Abstract

The successful exfoliation of graphene from graphite in 2004 has shown that it is possible to create stable, single and few-atom-thick layers of van der Waals materials (Novoselov et al. 2004), and these two-dimensional (2D) layered materials can exhibit fascinating and technologically useful properties different from their bulk counterparts. The most extensively studied 2D material is graphene, which is an extended honeycomb network of sp²-hybridized carbon atoms, due to its exceptional electronic, optoelectronic, electrochemical, and biomedical applications (Geim and Novoselov 2007; Geim 2009). Following graphene, there are many 2D materials that have been explored, ranging from hexagonal boron nitride (h-BN), transition metal chalcogenides (MoO₃, MoS₂, MoSe₂, WS₂, WSe₂, etc.), MXenes, to monoelemental 2D semiconductors (silicene, germanene, stanene, borophene, phosphorene, etc.) (Butler et al. 2013; Koski and Cui 2013; Song et al. 2013; Tang and Zhou 2013; Xu et al. 2013; Miró et al. 2014; Gupta et al. 2015; Kou et al. 2015; Zhao et al. 2016).