Optical and structural characterization of nanostructured Alq3 with negative in-plane birefringence

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In this study, we investigate the optical and structural properties of tilted columnar thin films composed of Alq3 in order to better understand the source of the in-plane birefringence exhibited by such films which is critical in designing and modelling nanostructured devices incorporating porous architectures such as photonic crystals (ie: square spiral structure), rugate filters, and polarized light emitting devices. Previous work done on chiral Alq3 films have demonstrated a notable absence of column broadening and secondary structural anisotropy (asymmetric fanning of columns) commonly observed in inorganic films. In addition, strong chiral optical behaviour is observed in Alq3 helical films dependent on the deposition angle. The magnitude of circular Bragg reflection (preferential reflection of one handedness of circular polarized light) of chiral thin films is related to the in-plane birefringence. This suggests that the in-plane birefringence of tilted columnar Alq3 films drives such behaviour and should increase with the deposition angle. This trend is contrary to the one observed in tilted columnar inorganic thin films which exhibit peak values of in-plane birefringence at deposition angles 60° < alpha < 70°.Variable angle spectroscopic ellipsometry, scanning electron microscopy, and the Bruggeman effective medium approximation description was used to characterized the films.

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Journal: TechConnect Briefs
Volume: 1, Technical Proceedings of the 2007 NSTI Nanotechnology Conference and Trade Show, Volume 1
Published: May 20, 2007
Pages: 320 - 323
Industry sector: Advanced Materials & Manufacturing
Topic: Advanced Materials for Engineering Applications
ISBN: 1-4200-6182-8