Optical Properties and Applications of Multilayer Systems of Thin Metal Films with Nanometer Hole Arrays on Porous Alumina - Aluminum Substrate

Juris Prikulis Institute of Chemical Physics, University of Latvia, Riga, Latvia Tomas Tamulevičius Institute of Chemical Physics, University of Latvia, Riga, Latvia Raimonds Poplausks Institute of Chemical Physics, University of Latvia, Riga, Latvia Gatis Bergs Institute of Chemical Physics, University of Latvia, Riga, Latvia Indra Apsite Institute of Chemical Physics, University of Latvia, Riga, Latvia Uldis Malinovskis Institute of Chemical Physics, University of Latvia, Riga, Latvia Donats Erts Institute of Chemical Physics, University of Latvia, Riga, Latvia

Recently metal coated porous anodized aluminum oxide (AAO) layers have attracted interest for potential optical filtering or sensor applications. The colorful appearance of these coatings is mainly governed by interference effects between the semitransparent thin metal film and reflection from aluminum surface. This simplified interference model largely neglects the role of holes in metal layers, which however, can significantly change the spectral properties [1] and are of great importance e.g. for surface enhanced Raman spectroscopy [2].

We addresses the optical properties of 10-35 nm thin metal films with 18-25 nm diameter holes obtained by deposition of gold or silver on 75-280 nm layers of AAO supported by bulk aluminum substrate. We show a comprehensive study of these multilayer systems including spectroscopic ellipsometry measurements and demonstrate how various system parameters influence the optical response. Apart from interference related minima and maxima, which shift with change of AAO thickness we observe optical attenuation components which fall out of regular pattern and are metal material dependent.

We also demonstrate several applications of these multilayer systems where simple optical measurements can be used to extract e.g. information about metallurgical structure of aluminum or refractive index sensing.

Support from the ESF project 1DP/1.1.1.2.0/13/APIA/VIAA/054 is gratefully acknowledged.

References

[1] Masuda, H., & Fukuda, K. (1995). Ordered metal nanohole arrays made by a two-step replication of honeycomb structures of anodic alumina. Science, 268(5216), 1466–8. doi:10.1126/science.268.5216.1466

[2] Choi, D., Choi, Y., Hong, S., Kang, T., & Lee, L. P. (2010). Self-organized hexagonal-nanopore SERS array. Small, 6(16), 1741–4. doi:10.1002/smll.200901937

juris.prikulis@lu.lv