Thin films of the [Formula: see text]-quartz [Formula: see text] solid solution

[Formula: see text] with the [Formula: see text]-quartz structure is one of the most popular piezoelectrics. It is widely used in crystal oscillators, bulk acoustic wave (BAW) devices, surface acoustic wave (SAW) devices, and so on. [Formula: see text] can also be crystallized into the [Formula: see text]-quartz structure and it has better piezoelectric properties, with higher piezoelectric coefficient and electromechanical coupling coefficients, than [Formula: see text]. Experiments on bulk crystals and theoretical studies have shown that these properties can be tuned by varying the Si/Ge ratio in the [Formula: see text] solid solution. However, to the best of our knowledge, thin films of [Formula: see text] quartz have never been reported. Here we present the successful crystallization of [Formula: see text] thin films in the [Formula: see text]-quartz phase on quartz substrates ([Formula: see text]) with x up to 0.75. Generally, the films grow semi-epitaxially, with the same orientation as the substrates. Interestingly, the [Formula: see text] composition grows fully strained by the quartz substrates and this leads to the formation of circular quartz domains with an ordered Dauphiné twin structure. These studies represent a first step towards the optimization of piezoelectric quartz thin films for high frequency (> 5 GHz) applications.

Preferred Orientation of Quartz in Metamorphic Rocks from the Bergell Alps

Crystal preferred orientation of 47 samples of quartzite and eight samples of associated marbles from the Bergell Alps have been analyzed with time-of-flight neutron diffraction and EBSD. The results show a clear distinction of texture types for quartzites transformed from Triassic sandstones and quartz layers in gneiss. Textures of Triassic quartzites are overall weak and display a maximum of c-axes perpendicular to the foliation or a crossed girdle perpendicular to the lineation. Pole figures for positive rhombs {10 1 ¯ 1} show a maximum perpendicular to the foliation and negative rhombs {01 1 ¯ 1} generally display a minimum. Based on polycrystal plasticity models this texture type can be attributed to a combination of basal and rhombohedral slip. Asymmetry of the distributions is attributed to simple shear and local strain heterogeneities. The relatively weak texture is partially caused by muscovite limiting dislocation motion and grain growth, as well as adjacent layers of marble that accommodate significant strain. Most quartz layers in gneiss, including mylonites, display a texture with a-axes parallel to the lineation and a c-axis maximum in the intermediate fabric direction. This texture type can be attributed to dominant prismatic slip. Many samples are recrystallized and recrystallization appears to strengthen the deformation texture. The study shows good agreement of neutron diffraction and EBSD. Neutron diffraction data average over larger volumes and maximum pole densities are generally lower and more representative for the bulk material. With EBSD the microstructure and mechanical twinning can be quantified.