Origins of genuine Ohmic van der Waals contact between indium and MoS2

Abstract

The achievement of ultraclean Ohmic van der Waals (vdW) contacts at metal/transition-metal dichalcogenide (TMDC) interfaces would represent a critical step for the development of high-performance electronic and optoelectronic devices based on two-dimensional (2D) semiconductors. Herein, we report the fabrication of ultraclean vdW contacts between indium (In) and molybdenum disulfide (MoS2) and the clarification of the atomistic origins of its Ohmic-like transport properties. Atomically clean In/MoS2 vdW contacts are achieved by evaporating In with a relatively low thermal energy and subsequently cooling the substrate holder down to ~100 K by liquid nitrogen. We reveal that the high-quality In/MoS2 vdW contacts are characterized by a small interfacial charge transfer and the Ohmic-like transport based on the field-emission mechanism over a wide temperature range from 2.4 to 300 K. Accordingly, the contact resistance reaches ~600 Ω μm and ~1000 Ω μm at cryogenic temperatures for the few-layer and monolayer MoS2 cases, respectively. Density functional calculations show that the formation of large in-gap states due to the hybridization between In and MoS2 conduction band edge states is the microscopic origins of the Ohmic charge injection. We suggest that seeking a mechanism to generate strong density of in-gap states while maintaining the pristine contact geometry with marginal interfacial charge transfer could be a general strategy to simultaneously avoid Fermi-level pinning and minimize contact resistance for 2D vdW materials.

Robust Nanocapacitors Based on Wafer-Scale Single-Crystal Hexagonal Boron Nitride Monolayer Films

“…Efforts have been made to address this problem. For example, to prevent damage of MoS 2 from heavy transition metals, Kim et al employed low-thermal-energy evaporation deposition of indium, and Liu et al replaced metal deposition with the electrode transfer technique . In the fabrication of molecular electronic devices, an indirect deposition technique was adopted to avoid damage from direct atomic beams. , …”

Quantum hybridization negative differential resistance from non-toxic halide perovskite nanowire heterojunctions and its strain control

“…The marginal hole SBH then allows the appearance of ample metal induced gap states (MIGS) spatially within the TMSGeI 3 channel region and energetically between the TMSGeI 3 valence band maximum (dotted lines) and the GeI 3 Fermi levels (solid lines). Different from conventional MIGS [ 27 , 28 ], they are quantum-hybridized states entangling two GeI 3 electrode states and the special electrode-channel-electrode quantum-hybridized character can be confirmed by observing their response to finite bias voltages and corresponding transmissions. Specifically, upon increasing the applied bias, we find that until = 0.5 V (NDR peak; Fig.…”

Tunneling Spectroscopy for Electronic Bands in Multi-Walled Carbon Nanotubes with Van Der Waals Gap

“…The van der Waals (vdW) contacts between metals and low-dimensional materials do not disturb the physical properties of the low-dimensional materials at the interface [1][2][3]. For the vdW metal-semiconducting transition metal chalcogenide (TMDC) junctions, the non-perturbed interface allows a tunable Schottky barrier height with various metals having different work functions, following the Schottky-Mott rule [1].…”

“…In this case, to achieve vdW contacts between metals and TMDC, metals are mechanically transferred to the TMDC flakes. In particular, it has been revealed that thermally evaporated In metal on TMDCs can also provide the vdW interface with good contact resistance, contrary to other metals evaporated with high evaporation energy, inducing atomic defects in the TMDC layers [2][3][4][5]. For single-walled carbon nanotubes (SWCNTs), the In/SWCNT vdW interface functions as a vacuum gap, allowing vdW gap tunneling spectroscopy for the electronic band in SWCNTs [6].…”