Femtosecond Photoexcited Carrier Dynamics in Reduced Graphene Oxide Suspensions and Films

TL;DR

This study investigates ultrafast carrier relaxation dynamics in reduced graphene oxide, revealing three distinct timescales and differences between suspensions and films, with implications for optoelectronic applications.

Contribution

It provides detailed measurements of femtosecond carrier dynamics in reduced graphene oxide, highlighting differences between suspensions and films and estimating nonlinear susceptibility.

Findings

Carrier relaxation occurs in three distinct timescales: ~200 fs, 1-2 ps, and ~25 ps.

The hot optical phonon lifetime (1-2 ps) is larger in suspensions than in films.

Third order nonlinear susceptibility is quantified and compared with Z-scan results.

Abstract

We report ultrafast response of femtosecond photoexcited carriers in single layer reduced graphene oxide flakes suspended in water as well as few layer thick film deposited on indium tin oxide coated glass plate using pump-probe differential transmission spectroscopy at 790 nm. The carrier relaxation dynamics has three components: ~200 fs, 1 to 2 ps, and ~25 ps, all of them independent of pump fluence. It is seen that the second component (1 to 2 ps) assigned to the lifetime of hot optical phonons is larger for graphene in suspensions whereas other two time constants are the same for both the suspension and the film. The value of third order nonlinear susceptibility estimated from the pump-probe experiments is compared with that obtained from the open aperture Z-scan results for the suspension.