Investigation of Photoexcited Carrier Dynamics in Hematite and the Effect of Surface Modifications by an Advanced Transient Grating Technique

摘要

Photoexcited carrier dynamics in a hematite film with and without amorphous NiFeO_(x) on the surface was investigated using the heterodyne transient grating method. We found that two different electron/hole dynamics took place in the micro- and millisecond time regions and successfully assigned each component to the decay processes of electrons and holes trapped at surface states, respectively. It was also demonstrated that the amorphous NiFeO_(x) coating plays a crucial role in increasing the survival of the holes at the surface trap states, which was caused by the decrease in the surface recombination rate.