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Accueil > Séminaires > Archives > Archives 2013

Silica particle and thin film structuration and transformation into ?-quartz

Glenna DRISKO, Laboratoire de Chimie de la Matière Condensée de Paris, Collége de France

par Leng Jacques - publié le

Architecture in silica thin films can be controlled from the nanometer to the micrometer scale using a variety of chemical methods, including self-assembly and phase separation. Physical methods, such as reactive ion etching may also be used to pattern thin films when combined with a selective mask. In this seminar, I will discuss the most recent advances from our laboratory in the architectural design of silica thin films, along with their resulting properties.
Historically, the LCMCP has used the principles of evaporation induced self-assembly of well-defined nano-objects combined with dip-coating in a set environment to control film thickness, mesopore size, organization and chemical composition. We have now extended our work into macroporous thin films constructed via a salt and surfactant mediated nucleation and growth methodology. Perforation diameters between 75 and 2000 nm can be controllably deposited by adapting deposition conditions. These films were converted to epitaxial ?-quartz thanks to the inclusion of the salts in the silica matrix, which acted as melting agents. Epitaxy, and therefore piezoelectricity, was generated due to the mismatch with the crystalline silicon substrate.
The crystallization behavior was then studied in block copolymer templated thin films and particles. A post-synthetic infiltration of alkaline earths was performed to study the effects of concentration and cation nature. The morphology of the films was characterized using ellipsometry, GI-SAXS, SEM and TEM. A minimum pore size of 40 nm was conserved in the crystalline silica matrix. Core-shell particles with a core diameter of 80 nm preserved their architecture, however without intimate contact with a crystalline substrate, the colloids were polymorphic and polycrystalline.
Quartz has many advantages over its amorphous counterpart, including UV transparency, lower solubility in aqueous solutions, increased hardness and piezoelectricity. Thus crystalline silica is used in optics, biomedicine, abrasion and electronics. Structured epitaxial quartz films such as those reported here, may find application in BioMEMs and microfluidics.