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We report on the molecular beam epitaxy growth of nonsuperconducting SrFe2As2 and BaFe2As2 and superconducting Sr1-xKxFe2As2 and Ba1-xKxFe2As2 thin films. SrFe2As2 and BaFe2As2 films were obtained rather easily at the growth temperatures of 540–600 °C, which are not much different from those for GaAs growth. However, superconducting Sr1-xKxFe2As2 and Ba1-xKxFe2As2 films cannot be obtained at the same growth temperatures as elemental K is highly volatile. The key to incorporating K into films is low-temperature growth (≤350 °C) in reduced As flux. The resultant films showed good superconducting properties: Tcon (Tcend) = 33.2 K (30.0 K) and 38.3 K (35.5 K) for Sr1-xKxFe2As2 and Ba1-xKxFe2As2 thin films respectively.

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