Ultrafast dynamics of photoexcited charge carriers in nanocrystalline diamond

Abstract

We report on ultrafast charge carrier dynamics in sub-band-gap energy states in nanocrystalline diamond self-supporting membranes prepared by plasma-enhanced chemical vapor deposition technique. The obtained data are hence not influenced by the substrate effects. Results of the femtosecond transient transmission and photoluminescence laser spectroscopy indicate relaxation of photoexcited carriers with the time constants of the order of 1 ps. This is attributed to an ultrafast spatial separation of holes and electrons at the surface of nanocrystals. Only the carrier population photoexcited in energy levels of 1.68 eV silicon related center decays on a much longer time scale with the time constant of 2.4 ns.