We report MBE growth of the iron-based superconductors, Sr 1-xKxFe2As2, Ba 1-xKxFe2As2, and SmFeAs(O,F). In the growth of Sr1-xKxFe 2As2 and Ba1-xKxFe 2As2 films, the key to incorporating volatile K in films is low-temperature (300-350 °C) growth in reduced As flux. The highest Tc so far obtained are Tcon(Tcend)=33.4K (31.0 K) and 38.3 K (35.5 K) for Sr1-xKxFe2As2 and Ba1-xKxFe2As2, respectively. In the growth of superconducting SmFeAs(O,F), we have adopted two approaches. In the first approach, we first grew F-free SmFeAsO films, and subsequently introduced F to the films via F diffusion from an overlayer of SmF3 or NdF3. In the second approach, we attempted the growth of as-grown superconducting SmFeAs(O,F) films by coevaporating Sm, SmF3, Fe, and As. In both the approaches, the growth temperature was as high as 650 °C. So far better results have been obtained by the first F diffusion method. The films prepared by F diffusion showed Tcon (Tcend) = 52 K (48.6 K) whereas the as-grown films showed Tcon = 47 K but with a long transition tail.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering