Nano/micro-patterning of anatase TiO₂thin film from an aqueous solution by site-selective elimination method

Abstract

We proposed a novel method to fabricate nano/micro-scaled patterns of thin films and successfully fabricated patterns of anatase TiO 2 thin films in an aqueous solution at 50 8C. The patterned self-assembled monolayer (SAM) having octadecyltrichlorosilane (OTS) regions and silanol regions was immersed in a solution containing a Ti precursor and subjected to ultrasonication for several hours. The difference in adhesion of thin films on substrates was employed for the site-selective elimination method. Heterogeneously nucleated TiO 2 and homogeneously nucleated TiO 2 particles adhering to the OTS -SAM could be easily eliminated from the substrate by ultrasonication, whereas those on silanol groups maintained their adhesion during the immersion period. TiO 2 can form chemical bonds such as Ti -O-Si with silanol groups, but cannot form them with octadecyl groups, resulting in the difference in adhesion, which is the essence of the siteselectivity of this method. The site-selective elimination method can be applied to fabricate nano/micro-scaled patterns in the solution by the immersion of the substrate that has regions on which depositions adhere strongly and regions on which depositions adhere weakly, enabling elimination by treatment such as ultrasonication. q

Morphology Control of Metal Oxide Nanocrystals

“…The particles were homogeneously nucleated in the solution, turning the solution white. Deposition of anatase TiO 2 proceeds by the following mechanisms 43 (Fig. 16).…”

Nanofabrication of Metal Oxide Patterns Using Self-Assembled Monolayers

“…Liquid phase patterning of crystalline aanatase TiO 2 thin films using site-selective elimination 40 Ammonium hexafluorotitanate ([NH 4 ] 2 TiF 6 ) (purity 96%, 1.031 g) and boric acid (H 3 BO 3 ) (purity 99.5%, 0.932 g) were dissolved separately in deionized water (50°C, 50 ml) 40 . An appropriate amount of HCl was added to the boric acid solution to control pH, and ammonium hexafluorotitanate solution was added.…”

“…40 For the adhesion of TiO 2 films to silanol groups, the pH of the deposition solution is critical. Pizem et al 13 reported that adherent TiO 2 films formed from solutions similar to those used here at pH=3.9, but that the films were less adherent at pH=2.9.…”

Nano/Micro-Patterning of Metal Oxide Nanocrystals

“…Liquid phase patterning of crystalline anatase TiO 2 thin films using site-selective elimination 40 Ammonium hexafluorotitanate ([NH 4 ] 2 TiF 6 ) (purity 96%, 1.031 g) and boric acid (H 3 BO 3 ) (purity 99.5%, 0.932 g) were dissolved separately in deionized water (50°C, 50 ml) 40 . An appropriate amount of HCl was added to the boric acid solution to control pH, and ammonium hexafluorotitanate solution was added.…”