Site-specific electrical contacts with the two-dimensional materials

Abstract

Electrical contact is an essential issue for all devices. Although the contacts of the emergent two-dimensional materials have been extensively investigated, it is still challenging to produce excellent contacts. The face and edge type contacts have been applied previously, however a comparative study on the site-specific contact performances is lacking. Here we report an in situ transmission electron microscopy study on the contact properties with a series of 2D materials. By manipulating the contact configurations in real time, it is confirmed that, for 2D semiconductors the vdW type face contacts exhibit superior conductivity compared with the non-vdW type contacts. The direct quantum tunneling across the vdW bonded interfaces are virtually more favorable than the Fowler-Nordheim tunneling across chemically bonded interfaces for contacts. Meanwhile, remarkable area, thickness, geometry, and defect site dependences are revealed. Our work sheds light on the significance of contact engineering for 2D materials in future applications.

Interface‐Modulated Resistive Switching in Mo‐Irradiated ReS2 for Neuromorphic Computing

“…Besides, it is worth noting that interfacial properties between the metal and the 2D TMDC materials also play a critical role in the functionality of a memristor. [29][30][31] Due to the 2D quantum confinement in TMDCs, their charge carrier transport is significantly influenced by the intrinsic defects and extrinsic effects. Transition metal substitutional doping has been extensively investigated to modulate the electrical conductivity in a 2D semiconductor by introducing charge carriers.…”

Sub‐Nanometer Electron Beam Phase Patterning in 2D Materials

“…During the process of parallel e – beam exposure on 1L ReS 2 , an in situ tungsten STM tip is manipulated to make electrical contact with the generated T/T’ phase area, and I‐V signals were sequentially recorded (Figure 4c,d ). Similar to our previous work, [ 24 ] the contact between the tungsten (W) tip and the 1L‐ReS 2 sample is ensured mechanically stable by multiple and repeatable IV testing to maintain a constant contact area. The measured conductivities, therefore, directly reflect the evolution of local conductance of the contact [ 24 ] within the e – beam exposed area.…”

“…Similar to our previous work, [ 24 ] the contact between the tungsten (W) tip and the 1L‐ReS 2 sample is ensured mechanically stable by multiple and repeatable IV testing to maintain a constant contact area. The measured conductivities, therefore, directly reflect the evolution of local conductance of the contact [ 24 ] within the e – beam exposed area. In comparison with typical electrical contact results for the new T phase (Figure 4d,e ), the electrical conductance for the contact is significantly increased tenfold by e – beam exposure for 54 s and then increased to 37‐fold after 270 s exposure.…”

“…Theoretical electronic band structures (Figure 1b–d ) clearly show that the T and T’ phases of 1L ReS 2 are both metallic, irrespective of strain conditions (Figure S12 , Supporting Information). We further performed in situ TEM‐STM experiments [ 24 ] to locally probe the electrical conductivities of the newly patterned T/T’ phases. During the process of parallel e – beam exposure on 1L ReS 2 , an in situ tungsten STM tip is manipulated to make electrical contact with the generated T/T’ phase area, and I‐V signals were sequentially recorded (Figure 4c,d ).…”

Mitigation of Edge and Surface States Effects in Two‐Dimensional WS2 for Photocatalytic H2 Generation

“…[23] In addition to the reasonable electrical conductivity displayed by the edge-to-edge configuration resulting from flakes alignment in the direction parallel to the substrate, fine inspection of the films properties has revealed the importance of the charge transport towards the back electrode. [23] Because charge carrier collection was shown to be a crucial point to achieve high photoelectrochemical performances in 3D nanoporous architectures constructed from 2D nanosheets, [35][36][37] a strategy based on patch-like, layered hetero-structures allowing the preservation of the high surface area was recently proposed. These patchlike heterostructures include WSe 2 nanoflakes partially coated both with graphene nanosheets [38][39][40] to improve charge collection and with a healing co-catalyst film.…”