Anodic titanium oxide photonic crystals prepared by novel cyclic anodizing with voltage versus charge modulation

Photonic crystals based on titania are of great practical importance in modern photonics owing to a variety of possibilities for their applications in optoelectronics, sensorics, and solar photovoltaics. However, the reproducible, scalable, and low-cost method of the preparation of titania photonic crystals with desired optical characteristics is still absent. Here the novel anodizing regime with voltage versus electric charge modulation, U (Q), is suggested for the precise morphology control of anodic porous films of valve metals oxides. The potential of the suggested approach is demonstrated on the preparation of high-quality one-dimensional titania photonic crystals. A new type of anodic titania nanotubes possessing periodic change of inner diameter and constant outer diameter is prepared using sine-wave modulation of applied voltage with electric charge. The possibility to tune the position of photonic band gap within the whole visible spectrum is shown.