Synthesis of Ultrahigh‐Quality Monolayer Molybdenum Disulfide through In Situ Defect Healing with Thiol Molecules

Abstract

Monolayer transition metal dichalcogenides are 2D materials with many potential applications. Chemical vapor deposition (CVD) is a promising method to synthesize these materials. However, CVD‐grown materials generally have poorer quality than mechanically exfoliated ones and contain more defects due to the difficulties in controlling precursors' distribution and concentration during growth where solid precursors are used. Here, thiol is proposed to be used as a liquid precursor for CVD growth of high quality and uniform 2D MoS2. Atomic‐resolved structure characterizations indicate that the concentration of sulfur vacancies in the MoS2 grown from thiol is the lowest among all reported CVD samples. Low temperature spectroscopic characterization further reveals the ultrahigh optical quality of the grown MoS2. Density functional theory simulations indicate that thiol molecules could interact with sulfur vacancies in MoS2 and repair these defects during the growth of MoS2, resulting in high‐quality MoS2. This work provides a facile and controllable method for the growth of high‐quality 2D materials with ultralow sulfur vacancies and high optical quality, which will benefit their optoelectronic applications.

A Novel Carbon-Assisted Chemical Vapor Deposition Growth of Large-Area Uniform Monolayer MoS2 and WS2

“…Curve 2 in Figure 4 d shows the Raman spectrum obtained from the substrate at point 2. The PL spectrum (Curve 1) of monolayer MoS 2 shows a strong peak at 1.84 eV ( Figure 4 e), which is consistent with the A exciton peak due to the direct bandgap of monolayer MoS 2 [ 19 , 47 ]. Curve 2 in Figure 4 e is the PL spectrum obtained from the substrate at point 2.…”

“…The Raman spectrum of monolayer MoS 2 shows that the frequency difference between the E 1 2g mode located at 382 cm −1 and the A 1g mode located at 403 cm −1 was approximately 21 cm −1 ( Figure 1 i), which is consistent with that of the reported monolayer MoS 2 [ 31 ]. Due to the direct bandgap of monolayer MoS 2 , the PL spectrum of MoS 2 shows a strong A exciton peak at 1.84 eV ( Figure 1 j) [ 19 , 47 ]. Raman and PL maps show that monolayer MoS 2 exhibited nonuniform Raman and PL peak intensities, confirming that monolayer MoS 2 had nonuniform optical and electronic properties ( Figure 1 k–m).…”

Molecule‐Upgraded van der Waals Contacts for Schottky‐Barrier‐Free Electronics

“…have developed an elegant in situ thiol molecule assisted CVD approach and the as‐grown monolayer MoS 2 have the lowest sulfur vacancy concentration among CVD samples. [ 13 ] Here, the poly(3,4‐ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS)‐induced selenium (Se) vacancy healing effect was employed to significantly reduce the Se vacancy density of the WSe 2 flakes (Experimental Section). Generally, widespread Se vacancies in CVD‐grown WSe 2 flakes are considered to function as electron doping, [ 11b,14 ] suggesting reducing Se vacancies can increase the hole density.…”

Chemical Vapor Deposition Growth of Two-Dimensional Compound Materials: Controllability, Material Quality, and Growth Mechanism

“…To minimize the density of these sulphur vacancies, our LCVD method used C12H25SH as precursor, which not only provided a continuous sulphur precursor but also in-situ repaired the sulphur vacancies during CVD growth. 9 In this way, we obtained MoS2 samples with the lowest density of sulphur vacancies (0.32 nm -2 ) among all CVD samples reported so far, as revealed by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and the corresponding simulation result (Figures 6e and 6f). And the optical quality of the LCVD-grown MoS2 was checked using PL measurements at low temperature (80 K) and showed that the full width at half maximum was 44 meV, which was closed to that of the exfoliated MoS2 (Figure 6g).…”