The results show that

there is a small dispersion in stop band width for the different temperatures. Since the stop band width depends basically on the refractive index contrast that can be achieved within a cycle, it can be concluded that the anodization temperature has a small influence in the refractive index contrast. Figure 4 Evolution of central wavelength of the first stop band as function of pore-widening time for different anodization GDC-0449 supplier temperatures. Table 1 Average stop band width and corresponding standard deviation as a function of the pore-widening time Pore-widening time (min) Average stop band width (nm) Stop band width standard deviation (nm) 0 103 22 9 68 14 18 50 5 27 46 6 The average and standard deviation have been obtained for all the samples with a given pore-widening time and different temperatures. The small value of the standard deviation Selleckchem BMN-673 as compared with the average stop band width indicates that the temperature has a small influence in the refractive index contrast obtained with the cyclic voltage anodization. Conclusions In this work, we analyzed the influence of the anodization temperature and of the

number of applied voltage cycles on the photonic properties of NAA-based DBRs obtained by cyclic voltage anodization. In previous works, it was shown that DBR structures with stop bands can be obtained by the application of an anodization based in the repetition of voltage cycles between 20 and 50 V in 0.3 M oxalic acid. It was also shown that the application of a pore-widening step after anodization is crucial in order to obtain well-defined stop bands with low transmittance and high reflectance. In this work, these nanoporous structures have been obtained in the range of temperatures between 8°C and 11°C, for 50 and 150 applied voltage cycles and pore-widening times up to 27 min. The effect of these parameters

on the morphologic and photonic properties of the click here nanostructures has been studied by means of SEM and spectroscopic transmittance measurements. The results show that 50 applied voltage cycles are enough to produce stop bands and that increasing the number of cycles has two opposite effects: on one hand, dipyridamole an enhancement of the photonic stop bands is observed, in particular specially for the case of the as-produced samples, which is much better defined for samples with higher number of cycles. On the other hand, scattering losses are observed in the spectra caused by the irregular interfaces between cycles observed in the SEM images. Such losses increase with increasing number cycles and the corresponding interfaces. Increasing the anodization temperature produces a remarkable shift of the photonic stop band central wavelength, with a linear rate of 42.5 nm/°C. On the other hand, a change in anodization temperature does not influence noticeably the obtained stop band widths or the rate of the subsequent pore widening.