Vapor Deposition Techniques for Synthesis of Two-Dimensional Transition Metal Dichalcogenides

Transition metal dichalcogenides (TMDCs) are layered materials with strong in-plane covalent bonding and weak out-of-plane van der Waals bonding which is similar with graphene (Novoselov et al., 2005; Ramakrishna Matte et al., 2010). In particular, semiconducting two-dimensional (2D) TMDCs (MX2: M=Mo, W and etc., X=S, Se, Te), exfoliated from bulk TMDCs, exhibit not only good chemical stability and flexibility but also unique electronic and optical properties, including indirect-to-direct band gap transition depending on layer number, high carrier mobility (approximately 100 cm/Vs) and strong spin-orbit coupling due to their broken inversion symmetry (Mak et al., 2010; Radisavljevic et al., 2011; Wang et al., 2012; Chhowalla et al., 2013; Song et al., 2013). These peculiar properties of 2D TMDCs make it promising to be used in field-effect transistors (Radisavljevic et al., 2011; Baugher et al., 2013; Georgiou et al., 2013; Lee et al., 2013), sensors (He et al., 2012; Li et al., 2012; Late et al., 2013; Liu et al., 2014a), photodetectors (Zhang et al., 2012; Lopez-Sanchez et al., 2013; Song et al., 2015), piezoelectric (Wu et al., 2014), and solar cell (Bernardi et al., 2013; Cheng et al., 2014; Furchi et al., 2014; Lee et al., 2014a) for future applications in such as wearable and flexible electronic devices which require compact, lightweight and high electrical and optical performance (Wang et al., 2012; Song et al., 2015). One of the most important research field in 2D TMDCs is the reliable synthesis of 2D TMDCs with large area uniformity and layer number controllability. To date, the mechanical and chemical exfoliation methods have been employed to produce 2D TMDCs (Coleman et al., 2011; Eda et al., 2011; pISSN 2287-5123·eISSN 2287-4445 http://dx.doi.org/10.9729/AM.2015.45.3.119