Electronic Structures and Lattice Dynamics of Layered BiOCl Single Crystals

BiOCl has recently elicited intense interest for its excellent photochemical catalysis, energy conversion, and photodetection performance. In this Letter, we systematically investigate BiOCl electronic properties, lattice dynamics, and structural stability. From first-principles calculations, bulk and monolayer BiOCl have ultraviolet indirect band gaps around 3.6 eV, consistent with reflection spectroscopy measurements. The large spin-orbit coupling effect of the Bi atom makes the lowest conduction band near the Z point in the Brillouin region move down 230 meV. However, because of the symmetrical crystal potential, BiOCl has no strong Rashba effect. We further observed all 6 BiOCl Raman-active modes with the lowest-frequency rigid layer in-plane vibrational mode at 63 cm^-1, consistent with our calculations. Up to 500 K or down to monolayer thickness, the crystal structure of BiOCl remains stable. Our work provides detailed information on BiOCl electronic and vibrational properties and stability up to high temperature or down to monolayer, identifying it as a promising layered material for further nano-optoelectronic applications.