Plasma-assisted molecular beam epitaxy of SnO2 on TiO2

Epitaxial growth of SnO2 on TiO2 (1 1 0) substrates by plasma-assisted molecular beam epitaxy was studied under various growth conditions to explore the potential for high-quality single crystalline growth. Phase-pure (1 1 0)-oriented SnO2 films with an optimum on-axis X-ray rocking curve scan full-width at half-maximum equal to 0.612° were grown. The film epitaxy proceeded in the Volmer–Weber growth mode. We identified different growth regimes by measuring growth rate variations correlated with increasing tin fluxes at a fixed oxygen pressure. Beginning in the oxygen-rich growth regime, growth rates increased linearly as the tin flux increased. Atomically flat surfaces were observed in the oxygen-rich regime. Continued tin flux increases resulted in a maximum growth rate of 470 nm/h. Further tin flux increases prevented SnO2 formation on the growth surface and acted as a nucleation barrier of SnO2 on the TiO2 substrates identifying a metal-rich growth regime.