Atomically Thin Ohmic Edge Contacts Between Two-Dimensional Materials

Abstract

With the decrease of the dimensions of electronic devices, the role played by electrical contacts is ever increasing, eventually coming to dominate the overall device volume and total resistance. This is especially problematic for monolayers of semiconducting transition metal dichalcogenides (TMDs), which are promising candidates for atomically thin electronics. Ideal electrical contacts to them would require the use of similarly thin electrode materials while maintaining low contact resistances. Here we report a scalable method to fabricate ohmic graphene edge contacts to two representative monolayer TMDs -MoS2 and WS2. The graphene and TMD layer are laterally connected with wafer-scale homogeneity, no observable overlap or gap, and a low average contact resistance of 30 kΩµm. The resulting graphene edge contacts show linear current-voltage (IV) characteristics at room temperature, with ohmic behavior maintained down to liquid helium temperatures.3

Progress on Electronic and Optoelectronic Devices of 2D Layered Semiconducting Materials

“…This configuration leads to the high electronic performance of graphene, including a room‐temperature mobility up to 140 000 cm 2 V −1 s −1 , comparable to the theoretical phonon‐scattering limit, and low‐temperature ballistic transport over 15 µm distances. Guimarães et al developed an in situ heterostructure growth method to realize a lateral MoS 2 /graphene contact, which brings about a low average contact resistance of 30 kΩ µm.…”

Properties of in-plane graphene/MoS 2 heterojunctions

“…Examples include in-plane stitching of (i) one-atom-thick sheets, like graphene/hexagonal boron nitride (h-BN), 15,16 (ii) different TMDC systems or phases, [17][18][19][20][21] like MoSe 2 /WSe 2 or 1T/2H phase boundaries of MoS 2 , and (iii) one-atom-thick sheet and TMDC, like graphene/MoS 2 . [22][23][24][25] These systems provide a promising platform for realizing low-resistance contacts between 2D metals and 2D semiconductors, 5,11,21 that can be assembled into field-effect transistors (FETs) with remarkable performance. [20][21][22][23][24] To improve the device performance of 2D MSJ, a better fundamental un-derstanding of its electronic properties and operating mechanism is needed.…”

“…[22][23][24][25] These systems provide a promising platform for realizing low-resistance contacts between 2D metals and 2D semiconductors, 5,11,21 that can be assembled into field-effect transistors (FETs) with remarkable performance. [20][21][22][23][24] To improve the device performance of 2D MSJ, a better fundamental un-derstanding of its electronic properties and operating mechanism is needed. Recently, Yu et al reported a model study based on semiclassical macroscopic theory, 26 that suggests a highly nonlocalized charge transfer and strong reduction of FL pinning in 2D MSJs.…”

Atomic layer deposited oxide films as protective interface layers for integrated graphene transfer

“…Extensive process calibration was required to avoid leaving oxide residues or damaging the graphene. Although we note that complete etching of the graphene might be beneficial in the contact area to lower contact resistance by producing edge contacts (side contact instead of top contact) [63][64][65].…”