In this study, we have explored the ways to fabricate and optimize high-quality ultrathin YBa2 Cu3 O7-δ(YBCO) films grown on single-crystal(001) SrTiO3 substrates. Nearly atomic-flat YBCO films are obtained by pulsed...In this study, we have explored the ways to fabricate and optimize high-quality ultrathin YBa2 Cu3 O7-δ(YBCO) films grown on single-crystal(001) SrTiO3 substrates. Nearly atomic-flat YBCO films are obtained by pulsed laser deposition.Our result shows that the termination of SrTiO3 has only a negligible effect on the properties of YBCO. In contrast, we found that capping a non-superconducting oxide layer can generally enhance the superconductivity of YBCO. PrBa2 Cu3 O7,La2 CuO4, LaMnO3, SrTiO3, and LaAlO3 have been examined as capping layers, and the minimum thickness of superconducting YBCO with capping is ~ 2 unit cells–3 unit cells. This result might be useful in constructing good-performance YBCO-based field effect devices.展开更多
We describe the fabrication of high performance YBa2Cu3O7-δ （YBCO） radio frequency （RF） superconducting quantum interference devices （SQUIDs）, which were prepared on 5 mm×5 mm LaAlO3 （LAO） substrates by ...We describe the fabrication of high performance YBa2Cu3O7-δ （YBCO） radio frequency （RF） superconducting quantum interference devices （SQUIDs）, which were prepared on 5 mm×5 mm LaAlO3 （LAO） substrates by employing stepedge junctions （SEJs） and in flip-chip configuration with 12 mm×12 mm resonators. The step in the substrate was produced by Ar ion etching with step angles ranging from 47° to 61°, which is steep enough to ensure the formation of grain boundaries （GBs） at the step edges. The YBCO film was deposited using the pulsed laser deposition （PLD） technique with a film thickness half of the height of the substrate step. The inductance of the SQUID washer was designed to be about 157 pH. Under these circumstances, high performance YBCO RF SQUIDs were successfully fabricated with a typical flux-voltage transfer ratio of 83 mV/φ0, a white flux noise of 29 μφ0/√Hz, and the magnetic field sensitivity as high as 80 fT/√Hz. These devices have been applied in magnetocardiography and geological surveys.展开更多
YBa2Cu3O7-x（YBCO） films with co-doping BaTiO3（BTO） and Y2O3 nanostructures were prepared by metal organic deposition using trifluoroacetates（TFA-MOD）. The properties of the BTO/Y2O3co-doped YBCO films with diffe...YBa2Cu3O7-x（YBCO） films with co-doping BaTiO3（BTO） and Y2O3 nanostructures were prepared by metal organic deposition using trifluoroacetates（TFA-MOD）. The properties of the BTO/Y2O3co-doped YBCO films with different excess yttrium have been systematically studied by x-ray diffraction（XRD）, Raman spectra, and scanning electron microscope（SEM）. The optimized content of yttrium excess in the BTO/Y2O3co-doped YBCO films is 10 mol.%, and the critical current density is as high as - 17 mA/cm^2（self-field, 65 K） by the magnetic signal. In addition, the Y2Cu2O5 was formed when the content of yttrium excess increases to 24 mol.%, which may result in the deterioration of the superconducting properties and the microstructure. The unique combination of the different types of nanostructures of BTO and Y2O3 in the doped YBCO films, compared with the pure YBCO films and BTO doped YBCO films, enhances the critical current density（JC） not only at the self-magnetic field, but also in the applied magnetic field.展开更多
采用直流溅射法在Y2O3/Y S Z/C e O2(Y Y C)缓冲层的织构N i W基带上,通过基片温度调制YBa2Cu3O7-δ(YBCO)外延薄膜生长。X射线衍射仪(XRD)表征显示,基片温度强烈地影响YBCO薄膜的外延生长:在较低的基片温度下薄膜趋于a轴取向生长,随基...采用直流溅射法在Y2O3/Y S Z/C e O2(Y Y C)缓冲层的织构N i W基带上,通过基片温度调制YBa2Cu3O7-δ(YBCO)外延薄膜生长。X射线衍射仪(XRD)表征显示,基片温度强烈地影响YBCO薄膜的外延生长:在较低的基片温度下薄膜趋于a轴取向生长,随基片温度升高薄膜逐渐变为纯c轴取向生长。由于a轴晶粒引起的大角度晶界会阻碍超导电流在a-b面内的传输,因此YBCO薄膜的微观结构和超导电性能随温度升高而得到改善,但是随着基片温度继续升高,基带的氧化程度加剧,YBCO与缓冲层间发生界面反应,从而导致薄膜质量衰退。本研究还计算了YBCO薄膜中的位错密度,并研究了位错密度与自场下YBCO薄膜临界电流密度(Jc)之间的关系。结果表明:YBCO薄膜在自场下的临界电流密度对螺旋位错密度比对刃型位错密度更加敏感,这主要是由YBCO薄膜的螺旋生长机制引起的。展开更多
基金国家自然科学基金(批准号:11004129,11204171)留学回国人员科研启动基金(SRF for ROCS,SEM)+2 种基金上海市教育委员会科研创新项目(批准号:11YZ197,12ZZ174)上海市教育发展基金会晨光计划(批准号:12CG63)上海高校选拔培养优秀青年教师科研专项基金(批准号:sdl10005)资助的课题~~
基金Project supported by the National Key Research and Development Program of the Ministry of Science and Technology of China(Grants Nos.2017YFA0303002and 2016YFA0300204)the Fundamental Research Funds for the Central Universities,China
文摘In this study, we have explored the ways to fabricate and optimize high-quality ultrathin YBa2 Cu3 O7-δ(YBCO) films grown on single-crystal(001) SrTiO3 substrates. Nearly atomic-flat YBCO films are obtained by pulsed laser deposition.Our result shows that the termination of SrTiO3 has only a negligible effect on the properties of YBCO. In contrast, we found that capping a non-superconducting oxide layer can generally enhance the superconductivity of YBCO. PrBa2 Cu3 O7,La2 CuO4, LaMnO3, SrTiO3, and LaAlO3 have been examined as capping layers, and the minimum thickness of superconducting YBCO with capping is ~ 2 unit cells–3 unit cells. This result might be useful in constructing good-performance YBCO-based field effect devices.
