Highly Ordered “Defect-Free” Self-Assembled Hybrid Films with a Tetragonal Mesostructure

Abstract

One-pot self-assembled hybrid films were synthesized by the cohydrolysis of methyltriethoxysilane and tetraethoxysilane and deposited via dip-coating. The films show a high "defect-free" mesophase organization that extends throughout the film thickness and for domains of a micrometer scale, as shown by scanning transmission electron microscopy. We have defined these films defect-free to describe the high degree of order that is achieved without defects in the pore organization, such as dislocations of pores or stacking faults. A novel mesophase, which is tetragonal I4/mmm (space group), is observed in the films. This phase evolves but retains the same symmetry throughout a wide range of temperatures of calcination. The thermal stability and the structural changes as a function of the calcination temperature have been studied by small-angle X-ray scattering, scanning transmission electron microscopy, and Fourier transform infrared spectroscopy. In situ Fourier transform infrared spectroscopy employing synchrotron radiation has been used to study the kinetics of film formation during the deposition. The experiments have shown that the slower kinetics of silica species can explain the high degree of organization of the mesostructure.

Single Step Preparation of Novel Hydrophobic Composite Films for Low‐k Applications

“…An ordered mesoporous silica film will be formed, if this solution is applied to a substrate by dip-or spin-coating. [13] However, it is much more complicated when this solution is mixed with OFS suspension to prepare composite films. OFS suspension is synthesized in strongly basic medium.…”

“…Such materials are synthesized typically by the traditional solgel process [3][4][5][6][7] or a template directed procedure. [8][9][10][11][12][13][14][15] Sol-gel derived silicas have a high porosity (60-90%) and offer a tunable k value, but their low mechanical stability, wide pore size distribution, and hydrophilicity limit their applications in microelectronic industry. Compared to sol-gel derived silica, surfactant-templated mesoporous silica has much more uniform and controllable pores.…”

Photonic Crystals from Ordered Mesoporous Thin‐Film Functional Building Blocks

“…The bifunctional molecules adsorb onto the titania and silica surface; however, molecules can be completely removed from the silica surface after thorough washing with THF [6]. Methyl functions are included in silica MPFs layers by a one-pot method, using MTES as a co-precursor [28]. Alternatively, one-pot methods that use organosilane precursors in combination with alkoxides or chlorides can be applied [29].…”

Order−Disorder in Self-Assembled Mesostructured Silica Films: A Concepts Review

“…Basically we can think about two different strategies to extend the scale order; one is trying to manage the film formation process by prepatterning the surface that allows a controlled epitaxial growth, while another one is based on the chemicalphysical process control during film formation. Two examples of these different strategies have been shown by Kuroda 54 et al who obtained highly ordered mesoporous films whose organization is extended for several centimeters and Falcaro et al 21,55 who have fabricated defect-free hybrid silica films even if in a shorter range.…”