Influence of Stoichiometry on the Optical and Electrical Properties of Chemical Vapor Deposition Derived MoS₂

Abstract

Ultrathin transition metal dichalcogenides (TMDCs) of Mo and W show great potential for digital electronics and optoelectronic applications. Whereas early studies were limited to mechanically exfoliated flakes, the large-area synthesis of 2D TMDCs has now been realized by chemical vapor deposition (CVD) based on a sulfurization reaction. The optoelectronic properties of CVD grown monolayer MoS2 have been intensively investigated, but the influence of stoichiometry on the electrical and optical properties has been largely overlooked. Here we systematically vary the stoichiometry of monolayer MoS2 during CVD via controlled sulfurization and investigate the associated changes in photoluminescence and electrical properties. X-ray photoelectron spectroscopy is employed to measure relative variations in stoichiometry and the persistence of MoOx species. As MoS2−δ is reduced (increasing δ), the field-effect mobility of monolayer transistors increases while the photoluminescence yield becomes nonuniform. Devices fabricated from monolayers with the lowest sulfur content have negligible hysteresis and a threshold voltage of ∼0 V. We conclude that the electrical and optical properties of monolayer MoS2 crystals can be tuned via stoichiometry engineering to meet the requirements of various applications.

Bandgap inhomogeneity of MoS2 monolayer on epitaxial graphene bilayer in van der Waals p-n junction

“…The Mo 3d peak presented in Fig ) in MoS 2 [19]. The Mo 3d 5/2 BE ¼ 229.7 eV (Mo 3d 3/2 ¼ 232.8 eV) and S 2p 3/2 BE ¼ 162.5 eV (S 2p 1/2 BE ¼ 163.7 eV) indicate an intrinsic n-type doping of the MoS 2 [20].…”

Controlled synthesis of high-quality crystals of monolayer MoS2 for nanoelectronic device application

“…Previous studies also show its excellent physical and chemical properties, including ferroelectric gating, piezoelectronic and gas-sensitive properties [10][11][12][13][14][15]. Like other 2D materials, monolayer MoS 2 can be obtained via traditional mechanical exfoliation as well as chemical vapor deposition (CVD) method [16][17][18][19][20][21]. While mechanical exfoliated monolayer MoS 2 flakes display excellent electronic and optoelectronic properties, the small size and the low production of these monolayer MoS 2 flakes hinder them from further development.…”

Growth of Transition Metal Dichalcogenides and Directly Modulating Their Properties by Chemical Vapor Deposition

“…[52,[54][55][56][57][58][59] Optical properties and superconductivity can also be modulated by these methods. [14,60] Besides, alloying is efficient to improve stability in ambient conditions. [55,61] However, due to the challenges in controlling uniform dopant distribution, many works are still under investigation.…”