Epitaxial growth of perovskite SrBiO 3 film on SrTiO 3 by oxide molecular beam epitaxy

Hole-doped perovskite bismuthates such as ${\mathrm{Ba}}_{1\ensuremath{-}x}{\mathrm{K}}_{x}{\mathrm{BiO}}_{3}$ and ${\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{K}}_{x}{\mathrm{BiO}}_{3}$ are well-known bismuth-based oxide high-transition-temperature superconductors. Reported thin bismuthate films show relatively low quality, likely due to their large lattice mismatch with the substrate and a low sticking coefficient of Bi at high temperatures. Here, we report the successful epitaxial thin film growth of the parent compound strontium bismuthate ${\mathrm{SrBiO}}_{3}$ on SrO-terminated ${\mathrm{SrTiO}}_{3}$ (001) substrates by molecular beam epitaxy. Two different growth methods, high-temperature codeposition or recrystallization cycles of low-temperature deposition plus high-temperature annealing, are developed to improve the epitaxial growth. ${\mathrm{SrBiO}}_{3}$ has a pseudocubic lattice constant $\ensuremath{\approx}4.25$ \AA{} and an $\ensuremath{\approx}8.8%$ lattice mismatch on ${\mathrm{SrTiO}}_{3}$ substrate, leading to a large strain in the first few unit cells. Films thicker than 6 unit cells prepared by both methods are fully relaxed to bulk lattice constant and have similar quality. Compared to high-temperature codeposition, the recrystallization method can produce higher quality 1- to 6-unit cell films that are coherently or partially strained. Photoemission experiments reveal the bonding and antibonding states close to the Fermi level due to Bi and O hybridization, in good agreement with density functional theory calculations. This work provides general guidance to the synthesis of high-quality perovskite bismuthate films.