Controlled Synthesis of High-Mobility Atomically Thin Bismuth Oxyselenide Crystals

Non-neutral layered crystals, another group of two-dimensional (2D) materials that lack a well-defined van der Waals (vdWs) gap, are those that form strong chemical bonds in-plane but display weak out-of-plane electrostatic interactions, exhibiting intriguing properties for the bulk counterpart. However, investigation of the properties of their atomically thin counterpart are very rare presumably due to the absence of efficient ways to achieve large-area high-quality 2D crystals. Here, high-mobility atomically thin Bi2O2Se, a typical non-neutral layered crystal without a standard vdWs gap, was synthesized via a facial chemical vapor deposition (CVD) method, showing excellent controllability for thickness, domain size, nucleation site, and crystal-phase evolution. Atomically thin, large single crystals of Bi2O2Se with lateral size up to similar to 200 mu m and thickness down to a bilayer were obtained. Moreover, optical and electrical properties of the CVD-grown 2D Bi2O2Se crystals were investigated, displaying a size-tunable band gap upon thinning and an ultrahigh Hall mobility of >20000 cm(2) V-1 s(-1) at 2 K. Our results on the high-mobility 2D Bi2O2Se semiconductor may activate the synthesis and related fundamental research of other non-neutral 2D materials.National Natural Science Foundation of China [21525310]; National Basic Research Program of China [2014CB932500]; National Program for Support of Top-Notch Young ProfessionalsSCI(E)ARTICLE53021-30261