Molecular Beam Epitaxy Growth of Superconducting Sr1-xKxFe2As2 and Ba1-xKxFe2As2
We report on the molecular beam epitaxy growth of nonsuperconducting SrFe 2 As 2 and BaFe 2 As 2 and superconducting Sr 1-x K x Fe 2 As 2 and Ba 1-x K x Fe 2 As 2 thin films. SrFe 2 As 2 and BaFe 2 As 2 films were obtained rather easily at the growth temperatures of 540--600 °C, which are not much d...
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| Published in | Applied physics express Vol. 3; no. 9; pp. 093101 - 093101-3 |
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| Main Authors | , , , , , , |
| Format | Journal Article |
| Language | English |
| Published |
The Japan Society of Applied Physics
25.09.2010
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| Online Access | Get full text |
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| Summary: | We report on the molecular beam epitaxy growth of nonsuperconducting SrFe 2 As 2 and BaFe 2 As 2 and superconducting Sr 1-x K x Fe 2 As 2 and Ba 1-x K x Fe 2 As 2 thin films. SrFe 2 As 2 and BaFe 2 As 2 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 Sr 1-x K x Fe 2 As 2 and Ba 1-x K x Fe 2 As 2 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 (${\leq}350$ °C) in reduced As flux. The resultant films showed good superconducting properties: $T_{\text{c}}^{\text{on}}$ $(T_{\text{c}}^{\text{end}}) = 33.2$ K (30.0 K) and 38.3 K (35.5 K) for Sr 1-x K x Fe 2 As 2 and Ba 1-x K x Fe 2 As 2 thin films respectively. |
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| Bibliography: | (a) XRD patterns and (b) $\rho$--$T$ curves of Sr-122 films grown on r-cut Al 2 O 3 at different $T_{\text{s}}$. The As flux ($\aku p_{\text{As}}$) was kept ${\sim}5\times 10^{-5}$ Torr. The Sr-122 peaks appear in XRD at $T_{\text{s}}\geq 480$ °C. However, the $\rho$--$T$ curves show a kink at ${\sim}200$ K corresponding to the magnetic transition in the films grown at $T_{\text{s}} \geq 370$ °C. (a) XRD patterns and (b) $\rho$--$T$ curves of the (Sr,K)Fe 2 As 2 films grown on r-cut Al 2 O 3 at $T_{\text{s}} = 310$ °C with different As fluxes ($\aku p_{\text{As}}$) from $1\times 10^{-8}$ to $2\times 10^{-6}$ Torr. $\rho$--$T$ curves of the best (Sr,K)Fe 2 As 2 and (Ba,K)Fe 2 As 2 films on r-cut Al 2 O 3 so far obtained. The (Sr,K)Fe 2 As 2 film was grown at $T_{\text{s}} = 340$ °C with $p_{\text{As}} = 7\times 10^{-8}$ Torr whereas the (Ba,K)Fe 2 As 2 film was grown at $T_{\text{s}} = 340$ °C with $p_{\text{As}} = 3\times 10^{-8}$ Torr. |
| ISSN: | 1882-0778 1882-0786 |
| DOI: | 10.1143/APEX.3.093101 |