A computational study of monolayer hexagonal WTe₂ to metal interfaces

Abstract

Monolayer (ML) hexagonal (2H) WTe2 is predicted to be the best channel material of tunnel field effect transistor (TFET) and metal–oxide–semiconductor field effect transistor (MOSFET) among ML transition‐metal dichalcogenides. Actual devices based on 2H WTe2 typically have a contact with metal. We explore for the first time the interfacial properties between ML 2H WTe2 and Sc, Ti, Pd, Pt, Ag, and Au by using ab initio electronic structure calculation and ab initio quantum transport simulations. The energy bands of ML 2H WTe2 on Sc, Ti, Pd, and Pt substrates are destroyed strongly due to strong adhesion of ML 2H WTe2 with metal substrates, and ML 2H WTe2–Sc, −Ti, −Pd, and −Pt systems are regarded as new metallic materials. Weak adhesion is formed between ML 2H WTe2 and the Ag and Au surfaces, with the electronic energy band of ML 2H WTe2 being identifiable. Ag and Au form n‐type Schottky contact with ML 2H WTe2 at the vertical direction with electron Schottky barrier height (SBH) of 0.24 and 0.49 eV, respectively. In contrast, Pd, Pt, and Ti form p‐type Schottky contact with ML 2H WTe2 in the lateral direction with hole SBH of 0.26, 0.40, and 0.63 eV, respectively. Our study not only presents a theoretical insight into the ML 2H WTe2–metal interfaces but also help in ML 2H WTe2 based device design.

Unusual Fermi‐Level Pinning and Ohmic Contact at Monolayer Bi2O2Se–Metal Interface

“…There were six layers of metal atoms in the composite system. Based on the previous studies, the top three layers were fixed to simulate the bulk metal, while the bottom three layers were free to interact with ML Bi 2 O 2 Se and made sure the composite system could be relaxed to stable states. ML Bi 2 O 2 Se had a 1.32 eV indirect band gap without the inclusion of spin–orbital coupling (Figure b), which agreed with the one of 1.20 eV of the former DFT calculations .…”

Solar Cells Based on Two-Dimensional WTe2/PtXY (X, Y = S, Se) Heterostructures with High Photoelectric Conversion Efficiency and Low Power Consumption

“…Moreover, monolayer WTe 2 is a candidate channel for high-performance and low-power tunnel field-effect transistors (TFETs). The on-current of monolayer WTe 2 TFET with 7 nm physical gate length are 1890 and 1100 mA mm –1 for high-performance and low operating power applications, respectively. , In addition, WTe 2 has the strongest spin−orbit splitting of 0.49 eV among TMDCs, originating from the d orbitals of the heavy W atoms in the valence band (VB), which qualifies it to be applied in spintronic devices. , It is obvious from the experiment of Wang et al that WTe 2 is more effective in photovoltaic cells than other TMDCs because of its smaller band gap and superior conductivity …”

Physics of electron emission and injection in two‐dimensional materials: Theory and simulation

“…For 2D/3D heterostructure composed of bulk metals (e.g., Sc, Ti, Ag, Cu, Au, Pd, Pt, Cr, Ni, etc.) in contact with TMDC monolayers of WS 2 , 178 WSe 2 , 192 WTe 2 , 193 MoS 2 , 175,194 MoSe 2 , 195 and with black phosphorene, 196 and black‐phosphorene‐analogues such as SnS 197 and SnSe 198 are studied using DFT and quantum transport simulations. Rich contact phenomena, such as the formation of n ‐type and p ‐type Schottky contacts, ohmic contacts, and the strong metalization of the 2D semiconductors by contacting metals are identified in these materials.…”

“…When 2D semiconductor is contacted by bulk metals, the 2D semiconductor can also be metalized to form a new metallic system at the contacted region. For example, the integrations of Sc, Ti, Pd, and Pt on WTe 2 193 and of Ni, Ti, and Cr on MoSe 2 195 are found to exhibit substantial metalizations. In the case of monolayer MoS 2 contacted by metal, different types of metals exhibit contrasting charge transfer behavior.…”