Although many prototype devices based on two-dimensional (2D) MoS2 have been fabricated and wafer scale growth of 2D MoS2 has been realized, the fundamental nature of 2D MoS2-metal contacts has not been well understood yet. We provide a comprehensive ab initio study of the interfacial properties of a series of monolayer (ML) and bilayer (BL) MoS2-metal contacts (metal = Sc, Ti, Ag, Pt, Ni, and Au). A comparison between the calculated and observed Schottky barrier heights (SBHs) suggests that many-electron effects are strongly suppressed in channel 2D MoS2 due to a charge transfer. The extensively adopted energy band calculation scheme fails to reproduce the observed SBHs in 2D MoS2-Sc interface. By contrast, an ab initio quantum transport device simulation better reproduces the observed SBH in 2D MoS2-Sc interface and highlights the importance of a higher level theoretical approach beyond the energy band calculation in the interface study. BL MoS2-metal contacts generally have a reduced SBH than ML MoS2-metal contacts due to the interlayer coupling and thus have a higher electron injection efficiency.

Recently, phosphorene electronic and optoelectronic prototype devices have been fabricated with various metal electrodes. We systematically explore for the first time the contact properties of monolayer (ML) phosphorene with a series of commonly used metals (Al, Ag. Cu, Au, Cr, Ni, Ti, and Pd) via both ab initio electronic structure calculations and more reliable quantum transport simulations. Strong interactions are found between all the checked metals, with the energy band structure of ML phosphorene destroyed. In terms of the quantum transport simulations, ML phosphorene forms a n-type Schottky contact with Au, Cu, Cr, Al, and Ag electrodes, with electron Schottky barrier heights (SBHs) of 0.30, 0.34, 0.37, 0.51, and 0.52 eV, respectively, and p-type Schottky contact with Ti, Ni, and Pd electrodes, with hole SBHs of 0.30, 0.26, and 0.16 eV, respectively. These results are in good agreement with available experimental data. Our findings not only provide an insight into the ML phosphorene-metal interfaces but also help in ML phosphorene based device design.

Two-dimensional (2D) semiconductors are very promising channel materials in next-generation field effect transistors (FETs) due to the enhanced gate electrostatics and smooth surface. Two new 2D materials, arsenene and antimonene (As and Sb analogues of graphene), have been fabricated very recently. Here, we provide the first investigation of the many-body effect, carrier mobility, and device performance of monolayer (ML) hexagonal arsenene and antimonene based on accurate ab initio methods. The quasi-particle band gaps of ML arsenene and antimonene by using the GW approximation are 2.47 and 2.38 eV, respectively. The optical band gaps of ML arsenene and antimonene from the GW-Bethe–Salpeter equation are 1.6 and 1.5 eV, with exciton binding energies of 0.9 and 0.8 eV, respectively. The carrier mobility is found to be considerably low in ML arsenene (21/66 cm2/V·s for electron/hole) and moderate in ML antimonene (150/510 cm2/V·s for electron/hole). In terms of the ab initio quantum transport simulations, the optimized sub-10 nm arsenene and antimonene FETs can satisfy both the low power and high performance requirements in the International Technology Roadmap for Semiconductors in the next decade. Together with the observed high stability under ambient condition, ML arsenene and antimonene are very attractive for nanoscale optoelectronic and electronic devices.

high carrier mobility, and good air stability, it has the possibility to serve as the channel material of postsilicon era. Disappointingly, most existing 2D semiconductors cannot meet these requirements simultaneously, including the most concerned 2D MoS 2 and black phosphorene (BP). [8][9][10][11][12] Experimentally, 2D MoS 2 FETs have been scaled down to the sub-10 nm region, [13][14][15] but the low on-current (<250 µA µm −1 ) mainly caused by the low carrier mobility fails to meet the International Technology Roadmap for Semiconductors (ITRS) requirements, [16] which is in accord with the results of the ab initio quantum transport simulations. [17] 2D BP FETs own high carrier mobility but are so sensitive to the air that their device performance degenerates when exposed under ambient condition. [18,19] Therefore, it is crucial to find a 2D channel material with a modest band gap, large drive current, and high air stability to continue Moore's law.Tellurium (Te), a p-type semiconductor, consists of individual helical Te chains that are stacked together by van der Waals force. [20] Recently, atomically thin tellurene (2D form of Tellurium) has been fabricated by a substrate-free solution process and molecular beam epitaxy on a graphene/6H-SiC substrate, respectively. [21][22][23] 2D tellurene possesses an anisotropic structure and is constituted of alternate tetragonal and hexagonal rings. [24,25] The band gap of tellurene monotonically decreasesThe merging 2D semiconductor tellurene (2D Group-VI tellurium) is a possible channel candidate for post-silicon field-effect transistor (FETs) due to its high carrier mobility, high drive current, and excellent air stability. The performance limits of sub-5-nm ML tellurene metal-oxide-semiconductor FETs (MOSFETs) are explored by employing exact ab initio quantum transport simulations. An optimized p-type ML tellurene MOSFET meets both the high performance (along both the armchair and the zigzag directions) and the low power (along the armchair direction) requirements of the International Technology Roadmap for Semiconductors (ITRS) at a gate length of 4 nm with a negative capacity dielectric. Hence, choosing ML tellurene as the channel material provides a novel route to continue the Moore's law to 4 nm.

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