Laser-induced periodic surface structures, also known as ripples, have been investigated for a long time on various materials. They are self-organized grating-like structures that form spontaneously upon irradiation with a single laser beam; their formation requiring a high temperature rise, it generally results from interactions with ultrashort laser pulses. Recently, similar phenomena leading to periodic changes in the morphology of metallic nanoparticles embedded in polymer films have been reported under femtosecond laser exposure. Here, we demonstrate that chain-like self-organized silver nanoparticles can be grown, from an ionic silver precursor, within titania films under continuous wave visible laser beam. The nanoparticle chains are periodically spaced with a period that depends on the wavelength and are oriented parallel to the laser polarization. The samples present no significant surface modulation since all of the grown nanoparticles are located at the substrate-film interface, protected by a crystallized TiO₂ film. SEM, TEM, HRTEM and EDX characterizations of the film nanostructuring are shown. Due to the coupling of incident light to a guided mode of the TiO₂ film by the first diffraction order of the NP grating, such samples exhibit a strong dichroism whose characteristics depend on the laser exposure conditions. Color changes and spectral variations with polarization are measured and interpreted. The high stability of such colored films under high temperature rises or high intensity UV or visible exposures is demonstrated; it makes them good candidates for colored data storage.

Date Published: 22 February 2013
PDF: 7 pages
Proc. SPIE 8609, Synthesis and Photonics of Nanoscale Materials X, 860905 (22 February 2013); doi: 10.1117/12.2003178

Published in SPIE Proceedings Vol. 8609:
Synthesis and Photonics of Nanoscale Materials X
Jan J. Dubowski; David B. Geohegan; Frank Träger, Editor(s)