High-Vacuum Particulate-Free Deposition of Wafer-Scale Mono-, Bi-, and Trilayer Molybdenum Disulfide with Superior Transport Properties

Abstract

Wafer-scale MoS growth at arbitrary integer layer number is demonstrated by a technique based on the decomposition of carbon disulfide on a hot molybdenum filament, which yields volatile MoS precursors that precipitate onto a heated wafer substrate. Colorimetric control of the growth process allows precise targeting of any integer layer number. The method is inherently free of particulate contamination, uses inexpensive reactants without the pyrophoricity common to metal-organic precursors, and does not rely on particular gas-flow profiles. Raman mapping and photoluminescence mapping, as well as imaging by electron microscopy, confirm the layer homogeneity and crystalline quality of the resultant material. Electrical characterization revealed microampere output current, outstanding device-to-device consistency, and exceptionally low noise level unparalleled even by the exfoliated material, while other transport properties are obscured by high-resistance contacts typical to MoS devices.

Epitaxial Molybdenum Disulfide/Gallium Nitride Junctions: Low-Knee-Voltage Schottky-Diode Behavior at Optimized Interfaces

“…CVD MoS 2 growth proceeds substrate-aligned (epitaxial) only on a small number of substrates beyond GaN (e.g., sapphire 8 ). In this study, we use an ultra-high-vacuum compatible CVD growth technique described previously: 31 our system is capable of seamlessly (i) clean a GaN substrate by sputtering, (ii) then apply a high-temperature ammonia treatment to replace nitrogen lost during the sputtering process and generate a well-defined surface termination, and (iii) finally grow a MoS 2 film of controlled and uniform layer numberall without breaking vacuum. Figure 1 shows a schematic representation of the system (the Supporting information Figure S1 shows a photo).…”

“…Colorimetric analysis of the reflection of the filaments from the sample allows us to monitor the layer thickness during growth and to end the deposition process precisely at the desired integer layer number. 31 XPS and LEED analysis was performed after transfer of the sample to a vacuum system equipped with a Spectra RS3000 analyzer, an OCI LEED system modified for computer control of gun and sample position, as well as ancillary instrumentation such as a sputter gun and evaporation sources.…”

A Single Layer of MoS2 Activates Gold for Room Temperature CO Oxidation on an Inert Silica Substrate

“…Our initial report focused on MoS 2 films on a dry oxide SiO 2 layer on a silicon wafer substrate for electronic applications. 34 This technique is based on heating molybdenum filaments to white glow in high vacuum followed by exposure to carbon disulfide. Decomposition of the disulfide on the filament surface results in volatile MoS x precursors, which are precipitated on an inert substrate held at a temperature that affords an equilibrium of MoS 2 island growth and desorption.…”

Towards Higher Alcohol Formation using a single-layer MoS2 activated Au on Silica: Methanol Carbonylation to Acetaldehyde

“…[30][31][32][33][34][35][36] We have avoided such complications by developing a process that provides pristine single-layer MoS2 coatings over several centimeter in diameter. 37 In this work, the formation of acetaldehyde at reactor temperatures as low as 393 K, on single layer MoS2 films, decorated by nanoscale gold islands, is evident using a plug flow reactor system with on process gas chromatography. Density functional theory (DFT) modeling sheds light on the crucial carbon-carbon coupling step at the center of this finding.…”

“…To make the catalysis, we have exploited a technique for coating of inert oxides by an MoS2 films of controlled integer layer number, as reported elsewhere. 37 This earlier work 37 focused on MoS2 films on a dry oxide SiO2 layer on a silicon wafer substrate. This MoS2 growth technique is based on heating molybdenum filaments to white glow (>1500 K) under high vacuum followed by exposure to carbon disulfide.…”