Fig. 1. (a) Concentrations of MoS2 dispersion at different rotation speeds with related optical images inserted. (b) Tauc plot of MoS2 dispersions. (c) Size and height of MoS2 dispersions at different rotation speeds. (d), (g) AFM image and height profile of MoS2 at 2000 rpm. (e), (h) AFM image and height profile of  MoS2 at 4000 rpm. (f), (i) AFM image and height profile of MoS2 at 6000 rpm. The number indicates the different nanosheet.

Fig. 2. Representative TEM images of MoS2 dispersions at (a) 0, (b) 2000, (c) 4000, (d) 6000, and (e) 8000 rpm. (f) High-resolution TEM image of MoS2 nanosheet at 6000 rpm. (g) TEM image of ultrathin layer of MoS2 defect at 8000 rpm; elemental mapping of (h) Mo (i) S.

Fig. 3. (a) High-resolution XPS spectra of MoS2 films. (b) XRD patterns of MoS2 films. (c) Raman spectra of MoS2 films. (d) Raman shift of E2g1 and A1g. (e) UV-Vis absorption spectra of MoS2 films. (f) Tauc plot obtained from UV-Vis absorption spectra of MoS2 films with an increase in centrifugation speed.

Fig. 4. Open-aperture Z-scan results of MoS2 dispersions (a) at 0 rpm with different pulse energies, (b) at 6000 rpm with different pulse energies, and (c) at different rotation speeds. Z-scan results of MoS2 films (d) at 8000 rpm and different pulse energies, at different rotation speeds (e) with 45 nm thickness and (f) 75 nm thickness.

Fig. 5. (a) Calculated results of α0 (red dot) and βeff (blue square), respectively. (b) Im χ(3) and FOM from MoS2 dispersions in red dot and blue square, respectively. (c) Measured α0 (red dot) and βeff (blue square). (d) Im χ(3) and FOM from films with different sizes, which are shown using red dot and blue square, respectively.

Fig. 6. Band structure and DOS results for monolayer MoS2: (a) perfect; (b) with monosulfur vacancy; and (c) with disulfur vacancy.

Fig. 7. (a) Three-energy-level model of few or few-defect MoS2. (b) Three-energy-level model combined with defect state of S vacancies in MoS2. (c) Three-defect-energy-level diagram at a high concentration of S vacancies in MoS2. Fitting results of (d) MoS2 dispersions at different rotation speeds, MoS2 films (e) with 45 nm thickness and (f) with 75 nm thickness.

Table 1. Parameters of MoS2 Dispersions and Films