Berlin 2008 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 52: Symposium Semiconducting Nanoparticles for Nano-Optics and Optoelectronics

HL 52.5: Invited Talk

Friday, February 29, 2008, 12:30–13:00, ER 270

Ultrafast Exciton Relaxation Dynamics in Silicon Quantum Dots — •Carola Kryschi, Volker Kuntermann, Carla Cimpean, Vincent Groenewegen, and Anja Sommer — Institut für Physikalische Chemie I, FAU, Egerlandstr. 3, D-91058 Erlangen

A fundamental objective in nanoelectronics is to understand and to control electron flow between semiconductor nanoparticles which is mediated by chromophores attached to the nanoparticle surfaces. Our research activities are directed to the development of silicon quantum dots (Si qdots)with optical and electronic properties which may be adjusted by strong electronic interactions with suited chromophores. Therefore Si qdots with covalently bound chromophores were prepared which exhibit photoluminescence (PL) in the visible with quantum yields up to 37 %. The spectral features of the PL were observed to strongly depend on both, the quantum dot size and the conjugation of the electron system of the chromophores. In order to elucidate the electronic interactions between chromophore states and Si bulk states the PL properties of Si qdots dispersions were examined conducting stationary and time-resolved PL spectroscopy experiments, while ultrafast exciton rise and decay dynamics were studied using femtosecond transient absorption spectroscopy. A pyridine based chromophore was observed to provide nearly resonant electronic interactions with bulk states, whereas the temporal evolution of the transient absorption spectra obtained from a thiophene based chromophore gave unambiguous indication of excitation energy transfer from the chromophore to the Si bulk.