Salt-Assisted Low-Temperature Growth of 2D Bi 2 O 2 Se with Controlled Thickness for Electronics.

Bi 2 O 2 Se is the most promising 2D material due to its semiconducting feature and high mobility, making it propitious channel material for high-performance electronics that demands highly crystalline Bi 2 O 2 Se at low-growth temperature. Here, a low-temperature salt-assisted chemical vapor deposition approach for growing single-domain Bi 2 O 2 Se on a millimeter scale with thicknesses of multilayer to monolayer is presented. Because of the advantage of thickness-dependent growth, systematical scrutiny of layer-dependent Raman spectroscopy of Bi 2 O 2 Se from monolayer to bulk is investigated, revealing a redshift of the A 1g mode at 162.4 cm -1 . Moreover, the long-term environmental stability of ≈2.4 nm thick Bi 2 O 2 Se is confirmed after exposing the sample for 1.5 years to air. The backgated field effect transistor (FET) based on a few-layered Bi 2 O 2 Se flake represents decent carrier mobility (≈287 cm 2  V -1 s -1 ) and an ON/OFF ratio of up to 10 7 . This report indicates a technique to grow large-domain thickness controlled Bi 2 O 2 Se single crystals for electronics.