Crystallization of GeO2 thin films into ?-quartz: from spherulites to single crystals

Piezoelectric quartz SiO2 crystals are widely used in industry as oscillators. As a natural mineral, and its relevant silicates also of interest geoscience mineralogy. However, the nucleation growth is difficult to control not fully understood. Here we report successful solid state crystallization thin film amorphous GeO2 into on various substrates including Al2O3, MgAl2O4, MgO, LaAlO3 SrTiO3. At relatively low annealing temperatures, process spherulitic: with fibers growing radially from centers crystal lattice rotating along direction linear dependence between rotation angle distance core. For increasingly higher begin form. The edges sample play an important role facilitating followed by sweeping inward until whole crystallized. Control allows single crystalline be synthesized. Our study reveals complexity provides insight for further studies.