Localized epitaxial growth of α-Al2O3 thin films on Cr2O3 template by sputter deposition at low substrate temperature

Low-temperature growth of α-Al2O3 films by sputtering was studied with x-ray diffraction and high-resolution transmission electron microscopy (HRTEM). Pure α-Al2O3 film was formed at 400 °C using Cr2O3 as template, whereas amorphous or θ-Al2O3 was formed without Cr2O3. HRTEM revealed localized epitaxial growth of α-Al2O3 on Cr2O3 with the relationship [011]Al2O3/[011]Cr2O3, suggesting the importance of Cr2O3 as a structural template for the growth of α-Al2O3, in addition to other contributions such as good stoichiometry, low sputter pressure, and low deposition rate under optimized deposition conditions. Successful growth of α-Al2O3 by sputtering at 400 °C or below makes the film widely applicable to even glass substrates.