Charge transport and localization in nanocrystalline CdS films: A time-resolved terahertz spectroscopy study

0361370 - FZÚ 2012 RIV US eng J - Journal Article
Mics, Zoltan - Němec, Hynek - Rychetský, Ivan - Kužel, Petr - Formánek, P. - Malý, P. - Němec, P.
Charge transport and localization in nanocrystalline CdS films: A time-resolved terahertz spectroscopy study.
Physical Review. B. Roč. 83, č. 15 (2011), "155326-1"-"155326-6". ISSN 1098-0121
R&D Projects: GA ČR GD202/09/H041; GA ČR(CZ) GP202/09/P099; GA ČR GA202/09/0430; GA MŠMT LC512; GA AV ČR(CZ) IAA100100902
Institutional research plan: CEZ:AV0Z10100520
Keywords : time-resolved THz spectroscopy * CdS nanoparticles * electron transport * chemical bath deposition
Subject RIV: BM - Solid Matter Physics ; Magnetism
Impact factor: 3.691, year: 2011

Assessment of characteristic length and time scales of the charge localization in nanostructured semiconductors is a key point for understanding the initial stage of carrier transport after photoexcitation. A use of time-resolved terahertz spectroscopy and Monte Carlo simulations of the electron motion allow us to obtain this information and develop a microscopic model of the electron transport in a nanocrystalline CdS film. A weak localization is observed inside individual nanocrystals (NCs) while much stronger localization stems from the existence of NC clusters. The efficiency of the short-range transport is controlled by the excess energy of electrons: Its increase enhances the conductive coupling between adjacent NCs and clusters. Relaxation of electrons with high excess energy then leads to a decrease of their mobility on a sub-ps time scale. Filling of conduction-band states by increasing the optical pump fluence allows us to maintain a high mobility even at later times.
Permanent Link: http://hdl.handle.net/11104/0198694