Structural comparison of hexagonally ordered mesoporous thin films developed by dip- and spin-coating using X-ray reflectometry and other quantitative X-ray techniques

Abstract

Clear and homogeneous precursors for casting mesoporous thin films (MTFs) were prepared by addition of a triblock polyalkylene oxide amphiphilic surfactant (the structural directing agent) to a clear sol of tetraethylorthosilicate. Films were developed by dip- and spin-coating methods and calcined to yield high quality crack-free coatings containing highly ordered hexagonal arrangements of mesopores. Comparison of the dip-coating and spin-coating methods was made using X-ray methods including powder X-ray diffraction, reciprocal space mapping, X-ray reflectometry and in-plane scattering. In all cases, the films had a highly textured nature with preferential alignment of pores parallel to the substrate. It was found that the dip-coating method resulted in better quality films with greater long range order. The varied X-ray methods provided a detailed structural analysis of the mesoporous thin films which showed a distorted hexagonal arrangement. The results defining pore size could be directly and favourably compared to TEM and N₂ isotherm data. It was found that all the techniques are in reasonable agreement.