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Time‐resolved ultrafast carrier dynamics in as‐grown nanocrystalline silicon films: the effect of film thickness and grain boundaries
Author(s) -
Lioudakis Emmanouil,
Othonos Andreas
Publication year - 2008
Publication title -
physica status solidi (rrl) – rapid research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.786
H-Index - 68
eISSN - 1862-6270
pISSN - 1862-6254
DOI - 10.1002/pssr.200701219
Subject(s) - nanocrystalline material , materials science , grain boundary , relaxation (psychology) , brillouin zone , ultrashort pulse , silicon , condensed matter physics , ultrafast laser spectroscopy , nanocrystalline silicon , chemical physics , optoelectronics , optics , nanotechnology , chemistry , crystalline silicon , composite material , amorphous silicon , laser , physics , psychology , social psychology , microstructure
In this letter, we have studied transient photoinduced absorption in as‐grown nanocrystalline silicon films with thickness varied from 5 to 30 nm. Effects of quantum confinement (QC) in z ‐direction and grain boundary distortions alter the carrier dynamics of these films considerably. Based on the determination of critical points in the first Brillouin zone of the band structure of materials, we have time‐resolved the relaxation times of surface‐related states and indirect valleys. When decreasing the film thickness down to the QC limit (∼10 nm) new ultrafast relaxation mechanisms start to play a dominant role in carrier dynamics due to the topological disordering of these ultrathin films. These relaxation mechanisms seem to be related with the traping/de‐traping of the excited carriers prior to recombination. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)