Preparation of mesoporous silica thin films at low temperature: a comparison of mild structure consolidation and template extraction procedures

Abstract

Mesoporous thin films (MTFs) displaying high surface area and controlled porosity constitute interesting materials for a plethora of applications in optics and electronics. A critical aspect in MTF processing is template removal that usually consists in thermal treatment at 350 °C, which consolidates the oxide film but might change the pore features. In addition, the use of such high temperature must be avoided when organic functionalities are to be preserved, or in the case of film deposition on polymeric substrates. Here we present and compare five different methods to consolidate silica MTF (SMTF) in mild conditions, at a maximum processing temperature of 130 °C. Conditions, such as duration of the thermal treatment, vacuum conditions, exposure to acidic and alkaline media, were systematically explored and the resulting films were analyzed by optical microscopy, focused ion beam, scanning electron microscopy, ellipsometry, and infrared spectroscopy. The optimized conditions leading to accessible mesopores and a stable oxide structure that can be used as a mesoporous perm-selective electrode are discussed.