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

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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.