Vapor-Liquid-Solid Growth of Bi2O2Se Nanoribbons for High-Performance Transistors

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 mu m 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 similar to 220 cm(2).V-1.s(-1) at room temperature, good switching behavior with on/off ratio of >10(6), and high on current density of similar to 42 mu A.mu m(-1) at a channel length of 10 mu m. Therefore, Bi2O2Se nanoribbons are expected to be a promising materials for building high-performance transistors in the future.