One-Step Synthesis of NbSe₂/Nb-Doped-WSe₂ Metal/Doped-Semiconductor van der Waals Heterostructures for Doping Controlled Ohmic Contact

Abstract

van der Waals heterostructures (vdWHs) of metallic (m-) and semiconducting (s-) transition-metal dichalcogenides (TMDs) exhibit an ideal metal/semiconductor (M/S) contact in a field-effect transistor. However, in the current two-step chemical vapor deposition process, the synthesis of m-TMD on pregrown s-TMD contaminates the van der Waals (vdW) interface and hinders the doping of s-TMD. Here, NbSe 2 /Nb-doped-WSe 2 metal-doped-semiconductor (M/d-S) vdWHs are created via a one-step synthesis approach using a niobium molar ratio-controlled solution-phase precursor. The one-step growth approach synthesizes Nb-doped WSe 2 with a controllable doping concentration and metal/doped-semiconductor vdWHs. The hole carrier concentration can be precisely controlled by controlling the Nb/(W + Nb) molar ratio in the precursor solution from ∼3 × 10 11 /cm 2 at Nb-0% to ∼1.38 × 10 12 /cm 2 at Nb-60%; correspondingly, the contact resistance R C value decreases from 10 888.78 at Nb-0% to 70.60 kΩ.μm at Nb-60%. The Schottky barrier height measurement in the Arrhenius plots of ln(I sat /T 2 ) versus q/K B T demonstrated an ohmic contact in the NbSe 2 /W x Nb 1−x Se 2 vdWHs. Combining p-doping in WSe 2 and M/d-S vdWHs, the mobility (27.24 cm 2 V −1 s −1 ) and on/off ratio (2.2 × 10 7 ) are increased 1238 and 4400 times, respectively, compared to that using the Cr/pure-WSe 2 contact (0.022 cm 2 V −1 s −1 and 5 × 10 3 , respectively). Together, the R C value using the NbSe 2 contact shows 2.46 kΩ.μm, which is ∼29 times lower than that of using a metal contact. This method is expected to guide the synthesis of various M/d-S vdWHs and applications in future high-performance integrated circuits.

Synthesis of a Selectively Nb-Doped WS2–MoS2 Lateral Heterostructure for a High-Detectivity PN Photodiode

“…In Figure f, the carrier densities of Nb-doped WS 2 and MoS 2 were estimated from the current equation of the transistor ( n 2d = I ds L / qW μ V ds , where I ds is the current, q is the electron charge, μ is the field-effect mobility, L is the channel length, and W is the channel width) . The pure WS 2 possesses a high electron density of 1.07 × 10 13 , which then reduces to 6.7 × 10 12 at 1.5 at.% Nb and finally becomes nearly zero with a greater increase in Nb concentration.…”

Two dimensional semiconducting materials for ultimately scaled transistors

“…The Schottky barrier height of such 1D edge contact is also dramatically reduced to be ∼20 meV, together with a robust mobility of ∼50 cm 2 V −1 ·s −1 . The heterophase edge contact strategy can also be extended to other 2D materials, such as the NbSe 2 /W x Nb 1-x Se 2 , MoS 2 /Mo 2 C, and PtSe 2 /PtTe 2 heterostructures synthesized by the in-situ selenization in large area arrays ( Choi et al., 2019 ; Kim et al., 2022 ; Vu et al., 2021 ). Overall, the bottom-up growth of the lateral heterophase structure demonstrates great potential to achieve edge-contacted 2D transistors on the wafer scale.…”

Atomic-Scale Insights into Comparative Mechanisms and Kinetics of Na–S and Li–S Batteries

“…Robertson et al revealed that single-atom substitutional doping of V instead of Mo results in states near the Fermi level, which has a significant impact on the electronic structure of the MoS 2 monolayer . For numerous electrocatalysis applications, WSe 2 has been proven to be an efficient contender, and doping with SAC has been used to enhance its applicability in recent investigations. − Ni et al revealed that Pd, Ag, Au, and Pt-doped monolayer WSe 2 significantly affect CO 2 , NO 2 , and SO 2 gas molecule adsorption . Zhang et al identified dynamic structural evolution in Co-doped WSe 2 nanosheets, which leads to an optimum electronic state of Se active sites and promotes H 2 generation under the hydrogen evolution reaction .…”