Hydrogen Plasma Exposure of Monolayer MoS₂ Field-Effect Transistors and Prevention of Desulfurization by Monolayer Graphene

Abstract

Atomic vacancies related to structural disorder and doping variation influence carrier transport in monolayer transition-metal dichalcogenide devices. Here, we investigate the effect of hydrogen plasma exposure (HPE) on monolayer MoS2 field-effect transistors (FETs). We observe that a 1% increase in sulfur vacancy after HPE results in incremental 0.06 eV of the Schottky barrier. Short-range scattering from the sulfur vacancies reduces the carrier mobility of monolayer MoS2 by 2 orders of magnitude. Despite the defects and grain boundaries formed during the chemical vapor deposition and transferring process, the surface desulfurization induced by the proton exposure and thermally accelerated oxidation can be blocked by monolayer graphene cladding with a van der Waals contact distance of 2.5 Å. The material-level study indicates a promising route for a low-cost and robust fabrication of smart sensor circuits on a monolithic MoS2 wafer, where the bare MoS2 FETs can serve as proton sensors, with their electronic readout processed by a logic circuit of graphene-protected pristine FETs with a high on/off ratio.

Effect of Large-Area Exfoliation and Etching on the Electrical Behavior of Transition-Metal Dichalcogenide Field-Effect Transistors

“…Furthermore, the result suggests the concentration of bulk trap states in the TMDC layers may be responsible for the leakage current, and this concentration decreased as a function of the MoS 2 thicknesses. This observation agrees with a previous report, which investigated the effect of inducing traps in the semiconductor bulk of TMDC-based TFTs.…”

Atomic Hydrogen Annealing of Graphene on InAs Surfaces and Nanowires: Interface and Morphology Control for Optoelectronics and Quantum Technologies

“…(b) Graphite and graphene flakes are identified on SiO 2 /Si by optical microscopy. The specific thicknesses in terms of monolayer, bilayer, and more can be obtained using the contrast on SiO 2 /Si and Raman measurements (Figure S4) prior to the transfer to the final InAs substrate. Here, the very bright blue region is single-layer graphene.…”

“…56 To transfer the graphene, we use the well-established polymer-assisted technique; 48 more details are found in the Methods and Materials section. Single/multilayer graphene is initially identified on a SiO 2 /Si wafer (highly doped Si wafers with ∼300 nm SiO 2 on top) before transferring (Figure 1b), and its thickness is estimated considering its color contrast under an optical microscope and confirmed using Raman spectroscopy 45 (Figure S4). The graphene is then transferred using polymer embedding (Figure S2) as described in the Methods and Materials section.…”

“…For III–V semiconductor NWs, this has been shown in many studies. − Annealing semiconductor surfaces in atomic hydrogen has been proven to be efficient in removing native oxides and achieving clean, defect-free surfaces . This in turn leads to improved properties of the NWs. ,,, The hydrogen radicals will react with the oxide and other contaminants on the surface to form more volatile compounds, which desorb below the temperature where the samples decompose. , However, graphene can act as a barrier for diffusion to and from the underlying substrate that can lead to an inhibition of the deoxidation processes. − Furthermore, passivation of dangling bonds at the interface between graphene and SiC was impeded at temperatures up to ∼800 °C, and as a result, the sample underneath the graphene could not be passivated. Therefore, the potential of atomic hydrogen cleaning underneath graphene is a nontrivial question with relevance for applications using the systems’ electronic or optical properties.…”

Plasma Treatment of Ultrathin Layered Semiconductors for Electronic Device Applications

“…212 H 2 plasma (P = 50 W, p = 75 mTorr, t = 240 s) was used to locally convert 2H-MoTe 2 areas to 1T′-MoTe 2 before metal deposition, decreasing the contact resistance at low temperatures by 5 orders of magnitude. 213 The approach of inducing defect-born phase transitions in TMDs 39,41 with plasma treatment 167,214,215 is relatively unexplored but may yield superlative device performance to the seamless nature of the resulting lateral heterostructure. Further explorations into this are needed to characterize the nature of the phase transitions and the defect concentrations required to reach them.…”