Epitaxial Growth, Morphology, and Temperature Stability of Quartz-Like Germanium Dioxide Crystals

The conditions and mechanisms of epitaxial growth of quartz-like α-GeO2 crystals on quartz substrates using an evaporative-recirculation method are considered. Relatively homogenous α-GeO2 crystals weighing up to 200 g are grown at a growth rate of up to 0.3 mm/day. It is established that molecular adhesion (cohesion) at the boundary between the quartz substrate and the overgrown layer of α-GeO2 cannot prevent its transition to a stable poorly soluble rutile-like phase. This makes it impossible to grow high-germanium quartz single crystals industrially using a mixture of quartz and quartz-like α-GeO2 as a batch. However, this process can be implemented if other more soluble germanium-containing compounds, such as quartz-like Si-containing germanium-oxide, are found.