Single-Crystalline Metallic Films Induced by van der Waals Epitaxy on Black Phosphorus

Abstract

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 the puckered atomic structure with high chemical reactivity, and the establishment of a realistic atomic-scale picture of BP's interface toward 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 (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 forms with exceptional rotational alignment. Under a weak metal-BP interaction regime, the BP's puckered structure play 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 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.

Atomically Sharp, Closed Bilayer Phosphorene Edges by Self-Passivation

“…Its physical properties strongly depend on its crystal lattice direction. Phosphorene exhibits strong anisotropic in-plane charge transport behavior and one-dimensional diffusion on its surface. ,− Although ZZ terminations are the predominant configurations in phosphorene, − its edges have not been observed at the atomic level to a significant degree. In particular, it is difficult to image phosphorene edges because they are degraded by ambient exposure and unintended alterations to them during characterization.…”

Interface-Coupling of NiFe-LDH on Exfoliated Black Phosphorus for the High-Performance Electrocatalytic Oxygen Evolution Reaction

“…For the first time, Wang et al (2014 ) prepared the BP–Ti thin film and BP–carbon nanotube hybrid and innovatively demonstrated that BP can well drive the oxygen evolution reaction (OER). For the van der Waals layered structure of BP, the exfoliation and thickness reduction could not only effectively improve the electrical transport performance but also increase the number of active sites and improve the OER performance of BP ( Huang et al, 2019 ; Lee et al, 2021 ). Ren et al ( Ren et al, 2017 ) prepared the few-layered BP nanosheets by liquid-phase exfoliation and found that the OER onset-potential and Tafel slope of BP nanosheets were achieved at 1.45 V and 88 mV dec −1 .…”