Abstract: Rutile compounds have exotic functional properties that can be applied for various electronic applications; however, the limited availability of epitaxial substrates has restricted the study of rutile thin films to a limited range of lattice parameters. Here, rutile GeO₂ is demonstrated as a new rutile substrate with lattice parameters of 𝑎=4.398 Å and 𝑐=2.863 Å. Rutile GeO₂ single crystals up to 4 mm in size are grown by the flux method. X-ray diffraction reveals high crystallinity with a rocking curve having a full width half-maximum of 0.0572°. After mechanical polishing, a surface roughness of less than 0.1 nm was obtained, and reflection high-energy electron diffraction shows a crystalline surface. Finally, epitaxial growth of (110)-oriented TiO₂ thin films on GeO₂ substrates was demonstrated using molecular beam epitaxy. Templated by rutile GeO₂ substrates, our findings open the possibility of stabilizing new rutile thin films and strain states for the tuning of physical properties.

Full text available from Journal of Vacuum Science & Technology A