Preparation of titanium oxide pillars on glass substrates and ultrathin titanium oxide layer using PMMA/PS blend films

In this paper, a simple and inexpensive method of preparing nanosized titanium oxide (TiO2) pillars on glass substrates and ultrathin TiO2 layers is presented, utilizing a blend of commercially available polystyrene (PS) and poly(methyl methacrylate) (PMMA). The surface morphology of PS/PMMA blend films is investigated in terms of the processing parameters including solution concentration, blending ratio, and spin-coating speed. For the first time, a phase inversion was revealed for the PS/PMMA blend films spun coated on conducting substrates (ITO and TiO2) with increasing solution concentration. Atomic force microscopy studies show that PMMA forms vertical cylindrical structures in the matrix of PS on glass substrates and on ultrathin TiO2 layers deposited on indium tin oxide (ITO) substrates. After the PMMA phase is etched away by ultraviolet irradiation and acetic acid, TiO2 pillar structures are successfully created on both types of substrates by infiltration of the sol-gel mixture into the nanosized PS templates followed by calcination at an elevated temperature. The size and shape of the TiO2 Pillars were found to be affected by the thickness and phase separation of the initial PS/PMMA films, which depend on the solution concentration and blending ratio of the two polymeric components.