Fig. 1. Material characterizations of MoS2; (a) schematic diagram showing the chemical synthesis of MoS2; (b–d) SEM images showing different growth stages of MoS2 with different reaction times of 5, 12, and 30 min, respectively. Scale bars, 10 μm; (e) AFM topography of MoS2 film on SiO2 substrate. Bottom and top white profiles indicate bilayer and trilayers, respectively. Scale bar, 1 μm; (f) optical image of large-area MoS2 film transferred onto PDMS substrate.

Fig. 2. Spectroscopic characterizations of MoS2 films; (a) Raman spectra of few-layer MoS2 on SiO2/Si substrate; (b) PL spectrum of few-layer MoS2 film; (c) UV−visible spectrum of few-layer MoS2 film on quartz.

Fig. 3. (a) TEM image showing folded MoS2 film. Scale bar, 100 nm; (b) HRTEM image of MoS2 film. Scale bar, 5 nm. Inset, corresponding electron diffraction pattern; (c) XPS spectrum of MoS2 thin film; (d) XRD result for MoS2 thin film.

Fig. 4. (a) Typical transfer curve for MoS2 transistor. Inset, optical image of a FET device. Scale bar, 100 μm; (b) output curve for MoS2 transistor.