Engineering covalently bonded 2D layered materials by self-intercalation

• Published in: Nature (London) Vol. 581; no. 7807; pp. 171 - 177
• Main Authors: Zhao, Xiaoxu, Song, Peng, Wang, Chengcai, Riis-Jensen, Anders C., Fu, Wei, Deng, Ya, Wan, Dongyang, Kang, Lixing, Ning, Shoucong, Dan, Jiadong, Venkatesan, T., Liu, Zheng, Zhou, Wu, Thygesen, Kristian S., Luo, Xin, Pennycook, Stephen J., Loh, Kian Ping
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.05.2020; Nature Publishing Group
• Subjects: 639/301/357/1018; 639/925/930/328/2082; Alkali metals; Analysis; Atomic properties; Chemical bonds; Ferromagnetism; Humanities and Social Sciences; Intercalation; Kagome lattice; Lattice vacancies; Layered materials; Molecular beam epitaxy; multidisciplinary; Occupancy; Overlays and overlaying; Properties (attributes); Science; Science (multidisciplinary); Silicon wafers; Spectrum analysis; Stoichiometry; Sulfur; Tantalum; Topology; Transition metal compounds; Transition metals; Two dimensional materials; Singapore
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-020-2241-9

Two-dimensional (2D) materials 1 – 5 offer a unique platform from which to explore the physics of topology and many-body phenomena. New properties can be generated by filling the van der Waals gap of 2D materials with intercalants 6 , 7 ; however, post-growth intercalation has usually been limited to alkali metals 8 – 10 . Here we show that the self-intercalation of native atoms 11 , 12 into bilayer transition metal dichalcogenides during growth generates a class of ultrathin, covalently bonded materials, which we name ic-2D. The stoichiometry of these materials is defined by periodic occupancy patterns of the octahedral vacancy sites in the van der Waals gap, and their properties can be tuned by varying the coverage and the spatial arrangement of the filled sites 7 , 13 . By performing growth under high metal chemical potential 14 , 15 we can access a range of tantalum-intercalated TaS(Se) y , including 25% Ta-intercalated Ta 9 S 16 , 33.3% Ta-intercalated Ta 7 S 12 , 50% Ta-intercalated Ta 10 S 16 , 66.7% Ta-intercalated Ta 8 Se 12 (which forms a Kagome lattice) and 100% Ta-intercalated Ta 9 Se 12 . Ferromagnetic order was detected in some of these intercalated phases. We also demonstrate that self-intercalated V 11 S 16 , In 11 Se 16 and Fe x Te y can be grown under metal-rich conditions. Our work establishes self-intercalation as an approach through which to grow a new class of 2D materials with stoichiometry- or composition-dependent properties. The intercalation of native atoms into bilayer transition metal dichalcogenides during growth generates ultrathin, covalently bonded materials into which ferromagnetic ordering can be introduced.