Soft-chemistry-based routes to epitaxial α-quartz thin films with tunable textures.

Carretero-Genevrier, A; Gich, M; Picas, L; Gazquez, J; Drisko, G L; Boissiere, C; Grosso, D; Rodriguez-Carvajal, J et al. · Science · 2013

basic_science · Level V

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Abstract

Piezoelectric nanostructured quartz films of high resonance frequencies are needed for microelectronic devices; however, synthesis methods have been frustrated by the inhomogeneous crystal growth, crystal twinning, and loss of nanofeatures upon crystallization. We report the epitaxial growth of nanostructured polycrystalline quartz films on silicon [Si(100)] substrates via the solution deposition and gelation of amorphous silica thin films, followed by thermal treatment. Key to the process is the combined use of either a strontium (Sr(2+)) or barium (Ba(2+)) catalyst with an amphiphilic molecular template. The silica nanostructure constructed by cooperative self-assembly permits homogeneous distribution of the cations, which are responsible for the crystallization of quartz. The low mismatch between the silicon and α-quartz cell parameters selects this particular polymorph, inducing epitaxial growth.