Fabrication of TiO2 nanodot films using simple solution dipping method and block copolymer template

Abstract

Block copolymer (BCP) self-assembled nanostructures as a template in conjunction with a low-cost inorganic material deposition method can be a practical solution for many applications in the fields of microelectronics, optoelectronics, and plasmonics. Here, we demonstrate the fabrication of TiO2 nanodot films using polystyrene-b-polymethylmethacrylate (PS-b-PMMA) BCP as a template and a simple solution dipping process for TiO2 deposition. For this purpose, we prepared BCP templates using two different methods, namely, the selective deposition method and the masked deposition method. In the selective deposition method, as-grown self-assembled cylinder forming PS-b-PMMA was used as a template and in the masked deposition method, PMMA was etched out selectively from PS-b-PMMA nanostructured films. The scanning electron microscopy results show the average diameter of TiO2 nanodots grown by the selective deposition method is smaller compared to the masked deposition method, whereas the inter-nanodot distance is similar for both deposition methods. X-ray diffraction and photoluminescence confirm the formation of TiO2 in samples deposited by these two methods. The smaller nanodot size for the selective deposition method can be attributed to the limited interaction of the Ti precursor used here with the PMMA copolymer active functional groups. Therefore, in addition to being advantageous due to less processing steps, the selective deposition method can be used for the fabrication of lower dimensional nanostructures by identifying proper precursors and polymers and by controlling the interaction parameters. Our results will be useful for exploring interactions of other polymers with inorganic material precursors and thereby fabricating different nanostructures with desired morphologies using a simple and cost-effective dipping method.