Evidence of photoinduced charge transfer in C-60/GaAs(100) bilayers by pump-probe measurements

Hybrid interfaces in semiconductor heterostructures consisting of C-60/GaAs bilayers have been investigated by means of ultrafast pump-probe spectroscopy. From previous results, the energy levels alignment at the interface shows no injection barrier for electrons from GaAs to C-60. Measurements have been carried out in order to monitor photoinduced electron transfer across the interface. Upon selective excitation of the GaAs layer we observe photobleaching (PB) of C-60 due to a decrease of C-60 neutral molecules. We monitor the PB dynamics concluding that electron transfer proceeds in about 4 ps and then relaxes back to ground state in timescales beyond 100 ps. (C) 2008 Elsevier B.V. All rights reserved.