Heterointerface-enhanced ultrafast carrier dynamics and nonlinear optical response via constructing electronic structure-induced type-I ZnO-MoS2 n-n heterojunction

Here, ZnO, MoS2 films and ZnO nanoparticles-coated MoS2 (ZMO) heterojunction were successfully prepared based on spontaneous and non-spontaneous nucleation processes, which exhibited ultrafast carrier dynamics for optoelectronic devices surpassing the limitations of single-semiconductor optical modulator where the heterointerface effect extend the response time into the sub-femtosecond regime. The controllable morphology and polar growth state at heterointerface can be confirmed by scanning/transmission electron microscopy. The linear absorption and transmittance of MoS2 base film in ZMO heterojunction were measured by finite difference time domain method and UV–Vis spectrophotometer, which concluded the significant light-material interaction. The enhanced inter-band emission and Raman peak A1g of ZMO were slightly shifted, which means the successful formation of electron transfer process among the heterointerface. Subsequently, the valence band and conduction band offset of the ZMO heterojunction were determined using the Zn 2p3/2 and Mo 3d3/2 core levels. The multi-stage relaxation process caused by the built-in electric field of heterointerface was determined. The ZMO heterojunction with excellent nonlinear absorption (NLA) coefficient (10-3 ∼ 10-5 cm/W) was 10 ∼ 1000 times higher than that of pure materials. The type-I ZMO n-n heterojunction caused by controllable electronic structure with ultrafast NLA behavior, which can provide application strategies in all-optical switching devices.