Ultrafast time-resolved spectroscopy of In2 O3 nanowires

Abstract

Ultrafast carrier dynamics in In2 O3 nanowires with an average diameter of ≈100±20 nm grown by the vapor-liquid-solid method have been investigated in detail using differential absorption spectroscopy with femtosecond resolution. Measurements revealed that state filling is important for states above the band gap and states just below the band edge, thus demonstrating the critical role that shallow traps play in the relaxation of the photogenerated carriers. Furthermore, time-resolved intensity measurements revealed the importance of Auger recombination in the relaxation of carriers in the In2 O3 nanowires and provided the maximum fluence (∼3 μJ/ cm2) where this recombination mechanism may be considered negligible. Transient measurements in this low-fluence regime for carriers above the band gap revealed single exponential recovery (∼1.5 ns) associated with recombination of the photogenerated carriers. Similar behavior has been observed for the photogenerated carriers distributed within the shallow traps just below the band edge. Furthermore, measurements at longer probing wavelengths provided an estimate of the nonradiative relaxation of carriers (∼300 ps), which are distributed among the midgap states. Finally, long-lived oscillations in the transient reflection were detected, which corresponds to the presence of longitudinal acoustic phonons in the In 2 O3 nanowires. © 2009 American Institute of Physics.