Recently, Prof. Jing Lu's team makes big progress in the study on monolayer phosphorene−metal contacts. The results are published online in important periodical of material area “Chemistry of Materials” with the title “Monolayer Phosphorene−Metal Contacts” (DOI: 10.1021/acs.chemmater.5b04899).

Phosphorene, the youngest member of 2D materials, was mechanically exfoliated in early 2014. Monolayer and few-layer phosphorene field effect transistors have been successfully fabricated with an on−off ratio of 105 and a mobility up to 1000 cm V−1 s−1, which make phosphorene a competitive candidate channel material for nanoelectronic devices. In an actual electronic and photoelectronic device with 2D materials as the semiconducting channel, a contact with metal is usually required. In such a metal semiconductor contact, Schottky barrier is often formed at the interface, which decreases electron or hole injection efficiency and thus degrades the device performance. The formation of low-resistance metal contacts is the biggest challenge. Thus, it is necessary to find a monolayer phosphorene-metal interface with the low-resistance. It is not easy to confirm the Schottky barriers at phosphorene-metal interfaces in the transistor configuration. It is found by Prof. Lu’s team that monolayer phosphorene always underdoes a metallization under the eight metal electrodes (Al, Ag, Au, Cu, Ti, Cr, Ni, and Pd) using both ab initio electronic structure calculations and quantum transport simulations. Compared with the energy structure calculations, the quantum transport simulations are more reliable in describing SBH because of including the interactions between the metal electrodes and channel monolayer phosphorene and indeed much more consistent with the experimental results. In terms of the quantum transport simulations, n-type Schottky contacts are formed between monolayer phosphorene and Au, Cu, Cr, Al, and Ag electrodes, and p-type Schottky contacts are formed between monolayer phosphorene and Ti, Ni, and Pd electrodes. Our results are well supported by the experimental SBH data with Ni and Ti as electrodes. The further design of monolayer phosphorene electronic devices can reference our results to choose an appropriate metal electrode. In other side, the scheme including ab initio electronic structure calculations and quantum transport simulations can be extended to the confirmation of Sckottky barrier in other 2D semiconductor transistors. The first author of this work is Yuanyuan Pan, PhD student in School of Physics, Peking University. The main co-workers are Prof. Junjie Shi, Prof. Jinbo Yang, and Prof. Dapeng Yu in School of Physics, Peking University.

These works were supported by the National Natural Science Foundation of China, the National Basic Research Program of China, State Key Laboratory for Mesoscopic Physics Collaborative Innovation Center of Quantum Matter, and Hanjiang Scholar Plan.