关键词: Bi₂O₂Se, 气-液-固生长, 纳米带, 化学气相沉积, 高迁移率

Abstract:

Nanostructured bismuth oxyselenide (Bi₂O₂Se) semiconductor, a two-dimensional (2D) materials with high-mobility, air-stability, and tunable bandgap, has recently emerged as a candidate of channel material for future digital (electronic and optoelectronic) applications. In terms of material morphology, some basic issues will be addressed when a two-dimensional layered crystal is shaped into a one-dimensional (1D) geometry due to size effect; these include the space-confined transport in a plane, which leads to dramatic changes in electronic, optical, and thermal properties. These novel 1D nanostructures with unique properties are an optimal choice for fabricating next-generation integrated circuits and functional devices within the nanometer scale such as gate-all-around field-effect transistors, single-electron transistors, chemical sensors, and THz detectors. As one of the high-mobility 2D semiconductor, 1D high-quality Bi₂O₂Se nanoribbons could be promising for applications in high-performance transistors; however, their synthesis has not been completely developed yet. In our study, we report on the facile growth of Bi₂O₂Se nanoribbons on mica substrates via a bismuth-catalyzed vapor-liquid-solid (VLS) mechanism. The preparation of Bi₂O₂Se nanoribbons is based on a previous work that emphasized on the oxidation of Bi₂Se₃ in a chemical vapor deposition (CVD) system and the use of bismuth (Bi) particles as the precursor of Bi catalysis. The morphology, composition, and structure of the as-grown Bi₂O₂Se nanoribbons were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, transmission electron microscopy (TEM), as well as other methods. For a Bi mediated VLS growth process, the growth of Bi₂O₂Se nanoribbons can be self-assembled; further, in this process, as-grown epitaxial Bi₂O₂Se nanoribbons are free-standing with out-of-plane morphology on the mica substrate. Additionally, combining the spherical aberration corrected transmission electron microscope (ACTEM) and selected electron diffraction (SAED) methods, we discovered that the as-synthesized Bi₂O₂Se nanoribbons were single crystalline with high quality. We further investigated the controllable growth for domain size by optimizing the growth temperature of the Bi₂O₂Se nanoribbons. As-synthesized single-crystal Bi₂O₂Se nanoribbons have widths in the range of 100 nm to 20 μm and lengths in the sub-millimeter range. By employing a polymer poly(methyl methacrylate) (PMMA) assisted clean transfer method with the assistance of deionized water, the Bi₂O₂Se nanoribbons can be easily transferred onto a SiO₂/Si substrate. Fabricated into the top-gated field-effect device, the Bi₂O₂Se nanoribbon sample (transferred to the SiO₂/Si substrate) exhibited high electronic performances; these included a high electron mobility of ∼220 cm²∙V⁻¹∙s⁻¹ at room temperature, good switching behavior with on/off ratio of > 10⁶, and high on current density of ∼42 μA∙μm⁻¹ at a channel length of 10 μm. Therefore, Bi₂O₂Se nanoribbons are expected to be a promising materials for building high-performance transistors in the future.

Key words: Bismuth oxyselenide, Vapor-liquid-solid growth, Nanoribbons, CVD, High mobility