Abstract
The influence of the anodization temperature and of the number of applied voltage cycles on the photonic properties of nanoporous anodic alumina-based distributed-Bragg reflectors obtained by cyclic voltage anodization is analyzed. Furthermore, the possibility of tuning the stop band central wavelength with a pore-widening treatment after anodization and its combined effect with temperature has been studied by means of scanning electron microscopy and spectroscopic transmittance measurements. The spectra for samples measured right after anodization show irregular stop bands, which become better defined with the pore widening process. The results show that with 50 applied voltage cycles, stop bands are obtained and that increasing the number of cycles contributes to enhancing the photonic stop bands (specially for the case of the as-produced samples) but at the expense of increased scattering losses. The anodization temperature is a crucial factor in the tuning of the photonic stop bands, with a linear rate of 42 nm/°C. The pore widening permits further tuning to reach stop bands with central wavelengths as low as 500 nm. Furthermore, the results also show that applying different anodization temperatures does not have a great influence in the pore-widening rate or in the photonic stop band width.
Highlights
Nanoporous anodic alumina (NAA) is a material of great interest in nanotechnology because of its cost-effective and up-scalable production techniques [1,2,3] and because of its vast field of applications [4,5,6,7,8]
NAA-based distributed-Bragg reflector (DBR) can be achieved by taking advantage of the fact that a wet etching applied after the anodization to enlarge the pore diameter has a different rate depending on the used anodization voltage [23]
We study the influence of the number of cycles and of the anodization temperature on the optical properties of NAA-based DBR
Summary
Nanoporous anodic alumina (NAA) is a material of great interest in nanotechnology because of its cost-effective and up-scalable production techniques [1,2,3] and because of its vast field of applications [4,5,6,7,8]. This material consists of an array of cylindrical pores in an aluminum oxide matrix obtained by electrochemical anodization of aluminum. Other authors have reported on the fabrication of DBR structures by applying a cyclic anodization voltage [19,20,24] they did not stress the importance of the pore-widening step in order to obtain the photonic stop bands
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