The properties of metal-semiconductor junctions are often unpredictable because of non-ideal interfacial structures, such as interfacial defects or chemical reactions introduced at junctions. Black phosphorus (BP), an elemental two-dimensional (2D) semiconducting crystal, possesses a puckered atomic structure with high chemical reactivity, and the establishment of a realistic atomic-scale picture of BP's interface toward the metallic contact has remained elusive. Here, we examine the interfacial structures and properties of physically deposited metals of various kinds on BP. We find that Au, Ag, and Bi form single-crystalline films with a (110) orientation through guided van der Waals epitaxy. Transmission electron microscopy and X-ray photoelectron spectroscopy confirm that atomically sharp van der Waals metal-BP interfaces are formed with an exceptional rotational alignment. Under a weak metal-BP interaction regime, BP's puckered structure plays an essential role in the adatom assembly process and can lead to the formation of a single crystal, which is supported by our theoretical analysis and calculations. The experimental survey also demonstrates that the BP-metal junctions can exhibit various types of interfacial structures depending on metals, such as the formation of a polycrystalline microstructure or metal phosphides. This study provides a guideline for obtaining a realistic view on metal-2D semiconductor interfacial structures, especially for atomically puckered 2D crystals.
Bibliographical noteFunding Information:
We are grateful to Yeonjin Yi and Hyunbok Lee for helpful discussion. This work was mainly supported by the Basic Science Research Program at the National Research Foundation of Korea (NRF-2017R1A5A1014862 and NRF-2019R1C1C1003643), by the Yonsei Signature Research Cluster Program of 2021 (2021-22-0004), and by the Institute for Basic Science (IBS-R026-D1). Y.L. received support from the Basic Science Research Program at the National Research Foundation of Korea which was funded by the Ministry of Education (NRF-2020R1A6A3A13060549), Ministry of Science and ICT (NRF-2021R1C1C2006785), and from the 2020 Yonsei University Graduate School Research Scholarship Grants. H.-g.K. and H.J.C. are supported by the NRF of Korea (grant no. 2020R1A2C3013673). Computational resources have been provided by the KISTI Supercomputing Center (project no. KSC-2019-CRE-0195). H.Y.J. acknowledges the support from the Basic Science Research Program at the National Research Foundation of Korea (NRF-2018R1A2B6008104). G.H.L. acknowledges the support from the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (20173010013340), and the Creative-Pioneering Researchers Program through Seoul National University (SNU).
© 2021 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Materials Chemistry