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Nanostructured Porous Quartz Films for Electronics
Clément Sanchez
p. 23

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Source: La lettre, no. 37, December 2013

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1Until now, it has been very difficult to purify and to nanostructure quartz, one of the crystalline phases of silica, and the second most abundant mineral in the world.

2Researchers from the Laboratoire de chimie de la matière condensée de Paris (CNRS/Collège de France/UPMC) have achieved an exceptional feat, in collaboration with the Barcelona Institute of Materials Science and the Institut Laue-Langevin in Grenoble: through a simple process, they have obtained a quartz film on a silicon substrate with crucial characteristics for micro-electronics. Why use quartz in this domain? For its piezoelectric properties, that is to say, the capacity to produce an electric charge under the effect of a mechanical constraint. This soft chemistry work is paving the way for huge reductions in the manufacturing cost of quartz films for electronics, and to their exploitation in new applications in that field. It was published in the journal Science on 17 May 2013.

3Quartz, a mineral species composed of silica (SiO2), is one of the most abundant minerals in the world. In electronics, it is valued for the piezoelectric properties of one of its conformations (α­quartz). This property, discovered in 1880 by the Curie brothers, enables it to be electrically polarized by a mechanical constraint and, conversely, to be deformed when subjected to an electric field. Piezoelectricity has a wide range of applications both in industry and in everyday life, from the ordinary gas lighter to piezoelectric resonators, pressure sensors and accelerometers, piezoelectric actuators and motors, microgenerators, piezoelectric transformers, filters in electronics, etc. Though it is abundant, natural quartz is neither sufficiently pure nor of a sufficiently high quality to be integrated into electronic devices. The quartz films currently used are increasingly obtained by slicing synthetic quartz produced at high temperatures and pressures.

4One of the areas of expertise of the hybrid materials and nanomaterials chemistry team (Chimie des matériaux hybrides et des nanomatériaux - MHN) headed by Clément Sanchez is hybridizing soft chemistry, which draws inspiration from living forms to synthesize original multiscale and multifunctional materials for use in the fields of energy, the environment, nanomedicine, and modern micro-optics and microelectronics. One of this team’s recent noteworthy achievements has been the development of new mesotextured quartz coatings, which represents a challenge that until recently seemed out of reach for the European, Japanese and US teams working on these themes.

5This research, which is operationally very simple even though it involves particularly complex reaction mechanisms, performed an entirely original feat under these temperature and pressure conditions: the use of amorphous silica to produce α­quartz (and not the crystalline phases of non-piezoelectric silica) crystallized symmetrically in relation to its silica substrate – epitaxial quartz to be more precise. This property, added to the porosity that can be controlled from the scale of the micron to that of several tens of nanometers, allows us to increase substantially the surface accessible to molecules, so as to develop ultra-accurate sensors for example. These piezoelectric materials developed through a delicate combination of soft chemistry with texturing agents and thermal treatment are cheaper, more easily integrated on microelectronics’ existing silica platforms, and offer more original textures than conventional quartz.

6The specificities of epitaxial meso- or macro-porous piezoelectric quartz open up a highly promising field of research and applications. The most obvious expectations concern both the development of intelligent sensors through sound wave modulation and modern microelectronics (developing processes for micro-electromechanics).

This work was published in the journal Science: A. Carretero-Genevrier, M. Gich, L. Picas, J. Gazquez, G.-L. Drisko, C. Boissiere, D. Grosso, J. Rodriguez-Carvajal, C. Sanchez, Science, 17 May 2013.

Prof. Clément Sanchez Chemistry of Hybrid Materials

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Clément Sanchez, « CHEMISTRY OF HYBRID MATERIALS », La lettre du Collège de France [En ligne], 8 | mars 2014, mis en ligne le 11 août 2015, consulté le 23 mars 2017. URL :

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Clément Sanchez

Chemistry of Hybrid Materials

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