Low-Dimensional Semiconductors beyond Graphene: An Insight from Theory

If graphene had a band gap, it would probably be the optimum 2D system for electronics applications. Layered transition metal dichalcogenides (TMDs) with a robust intrinsic band gap appear to be the next-best alternative. But TMD applications in electronics suffer from two limitations: the difficulty to construct transparent contacts [1], and the adverse effect of atomic defects especially in systems grown by CVD. Defects such as chalcogen vacancies scatter charge carriers and quench photoluminescence. To remedy these deficiencies, optimum strategies have been devised to make low- resistance, ohmic contacts to TMDs [2] such as MoS₂ using similar, epitaxial TMDs. Recent experimental and theoretical [3] studies suggest that exposure of defective MoS₂ to sulfur-containing compounds may effectively heal S vacancy and adatom defects. There is rapid progress in 2D systems other than graphene and TMDs, including elemental group V and group VI 2D semiconductors. Alternative coil allotropes with unusual optical and transport properties appear to self-assemble inside cylindrical cavities with few nanometers in diameter [4,5]. Predictive ab initio calculations provide useful guidance to experimental studies in this case.

References:

[1] Igor Popov, Gotthard Seifert, and David Tomanek, Phys. Rev. Lett. 108, 156802 (2012).

[2] Jie Guan, Hsun-Jen Chuang, Zhixian Zhou, and David Tomanek, ACS Nano 11, 3904 (2017).

[3] Anja Foerster, Sibylle Gemming, Gotthard Seifert, and David Tomanek, ACS Nano 11 (2017).

[4] Dan Liu, Jie Guan, Jingwei Jiang, and David Tomanek, Nano Lett. 16, 7865-7869 (2016).

[5] Jinying Zhang, Dan Zhao, Dingbin Xiao, Chuansheng Ma, Hongchu Du, Xin Li, Lihui Zhang, Jialiang Huang, Hongyang Huang, Chun-Lin Jia, David Tomanek, and Chunming Niu, Angew. Chem. Int. Ed. 56, 1850-1854 (2017).