Polarization-enhanced cell walls etching of anodic titanium oxide

Abstract

Anodic titanium oxide (ATO) photonic crystals (PhCs) are promising for photonics, photocatalysis, and solar cells. A refractive index modulation in ATO PhCs is caused by the modulation of porosity and, thus, the pore diameter should be controlled precisely. The ATO cell walls etching in electrolyte solution during anodizing increases the porosity of the PhC structure and shifts the photonic band gap (PBG) position to shorter wavelengths. Until now, the ATO cell walls etching in organic based electrolytes has been associated solely with the chemical dissolution of ATO in fluoride-containing solutions. Here, a significant enhancement of cell walls etching is observed when electric current flows under anodic polarization. This effect leads to the blue shift of the PBG position with the number of periods of ATO PhC structure. Therefore, it is essential for the synthesis of ATO PhCs with a precise PBG position.

One-Dimensional Photonic Crystals with Nonbranched Pores Prepared via Phosphorous Acid Anodizing of Aluminium

“…Photonic crystals (PhCs) are structured materials that possess photonic band gapswavelength bands in the optical range, where light reflects on the periodic structure due to Bragg diffraction [1][2][3]. Valve metals' anodizing under periodically oscillating conditions is a low-cost, scalable, and reproducible method of preparing one-dimensional (1D) PhCs [4][5][6][7][8][9][10]. PhCs based on anodic aluminium oxide (AAO) are used in chemical sensors [5,[11][12][13][14], low-threshold lasers [15,16], optical filters [17,18], photonic tags [19], and photocatalysis [20,21].…”

Stained Glass Effect in Anodic Aluminum Oxide Formed in Selenic Acid

“…The extrema observed in the wavelength range 720–920 nm of spectra measured under incident angles of 0–45° were analyzed. The fitting parameters included two Cauchy dispersion parameters, the film thickness, and the order of interference of a certain extremum. − …”

“…Figure c shows the profiles of the PhC thickness ( h PhC ), n eff , and λ PBG measured using spectroscopy along the white arrows indicated in Figure . The values of h PhC and n eff were obtained by the analysis of the Fabry–Pérot optical interference fringes at different incident angles. ,− The difference in the thickness of the PhC (Δ h PhC ) formed on grains 1 and 2 obtained by profilometry and by the analysis of the Fabry–Pérot optical interference fringes was 1.65 and 1.70 μm, respectively. The convergence of the results obtained by independent methods confirms the accuracy of the performed measurements.…”