The mid-T_(C) superconductor Ba1-XKXBiO3(BKBO)exhibits different superconducting mechanisms depending on x,in the range∼0.35–0.65.The optimal doping for the highest T_(C) is reported to be around x=0.4.To understand...The mid-T_(C) superconductor Ba1-XKXBiO3(BKBO)exhibits different superconducting mechanisms depending on x,in the range∼0.35–0.65.The optimal doping for the highest T_(C) is reported to be around x=0.4.To understand more about the dependence of the superconducting mechanism on x,high quality and reproducible epitaxial films with controlled x are needed.This has been challenging owing to the volatility of K and(to a lesser extent)Bi.In this work,we use pulsed laser deposition(PLD)with several novel process steps to achieve high-quality films in a reproducible way.These include a modified method for target preparation,a low NO_(2) growth pressure,and precise positioning of substrates in the PLD plume.Optimum T_(C) films(32 K onset)were grown from an x=0.4 target,i.e.with no excess K,as is normally used.Stable,higher K content films(made from an x=0.45 target),were also grown.These x=0.45 films had a lower T_(C) (22.5 K onset),as expected for(K)overdoped films,with very high upper critical field,H_(C2) (0 K),and irreversibility field,Hirr(0 K),values,from linear extrapolation,of∼31.7 T and∼28.8 T,respectively.The growth methodology demonstrated in this work is highly beneficial for fundamental mechanistic studies of this complex superconductor on which there is renewed interest,and where controlled compositions and crystalline quality are currently limited.展开更多
基金All the authors thank the ONRG-NICOP-N62909-18-1-2092 grant for funding this researchMuireann de h-Óra also thanks European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement number 861145–BeMAGIC for financial supportJudith L.MacManus-Driscoll also thanks the Royal Academy of Engineering Chair in Emerging Technologies grant-CIET1819\24 and the ERC grant EU-H2020-ERC-ADG#882929 EROS.
文摘The mid-T_(C) superconductor Ba1-XKXBiO3(BKBO)exhibits different superconducting mechanisms depending on x,in the range∼0.35–0.65.The optimal doping for the highest T_(C) is reported to be around x=0.4.To understand more about the dependence of the superconducting mechanism on x,high quality and reproducible epitaxial films with controlled x are needed.This has been challenging owing to the volatility of K and(to a lesser extent)Bi.In this work,we use pulsed laser deposition(PLD)with several novel process steps to achieve high-quality films in a reproducible way.These include a modified method for target preparation,a low NO_(2) growth pressure,and precise positioning of substrates in the PLD plume.Optimum T_(C) films(32 K onset)were grown from an x=0.4 target,i.e.with no excess K,as is normally used.Stable,higher K content films(made from an x=0.45 target),were also grown.These x=0.45 films had a lower T_(C) (22.5 K onset),as expected for(K)overdoped films,with very high upper critical field,H_(C2) (0 K),and irreversibility field,Hirr(0 K),values,from linear extrapolation,of∼31.7 T and∼28.8 T,respectively.The growth methodology demonstrated in this work is highly beneficial for fundamental mechanistic studies of this complex superconductor on which there is renewed interest,and where controlled compositions and crystalline quality are currently limited.
