Group V materials: From bulk to monolayer

Abstract

Since graphene has been fabricated successfully in 2004, two dimensional (2D) materials have received a great attention because of their exceptional properties and novel applications. However, there are problems exist in traditional 2D materials. Graphene, as the very first 2D material, is a zero band-gap semiconductor which results in low on-off ratio. Hexagonal boron nitride (hBN) has a large band-gap around 6 eV that can be considered as insulator. Monolayer MoS2 also is an important 2D material, but the relative low mobility limits its applications. In 2014, few and single layer black phosphorus (BP) was achieved by mechanical exfoliation. And p-type field effect transistors (FETs) based on few-layer phosphorene also have been fabricated successfully. The BP FETs exhibit high mobility value up to ~1000 cm2/(V s) at room temperature. Besides, a direct band-gap of ~2 eV indicates that monolayer BP possess a high on/off ratio. These two advantages make phosphorene a promising FET material which is the most desirable application of 2D materials. Despite the superior properties, phosphorene still has its problems. When exposure to air, phosphorene tends to degradation and breakdown which restrict their applications in electronic and optoelectronic devices. The production of monolayer BP provokes wondering if other elements from group V can be the potential elemental 2D crystals. Elements from group V beyond phosphorus should be more chemical steady than phosphorus. And like black phosphorus, grey arsenic, grey antimony and rhombohedral bismuth are the most stable phase of these three elements with layer structures. For these two reasons, there are many reports about arsenic, antimony and bismuth in 2D structures. In this paper, we review the development of group V elemental materials from three-dimensional (3D) to 2D. Bulk arsenic and antimony are narrow semiconductor and semimetal, respectively. Differ from black phosphorus with orthorhombic structure, grey arsenic and grey antimony possess rhombohedral structures. Through density functional theory (DFT) calculation, the phonon spectra proved the thermodynamics stabilities of monolayer As and Sb. And an intriguing indirect-to-direct band-gap transition at a relatively small critical strain has been reported. After that, a lot of properties of group V elemental 2D materials are reported. Theoretically, their properties can be manipulated by functionalization, strain and electric field to applying magnetic, electronic, topological and thermoelectrical materials. Experimentally, arsenene and antimonene can be produced via liquid exfoliation, van der Waals epitaxy, mechanical exfoliation, plasma-assisted process and molecular beam epitaxy. Based on the antimonene fabricated by liquid exfoliation, an unexpected nonlinear optical limiting property which is even better than graphene in the visible and near infrared region (532–2000 nm) and high transmission (more than 80%) when dispersed in solutions or high concentration doped in Ormosil gel glasses. This might lead to many promising applications in nonlinear optical fields such as laser protection.