Electrodeposition of MoS₂ from Dichloromethane

Abstract

The electrodeposition of MoS2 from dichloromethane (CH2Cl2) using tetrabutylammonium tetrathiomolybdate ([NnBu4]2[MoS4]) as a single source precursor is presented. The electrodeposition of MoS2 from CH2Cl2 requires addition of a proton donor to the electrolyte and trimethylammonium chloride (Me3NHCl) was used for this purpose. Electrochemical Quartz Crystal Microbalance (EQCM) experiments have been employed for a detailed study of the electrochemical mechanism and to study the role of the proton donor. EQCM reveals cathodic electrodeposition of MoS2 and anodic deposition of MoS3 as well as an additional corrosion process where the deposited MoS3 strips back into solution. The electrodeposited MoS2 films are amorphous in nature. All the films were found to be homogeneous in composition across the electrode area and to be reproducible between experiments. Annealing of the as-deposited films under a sulfur atmosphere results in crystalline MoS2 as confirmed by energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy and X-ray diffraction. The deposited films were smooth and planar, as observed with scanning electron microscopy (SEM), indicating a layer-by-layer growth typical of transition metal dichalogenides.

Lateral Growth of MoS2 2D Material Semiconductors Over an Insulator Via Electrodeposition

“…We recently reported a detailed investigation on the electrochemical processes during the CV of the same electrolyte system employing electrochemical quartz crystal microbalance (EQCM) measurements. [ 8 ] The CVs displayed in Figure 1c clearly show evidence of the cathodic reduction of [MoS 4 ] 2– ions to MoS 2 . It is clear that the CV recorded from the lateral TiN electrodes is comparable, in terms of electrochemical processes at the interface, to the CV measured on the planar TiN electrode, indicating that the electro‐reduction mechanism of the [MoS 4 ] 2– ions remains the same irrespective of the type of TiN electrode used.…”

“…The electrodeposition experiments were performed in CH 2 Cl 2 solvent using [N n Bu 4 ] 2 [MoS 4 ], which was synthesized in‐house to function as a single source precursor, providing both the Mo and S. [ 7,8 ] In contrast to [NH 4 ] 2 [MoS 4 ], which has been used in aqueous solvents, [N n Bu 4 ] 2 [MoS 4 ] has excellent solubility in CH 2 Cl 2 . The electrodeposition solution also included [N n Bu 4 ]Cl as the supporting electrolyte and trimethylammonium chloride [NHMe 3 ]Cl as the proton source, which is necessary to remove the excess S during deposition of MoS 2 from [MoS 4 ] 2– .…”

“…The electrodeposition solution also included [N n Bu 4 ]Cl as the supporting electrolyte and trimethylammonium chloride [NHMe 3 ]Cl as the proton source, which is necessary to remove the excess S during deposition of MoS 2 from [MoS 4 ] 2– . [ 8 ] The electrodeposition experiments were all performed within a glovebox equipped with a dry nitrogen circulation system to minimize moisture and ensure that oxygen levels were maintained below 10 ppm. The depositions were performed using a three electrode electrochemical cell with a Pt gauze as counter electrode and a Ag/AgCl (0.1 m [N n Bu 4 ]Cl in CH 2 Cl 2 ) reference electrode.…”

“…The as‐deposited MoS 2 film is amorphous, as X‐ray diffraction on thicker films indicate, although with some short‐range ordering present as evidenced by the preferential lateral growth. [ 8,28–30 ] An annealing step was performed to crystallize the film. The sample was annealed using a tube furnace that was set initially to 100 °C for 10 min and then 500 °C for 2 h at 0.1 mbar.…”

“…We have recently demonstrated that electrodeposition is a potentially viable method for solving this challenge. [ 7,8 ] Electrodeposition offers important advantages in 2D material production over other methods such as chemical vapor deposition (CVD), [ 9,10 ] sputtering, [ 11 ] or atomic layer deposition (ALD). [ 12 ] Electrodeposition is not a line‐of‐sight deposition method as material growth occurs at electrical contacts and is controlled by electrical potential or current.…”