Structure of Mesoporous Silica Thin Films Prepared by Contacting PEO106-PPO70-PEO106 Films with Vaporized TEOS
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- 作者：Shunsuke Tanaka ; Michael P. Tate ; Norikazu Nishiyama ; Korekazu Ueyama ; Hugh W. Hillhouse
- 刊名：Chemistry of Materials
- 出版年：2006
- 出版时间：November 14, 2006
- 年：2006
- 卷：18
- 期：23
- 页码：5461 - 5466
- 全文大小：343K
- 年卷期：v.18,no.23(November 14, 2006)
- ISSN：1520-5002
文摘
Highly ordered mesoporous silica thin films have been prepared on silicon substrates by contactingPEO106-PPO70-PEO106 (Pluronic F127) triblock copolymer films with hydrolyzed tetraethyl orthosilicate(TEOS) followed by calcination. 2D grazing angle of incidence small angle X-ray scattering (GISAXS)patterns analyzed in the context of the distorted wave Born-approximation (DWBA) show that the filmsare (111)-oriented and possess rhombohedral symmetry with lattice constants a = 16.8 nm and 
= 70
.Further, high resolution field emission scanning electron microscope (FESEM) observations showed thatthe films have a lamellar structure supported with periodically arranged pillars. To our knowledge thisis the first report of a rhombohedral mesophase obtained using Pluronic F127. Additionally, the poreconnectivity in the films here differs from previously reported rhombohedral films. Here the films arecapped with a dense layer of silica and appear to not have significant mesoporosity in the directionperpendicular to the substrate. As a result of this structure, after silylation the films have a low relativedielectric constant of ~1.86. In addition, by comparing the X-ray diffraction (XRD) patterns with theGISAXS analysis, we show how using Bragg's law to calculate d-spacings from XRD data can significantlyunderestimate the d-spacing. Taking into account the effects of refraction, we report a modified expressionof Bragg's law that may be used to recover accurate d-spacings from XRD data.
= 70.Further, high resolution field emission scanning electron microscope (FESEM) observations showed thatthe films have a lamellar structure supported with periodically arranged pillars. To our knowledge thisis the first report of a rhombohedral mesophase obtained using Pluronic F127. Additionally, the poreconnectivity in the films here differs from previously reported rhombohedral films. Here the films arecapped with a dense layer of silica and appear to not have significant mesoporosity in the directionperpendicular to the substrate. As a result of this structure, after silylation the films have a low relativedielectric constant of ~1.86. In addition, by comparing the X-ray diffraction (XRD) patterns with theGISAXS analysis, we show how using Bragg's law to calculate d-spacings from XRD data can significantlyunderestimate the d-spacing. Taking into account the effects of refraction, we report a modified expressionof Bragg's law that may be used to recover accurate d-spacings from XRD data.