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Changes in the porous silicon structure induced by laser radiation
Author(s) -
Salcedo Walter Jaimes,
Ramirez Fernandez Francisco J.,
Rubim Joel C.
Publication year - 2001
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.668
Subject(s) - raman spectroscopy , photoluminescence , porous silicon , laser , silicon , phonon , crystallite , raman scattering , excitation , materials science , molecular physics , analytical chemistry (journal) , chemistry , optoelectronics , condensed matter physics , optics , crystallography , physics , chromatography , quantum mechanics
Porous silicon (PS) films were investigated by Raman, and photoluminescence spectroscopies using different laser excitations at 488.0, 514.5, 632.8, and 782.0 nm. The exposure of PS layers to high laser powers causes an increase in the 480 cm −1 Raman intensity and a shift and enhancement of the PL emission. A laser‐assisted surface reaction is proposed to explain these observations. The analysis of the first‐ and second‐order Raman spectra showed that the band gaps of the PS films are indirect as in bulk c‐Si. The Raman phonon and the PL spectra and also the spectral distribution of the linear polarization degree (LPD) of PS layers were shown to be dependent on the laser excitation energy. This dependence cannot be explained within the quantum confinement model. A mechanism for the PL emission in PS layers is presented in which the radioactive recombination of electron–hole pairs occurs in localized centres (the Si—O—SiR moieties) at the pore/crystallite interface. These quasi‐molecular centres are Jahn–Teller active, i.e. the radioactive recombination is a phonon‐assisted phenomenon. Copyright © 2001 John Wiley & Sons, Ltd.