Fluorinated Graphene Contacts and Passivation Layer for MoS₂ Field Effect Transistors

Abstract

2D materials have been considered as promising candidates for next-generation electronics since they offer unprecedented capability in device performance at the atomic limit through synergistic combination with silicon technology. [1,2] In particular, atomically thin 2D semiconductors, such as transition metal dichalcogenides (TMDs), have a desirable range of bandgap energies in the range between 1.0 and 2.5 eV and high carrier mobility up to 200 cm 2 V −1 s −1 , [3][4][5][6] thereby allowing integration into the silicon platforms. However, there are two ubiquitous problems that 2D semiconductors share with all nanomaterial electronics: environmentally Realizing a future of 2D semiconductor-based devices requires new approaches to channel passivation and nondestructive contact engineering.Here, a facile one-step technique is shown that simultaneously utilizes monolayer fluorinated graphene (FG) as the passivation layer and contact buffer layer to 2D semiconductor transistors. Monolayer graphene is transferred onto the MoS 2 , followed by fluorination by XeF 2 gas exposure. Metal electrodes for source and drain are fabricated on top of FG-covered MoS 2 regions. The MoS 2 transistor is perfectly passivated by insulating FG layer and, in the contacts, FG layer also acts as an efficient charge injection layer, leading to the formation of Ohmic contacts and high carrier mobility of up to 64 cm 2 V −1 s −1 at room temperature. This work shows a novel strategy for simultaneous fabrication of passivation layer and low-resistance contacts by using ultrathin functionalized graphene, which has applications for high performance 2D semiconductor integrated electronics.

Broadband Photodetection of Centimeter-Scale T-Phase Gallium Telluride Grown by Molecular Beam Epitaxy

“…Additionally, we have further confirmed that GaTe is identified as a p-type semiconductor from the Hall measurements. The carrier concentration decreases with the increase of temperature, and the carrier mobility increases with temperature, which is close to 100 cm 2 V –1 s –1 at room temperature, , demonstrating that T-GaTe is suitable for the preparation of high-performance devices. The temperature-dependent carrier concentration and mobility are contrary to the expected behavior of ordinary semiconductors, possibly because the opposite-type carrier is also generated over the measured temperature range, with a concentration greater than the increment of the dominant carrier, and the overall transport could be dominated by a ballistic nature .…”

Multi-Layer Palladium Diselenide as a Contact Material for Two-Dimensional Tungsten Diselenide Field-Effect Transistors

“…More recently, semi-metallic contacts such as bismuth, antimony, and graphene have shown promising results [ 37 , 38 , 39 ]. However, semi-metal depositions involve heating of the substrate up to 100 °C to achieve a particular orientation of the metal (Sb 011 on ), which tends to introduce defects into heat-sensitive 2D semiconductors with ambipolar functionality, such as [ 40 , 41 ] and black phosphorus [ 42 ].…”

Selected Area Manipulation of MoS2 via Focused Electron Beam-Induced Etching for Nanoscale Device Editing

“…Spontaneous XeF 2 vapor etching of 2D TMDs has also been explored for layer thinning and device fabrication when combined with nanolithography. , Conveniently, graphene is not spontaneously etched in XeF 2 , so it is an adequate etch stop for MoS 2 . Interestingly, fluorination of graphene causes sp 3 -type defects, as evidenced in the Raman D peak increase, which reduces the conductivity, whereas fully fluorine-passivated graphene is insulating. , …”

“…Interestingly, fluorination of graphene causes sp 3 -type defects, as evidenced in the Raman D peak increase, which reduces the conductivity, whereas fully fluorinepassivated graphene is insulating. 41,42 Here, we systematically explore FEBIE of MoS 2 mediated by an XeF 2 precursor. As our local pressures are much lower than previous spontaneous etching studies, negligible spontaneous etching is observed in what is presented, and we attribute the etching to synergistic electron-XeF 2 precursor interactions with the MoS 2 .…”