Ultrathin Single‐Crystalline CdTe Nanosheets Realized via Van der Waals Epitaxy

• Published in: Advanced materials (Weinheim) Vol. 29; no. 35
• Main Authors: Cheng, Ruiqing, Wen, Yao, Yin, Lei, Wang, Fengmei, Wang, Feng, Liu, Kaili, Shifa, Tofik Ahmed, Li, Jie, Jiang, Chao, Wang, Zhenxing, He, Jun
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01-09-2017
• Subjects: 2D nanostructures; Anisotropy; cadmium telluride; Cadmium tellurides; Compatibility; Crystal growth; Crystal structure; Crystals; Dark current; Electronic devices; Epitaxy; Nanosheets; nonlayered materials; Optoelectronic devices; photodetectors; Physical properties; Silicon; Single crystals; Substrates; Symmetry; Thickness; van der Waals epitaxy; Wurtzite; 2D nanostructures; photodetectors; cadmium telluride; nonlayered materials; van der Waals epitaxy
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.201703122

Due to the novel physical properties, high flexibility, and strong compatibility with Si‐based electronic techniques, 2D nonlayered structures have become one of the hottest topics. However, the realization of 2D structures from nonlayered crystals is still a critical challenge, which requires breaking the bulk crystal symmetry and guaranteeing the highly anisotropic crystal growth. CdTe owns a typical wurtzite crystal structure, which hinders the 2D anisotropic growth of hexagonal‐symmetry CdTe. Here, for the first time, the 2D anisotropic growth of ultrathin nonlayered CdTe as thin as 4.8 nm via an effective van der Waals epitaxy method is demonstrated. The anisotropic ratio exceeds 103. Highly crystalline nanosheets with uniform thickness and large lateral dimensions are obtained. The in situ fabricated ultrathin 2D CdTe photodetector shows ultralow dark current (≈100 fA), as well as high detectivity, stable photoswitching, and fast photoresponse speed (τrising = 18.4 ms, τdecay = 14.7 ms). Besides, benefitting from its 2D planar geometry, CdTe nanosheet exhibits high compatibility with flexible substrates and traditional microfabrication techniques, indicating its significant potential in the applications of flexible electronic and optoelectronic devices.
The synthesis of large‐size ultrathin single‐crystalline CdTe nanosheets as thin as 4.8 nm via van der Waals epitaxy is demonstrated for the first time. The fabricated ultrathin CdTe photodetector shows not only ultralow dark current, high detectivity, stable photoswitching, and ultrafast photoresponse speed, but also high compatibility with flexible substrates and traditional microfabrication techniques.