| 초록 |
Carrier injection in wide-band-gap materials is attracting a considerable research interest due to its potential applications in hot carrier solar cells, photocatalysis, next generation of ultrafast nanophotonics, etc. However, despite experimental and theoretical investigations, the dynamics of hot carrier injection at nanoscale is still missing. Herein, we demonstrate the tunneling dynamics of hot carriers in ZnO/Al2O3/silver-nanowires (Ag-NWs) heterostructures via Al2O3 layer, revealed by nanoscale current maps and bulk current-voltage measurements. The optical properties of the device were measured by transmittance and absorbance measurements. In addition, the effect of thickness of tunneling layer (Al2O3 films) on the electrical and optical properties of the ZnO-covered Ag-NWs structures was investigated. Further, electrostatic force microscopy (EFM) has employed to understand the direct charge transfer through tunneling from Ag-NWs to the ZnO layer. The generation of the photocurrent is also confirmed using low-energy photons in ZnO/Al2O3/Ag-NWs heterostructures whereas no photocurrent was observed in ZnO/Ag-NWs heterostructures. Furthermore, surface electric potential characteristics are measured to examine additional details about charge transfer in the films using Kelvin probe force microscopy (KPFM). The femtosecond pump-probe transient absorption measurements also confirm the transfer of carrier from Ag-NWs to ZnO layer. Thus, the Ag-NWs-covered by ZnO/Al2O3 heterostructures pave a simple way to enhance the carrier injection in photovoltaics and photocatalysis applications. |