基金supported by the National Basic Research Program of China(Grant No.2011CBA00106)the National Natural Science Foundation of China(Grant No.11074008)the Research Fund for the Doctoral Program of Higher Education,China(Grant No.20100001120006)
文摘We describe the fabrication of high performance YBa2Cu3O7-δ （YBCO） radio frequency （RF） superconducting quantum interference devices （SQUIDs）, which were prepared on 5 mm×5 mm LaAlO3 （LAO） substrates by employing stepedge junctions （SEJs） and in flip-chip configuration with 12 mm×12 mm resonators. The step in the substrate was produced by Ar ion etching with step angles ranging from 47° to 61°, which is steep enough to ensure the formation of grain boundaries （GBs） at the step edges. The YBCO film was deposited using the pulsed laser deposition （PLD） technique with a film thickness half of the height of the substrate step. The inductance of the SQUID washer was designed to be about 157 pH. Under these circumstances, high performance YBCO RF SQUIDs were successfully fabricated with a typical flux-voltage transfer ratio of 83 mV/φ0, a white flux noise of 29 μφ0/√Hz, and the magnetic field sensitivity as high as 80 fT/√Hz. These devices have been applied in magnetocardiography and geological surveys.
基金Project supported by the National Natural Science Foundation of China(Grant No.51272250)the National Basic Research Program of China(Grant No.2011CBA00105)+1 种基金the National High Technology Research and Development Program of China(Grant No.2014AA032702)the Natural Science Foundation of Beijing,China(Grant No.2152035)
文摘YBa2Cu3O7-x（YBCO） films with co-doping BaTiO3（BTO） and Y2O3 nanostructures were prepared by metal organic deposition using trifluoroacetates（TFA-MOD）. The properties of the BTO/Y2O3co-doped YBCO films with different excess yttrium have been systematically studied by x-ray diffraction（XRD）, Raman spectra, and scanning electron microscope（SEM）. The optimized content of yttrium excess in the BTO/Y2O3co-doped YBCO films is 10 mol.%, and the critical current density is as high as - 17 mA/cm^2（self-field, 65 K） by the magnetic signal. In addition, the Y2Cu2O5 was formed when the content of yttrium excess increases to 24 mol.%, which may result in the deterioration of the superconducting properties and the microstructure. The unique combination of the different types of nanostructures of BTO and Y2O3 in the doped YBCO films, compared with the pure YBCO films and BTO doped YBCO films, enhances the critical current density（JC） not only at the self-magnetic field, but also in the applied magnetic field.
文摘采用直流溅射法在Y2O3/Y S Z/C e O2(Y Y C)缓冲层的织构N i W基带上,通过基片温度调制YBa2Cu3O7-δ(YBCO)外延薄膜生长。X射线衍射仪(XRD)表征显示,基片温度强烈地影响YBCO薄膜的外延生长:在较低的基片温度下薄膜趋于a轴取向生长,随基片温度升高薄膜逐渐变为纯c轴取向生长。由于a轴晶粒引起的大角度晶界会阻碍超导电流在a-b面内的传输,因此YBCO薄膜的微观结构和超导电性能随温度升高而得到改善,但是随着基片温度继续升高,基带的氧化程度加剧,YBCO与缓冲层间发生界面反应,从而导致薄膜质量衰退。本研究还计算了YBCO薄膜中的位错密度,并研究了位错密度与自场下YBCO薄膜临界电流密度(Jc)之间的关系。结果表明:YBCO薄膜在自场下的临界电流密度对螺旋位错密度比对刃型位错密度更加敏感,这主要是由YBCO薄膜的螺旋生长机制引起的。
