Giant circular photogalvanic effect of the surface states in an ultra-thin Bi2Se3 nanoplate grown by chemical vapor deposition

Abstract

Ultra-thin Bi2Se3 nanoplates with high crystal quality are obtained by chemical vapor deposition (CVD). A giant circular photogalvanic effect (CPGE) has been observed in the ultra-thin Bi2Se3 nanoplates, which is about one order larger than that previously observed in the thick Bi2Se3 nanoplates grown by CVD and that in the thin Bi2Se3 film grown by molecular beam epitaxy. By applying an ionic liquid gate, the CPGE can be effectively tuned. As the gate voltage increases, the magnitude of the CPGE current decreases, suggesting that the CPGE current under zero gate voltage is dominated by surface states rather than the two-dimensional electron gas (2DEG). It is revealed that as the surface roughness of the Bi2Se3 nanoplates increases, the CPGE decreases and finally reverses the sign, indicating the dominant contribution of the CPGE switches from the top surface states to the 2DEG or the bottom surface states.