Understanding metal organic chemical vapour deposition of monolayer WS₂: the enhancing role of Au substrate for simple organosulfur precursors

Abstract

We find that the use of Au substrate allows fast, self-limited WS2 mono-layer growth using a simple sequential exposure pattern of low cost, low toxicity precursors, namely tungsten hexacarbonyl and...

A Polarization Boosted Strategy for the Modification of Transition Metal Dichalcogenides as Electrocatalysts for Water‐Splitting

“…The typical diffraction peaks appearing at 14.3° and 28.9° for WS 2 /CNTsHMS are assigned to (002) and (004) planes of WS 2 . [40,41] Furthermore, the other peaks are corresponding to 2H-WS 2 (JCPDS Card No. 08-0237), which confirms the successful reaction of tungstate ions and H 2 S to form WS 2 during the synthesis process.…”

Carbon Incorporation in MOCVD of MoS2 Thin Films Grown from an Organosulfide Precursor

“…Further investigating the chemical nature of the C incorporation, we do not find evidence for the formation of possible C−Mo bondings, which would be apparent in the C 1s region at lower binding energies of around 282.8 eV. 42 Therefore, within the detection limit of our XPS study, we postulate that the C incorporation in our films is mainly composed of a graphitic C(sp 2 ) layer codeposited with MoS 2 rather than substitutional doping of C into the MoS 2 sheet, 39 Mo 2 C carbide formation, 28,42 or CH groups at chalcogen sites previously reported in synthetic TMDs. 41 This agrees with the theoretical prediction that substitution of S with C atoms at the MoS 2 edge is thermodynamically unfavorable 20 and is further supported by the experimental observation that carbide conversion of MoS 2 does not occur below 800 °C.…”

“…22,32,37 Therefore, DES is unequivocally identified as the source of C incorporation, which is consistent with previous reports of TMD growth processes using organic chalcogen precursors. 28,32,36 To further explore the role of DES as a source of C incorporation, single-source DES exposure of the SiO 2 surface was studied as a function of growth temperature. As evident from Figure 4a, there is a rising intensity of the D and G bands with increasing temperature.…”

“…However, there are still open questions about optimal MOCVD synthesis conditions depending on precursor chemistry and, in particular, the chosen chalcogen precursor ( i.e., the S or Se source). ,, While carbon-free chalcogen hydrides (H 2 S or H 2 Se) are viable precursors for TMD growth according to thermodynamic predictions , and experimental studies, ,, cost and safety considerations have motivated further research into their low-cost and less harmful organic counterparts, such as dimethyl sulfide (CH 3 ) 2 S, ,, diethyl sulfide (CH 3 CH 2 ) 2 S, ,,− diethyl disulfide (CH 3 CH 2 ) 2 S 2 , , di- tert -butyl sulfide ((CH 3 ) 3 C) 2 S, − and dimethyl selenide (CH 3 ) 2 Se. , Among these chalcogen sources, diethyl sulfide (DES) has become a popular precursor choice after the pioneering work of Kang et al and, as such, is used in our work as representative for the variety of organic chalcogen precursors. However, the use of DES brings new challenges as carbon (C) can be introduced as an unintentional film impurity due to pyrolysis side products from organic ligands. ,, Currently, there is an ongoing discussion about the location and chemical nature of such C impurities and their influence on film growth and properties.…”

Direct Electrosynthesis of Selective Transition-Metal Chalcogenides as Functional Catalysts with a Tunable Activity for Efficient Water Electrolysis

“…Figure a,b shows the high-resolution XPS spectra of the Co 2p, Fe 2p, Mo 3d, Ni 2p, and W 4f and W 5p peak regions with the fitted peak components for different transition-metal spectra of transition-metal sulfide and selenide samples, respectively. It can be clearly seen that all the observed peaks correspond to the transition-metal chalcogen bond and satellite features (Co 2p 1/2 peaks at 793.7 and 797.3 eV, Co 2p 3/2 peaks at 778.8 and 781.6 eV, and Fe 2p 1/2 and Fe 2p 3/2 peaks at 725.0 and 712.0 eV, respectively; Mo 3d 3/2 peaks at 232.6 and 235.8 eV and Mo 3d 5/2 peak at 229.4 eV; Ni 2p 1/2 and Ni 2p 3/2 peaks at 872.9 and 855.2 eV, respectively; and W 4f 5/2 , W 4f 7/2 , and W 5p 3/2 peaks at 33.7, 31.5, and 37.5 eV, respectively). − In addition, it can be seen that peaks of S 2p 1/2 , S 2p 3/2 , Se 3d 3/2 , and Se 3d 5/2 with binding energies at 163.0, 161.8, 55.7, and 54.9 eV, respectively, are assigned to the transition-metal chalcogen bond (Figures S4 and S5). − These XPS results confirm that different types of TMCs were successfully formed by the electrochemical deposition method.…”