scan frequency, which determines the average peak force error, that is, mechanical deformation, with a facet characteristic slope. A piezoelectric nanogenerator device is fabricated out of a sample with an ensemble of pyramids, which exhibits anisotropic output under periodic directional pressing. This work provides a universal strategy for the synthesis of composite semiconductor materials with an anisotropic piezoelectric response.
利用单向源束流，通过静态分子束外延生长条件诱导界面成分和形貌调制，在金字塔纹理化的Si(100)衬底上展示了InGaN纳米线（NWs）的各向异性压电响应。从形貌、元素分布和晶体特性方面验证了金字塔晶面之间InGaN NWs的变化。采用统计分析方法，通过电原子力显微镜（AFM）研究压电响应。对整体中的代表性金字塔进行了表征，在其顶部以倾斜角度生长了InGaN NWs，以了解和确认各向异性程度。将峰值力误差的正向偏差振荡确定为相对于电接触和机械变形的有效AFM针尖/NW相互作用的量度。金属涂层AFM针尖与不同晶面上的NWs之间的肖特基接触揭示了与界面成分变化一致的差异。首先在零偏压下通过电AFM评估InGaN NWs压电响应的界面变化。平均电流单调依赖于扫描频率，扫描频率决定了平均峰值力误差，即具有晶面特征斜率的机械变形。由具有金字塔整体的样品制造出一种压电纳米发电机器件，该器件在周期性定向按压下表现出各向异性输出。这项工作为合成具有各向异性压电响应的复合半导体材料提供了一种通用策略。
