Table of Contents
Research Letters in Physics
Volume 2008, Article ID 837503, 5 pages
http://dx.doi.org/10.1155/2008/837503
Research Letter

Observation of Quantum Confinement Effects with Ultrashort Excitation in the Vicinity of Direct Critical Points in Silicon Nanofilms

Research Center of Ultrafast Science, Department of Physics, University of Cyprus, P.O. Box 20537, Nicosia 1678, Cyprus

Received 1 March 2008; Accepted 7 April 2008

Academic Editor: Lorenzo Pavesi

Copyright © 2008 Andreas Othonos et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We report on the observation of quantum confinement effects and the influence of surface-related states due to the formation of nanograins on ultrashort relaxation near the direct critical points of silicon nanofilms following UV-excitation. Direct photoexcitation of the samples in the vicinity of the Γ critical points of the first Brillouin zone has been achieved using femtosecond pulses in the spectra range of 290–400 nm. Transient absorption measurements show a substantial enhancement of state filling with decreasing the film thickness down to 5 nm due to quantum confinement in the z-direction. Furthermore, the state filling of surface-related states of nanograins suggests that the critical points of these states follow the ellipsometry extracted energy-curve.