Oriented lateral growth of two-dimensional materials on c-plane sapphire

• Published in: Nature nanotechnology Vol. 18; no. 11; pp. 1289 - 1294
• Main Authors: Fu, Jui-Han, Min, Jiacheng, Chang, Che-Kang, Tseng, Chien-Chih, Wang, Qingxiao, Sugisaki, Hayato, Li, Chenyang, Chang, Yu-Ming, Alnami, Ibrahim, Syong, Wei-Ren, Lin, Ci, Fang, Feier, Zhao, Lv, Lo, Tzu-Hsuan, Lai, Chao-Sung, Chiu, Wei-Sheng, Jian, Zih-Siang, Chang, Wen-Hao, Lu, Yu-Jung, Shih, Kaimin, Li, Lain-Jong, Wan, Yi, Shi, Yumeng, Tung, Vincent
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.11.2023; Nature Publishing Group
• Subjects: 140/133; 639/166; 639/301; Aluminum; Chalcogenides; Chemistry and Materials Science; Crystals; Docking; Electrical properties; Epitaxial growth; Epitaxy; Exposure; Grains; Homogeneity; Materials Science; Monolayers; Nanotechnology; Nanotechnology and Microengineering; Nucleation; Oxygen; Perovskites; Sapphire; Single crystals; Stitching; Substrates; Transition metal compounds; Two dimensional materials
• ISSN: 1748-3387; 1748-3395; 1748-3395
• DOI: 10.1038/s41565-023-01445-9

Two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) represent the ultimate thickness for scaling down channel materials. They provide a tantalizing solution to push the limit of semiconductor technology nodes in the sub-1 nm range. One key challenge with 2D semiconducting TMD channel materials is to achieve large-scale batch growth on insulating substrates of single crystals with spatial homogeneity and compelling electrical properties. Recent studies have claimed the epitaxy growth of wafer-scale, single-crystal 2D TMDs on a c -plane sapphire substrate with deliberately engineered off-cut angles. It has been postulated that exposed step edges break the energy degeneracy of nucleation and thus drive the seamless stitching of mono-oriented flakes. Here we show that a more dominant factor should be considered: in particular, the interaction of 2D TMD grains with the exposed oxygen–aluminium atomic plane establishes an energy-minimized 2D TMD–sapphire configuration. Reconstructing the surfaces of c -plane sapphire substrates to only a single type of atomic plane (plane symmetry) already guarantees the single-crystal epitaxy of monolayer TMDs without the aid of step edges. Electrical results evidence the structural uniformity of the monolayers. Our findings elucidate a long-standing question that curbs the wafer-scale batch epitaxy of 2D TMD single crystals—an important step towards using 2D materials for future electronics. Experiments extended to perovskite materials also support the argument that the interaction with sapphire atomic surfaces is more dominant than step-edge docking. Interaction of two-dimensional transition metal dichalcogenide grains with exposed oxygen–aluminium atomic plane in sapphire is a more dominant factor than step-edge docking in controlling the single-crystal epitaxy of these materials.