MXene Electrode for the Integration of WSe₂ and MoS₂ Field Effect Transistors

Abstract

1wileyonlinelibrary.com mobility. In TMD-based FETs, Schottky junction contacts are formed between the source/drain electrode and the channel, so the barrier heights at the junction interfaces have important roles in the polarity and performance of such devices. [8,9] Therefore, appropriate electrode materials are required for TMD-based devices. As a gapless semi-metal material, [10] graphene is an important material for 2D electrodes owing to its high conductivity and transparency. A vertically stacked grapheneMoS 2 FET was first reported by Duan et al., [11] and found to exhibit a high current density and a high on-off ratio when graphene was used as a tunable source electrode. Since this study, graphene electrodes have been more extensively tested, [12,13] and found to exhibit better electrical performance than other metal electrodes. Flexible and transparent MoS 2 FETs, in which graphene serves as a gate electrode and boron nitride acts as the dielectric layer, have also been demonstrated by Lee et al., [12] which enables the integration of FETs with 2D electronic components. Although the work function of graphene can be tuned with an electric field, which modulates the Schottky barrier height, [14] graphene's cone band structure means that this barrier height does not vary significantly under large gate voltages because the Fermi level of graphene is far from the Dirac point and exists in the region with a high density of states. [12] The relatively low work function of graphene (≈4.6 eV) and its small tuning range [12,14] mean that it has been primarily utilized in n-channel FET electrodes.Recently, newly emerging MXene 2D materials have attracted much attention. In general, MXenes are obtained by selectively etching A from a MAX phase, where M is an early transition metal, A is mostly a group IIIA or IVA element, and X is C or N. [15] During the etching process, the A atoms, which act as glue between the M n+1 X n layers (n = 1, 2, or 3), are removed and replaced by surface groups. The remaining M n+1 X n layers with surface groups are labeled an MXene because of their graphene-like 2D nature. Mxenes are now widely studied in lithium battery applications because of their high capacities and good conductivity. [16] MXenes are also potential candidates for 2D FET electrodes. Naguib et al. [17] showed that MXene materials have low-sheet resistivities that are comparable to that of multilayer graphene. Halim et al. [18] claimed that Ti 3 C 2 films synthesized via deposition and subsequent etching steps can achieve 90% transmission of light

Growth of WS2 flakes on Ti3C2Tx Mxene Using Vapor Transportation Routine

“…Wu et al used MoS 2 decorated Ti 3 C 2 mxene as electrode and greatly enhanced the capacity of sodium-ion batteries [14]. Xu et al used Ti 2 C(OH) x F y as a novel electrode material and greatly reduced the Schottky barrier height between electrode and WSe 2 [15]. Regarding this progress, the WS 2 /Ti 3 C 2 T x structure had not been synthesized.…”

Schottky-Barrier-Free Contacts with Two-Dimensional Semiconductors by Surface-Engineered MXenes

“…transition metal dichalcogenides, black phosphorus) have attracted great interest, their development is significantly hindered by the large Schottky barrier (SB) at the metal-semiconductor junction (MSJ). [14][15][16] Very recently, the use of Ti 2 CT x as electrodes for 2D MoS 2 and WSe 2 field effect transistors have been experimentally demonstrated, yet with significant SBs 17 . Here we predict that SB-free contacts can be achieved by using MXenes with proper surface terminations, which form van der Waals (vdW) junctions 16,18,19 with 2D semiconductors.…”

MXene‐Based Composites: Synthesis and Applications in Rechargeable Batteries and Supercapacitors

“…[127] In addition to the hydrothermal method, the mechanical transfer technique has also been used to prepare a MoS 2 /Ti 3 C 3 T x heterostructure and a WSe/Ti 3 C 3 T x heterostructure. [197] When the MO and MS/MXene composites are obtained by a simple ex-situ method, the uniform distribution of oxides and sulfides is limited. Moreover, with ball-milling method it is not easy to control morphology.…”

“…For example, Ti 3 C 2 T x /g-C 3 N 4 composite was successfully synthesized by a solution mixing method. [48,197] In addition to g-C 3 N 4 , the composite obtained by theoretical calculation of a blue phosphorene with a graphene structure and MXene has demonstrated outstanding mechanical flexibility. Because both surfaces of the Ti 3 C 2 T x and g-C 3 N 4 carry different potential, they do not aggregate or precipitate, but form a stable colloidal solution.…”

“…The effect produces a change of the MXene surface, and the charge distribution will alter. [59,77,197] [232] Some individual MXene-based composites can absorb electromagnetic waves so that the specialized composites materials can be used in the electromagnetic wave absorption apparatus.…”