Mechanism study of self-organized TiO2 nanotube arrays by anodization

Based on analysis of the current-time curve and observation of surface morphology including top, cross-section, bottom and substrate views by scanning electron microscopy (SEM), a new growth, dissolution-breakdown model, of self-organized titania nanotube arrays is presented. By this model, many phenomena raised during anodization are explained, such as the sharp decrease of current in initial period, current transient, occurring of ridges on tube walls, and formation of not pores but tubes etc. Furthermore, the reason for the occurrence of a porous structure, the balance between internal energy and surface energy, was proposed too. This study may also shed light on the formation of porous oxide films on other valve metals.