For obtaining pure phase T12Ba2Ca2Cu3O10 (T1-2223) films with good superconducting properties, the growth technique is improved by dc magnetron sputtering and a triple post-annealing process. The triple post-anneali...For obtaining pure phase T12Ba2Ca2Cu3O10 (T1-2223) films with good superconducting properties, the growth technique is improved by dc magnetron sputtering and a triple post-annealing process. The triple post-annealing process comprises annealing twice in argon and once in oxygen at different temperatures. In the first low-temperature annealing phase in argon, T12Ba2CaCu2O8 (T1-2212) is obtained to effectively minimize evaporation in the next step. With the increase of temperature in the second annealing stage in argon, the previously prepared T1-2212 inter-phase is converted into T1-2223 phase. An additional annealing in oxygen is also adopted to improve the properties of T1-2223 films, each containing an optimal oxygen content value. The results of X-ray diffraction (XRD) θ-2θ scans, 09 scans and rotational φ scans show that each of the T1-2223 films has a high phase purity and an epitaxial structure. Smooth films are observed by scanning electron microscopy (SEM). The critical temperatures Tc of the films are measured to be about 120 K and the critical current densities Jc can reach 4.0 MA/cm2 at 77 K at self field.展开更多
A new improved two-step method in fabricating Tl2Ba2 CaCu2O8(Tl-2212) thin films is presented in this paper. In the first process of dc magnetron sputtering, the thallium content in the precursor film is largely inc...A new improved two-step method in fabricating Tl2Ba2 CaCu2O8(Tl-2212) thin films is presented in this paper. In the first process of dc magnetron sputtering, the thallium content in the precursor film is largely increased by adjusting the ratio of thallium in the sputtering targets. After the second annealing process in the absence of additional thallium pellets or powder source, high-quality Tl-2212 thin films can be obtained. The proper content of thallium in the precursor film provides a relatively stable atmosphere to guarantee the growth of Tl-2212 film. This method avoids the repeated production of the thallium pellets in the post-annealing process, the repeatability and controllability of the experiment are greatly improved. X-ray diffraction(XRD) scans show that all of the sharp peaks of the sample films can be assigned to the(00 l) peaks of Tl-2212 phase. The highest superconducting critical temperature(Tc) of the films is 105 K and the critical current density(Jc) can achieve 1.93 MA/cm2 in zero magnetic field at 77 K for a 600 nm film.展开更多
Values of critieal eurrent densityJ。exceeding lo6A·em一2 at 77K and zerofield have been rePorted for thinmagnetlcfllnls ofYBaoCu:O,on sinZle ervstal substrates ofSrTIO:〔l一3)and一MgO(4,5)by manvfeseafCnerS.bllt...Values of critieal eurrent densityJ。exceeding lo6A·em一2 at 77K and zerofield have been rePorted for thinmagnetlcfllnls ofYBaoCu:O,on sinZle ervstal substrates ofSrTIO:〔l一3)and一MgO(4,5)by manvfeseafCnerS.bllt tne rCSUltS OIJ、)IU一A’cm一IorY廿tU Illms on suoslrale 01 slngleerystal ZrO:(100)have not been found out inPublished PaPers 50 far.Owing to themierostrueture eharacters and highJ。ofYBCO films by contrast with bulk it 15 themost Possible to aPPly the fllms to eleetronicfield first.Therefore it 15 more signifieant toimProve values ofjcsubstrate with betterPIOCeSSJc>展开更多
The rocking curve of Tl-2212 thin films in Fig.2 of our original paper[1]should be replaced with the following new one.Accordingly,in the fifth paragraph of Section 3 of the original paper,the statement“The full widt...The rocking curve of Tl-2212 thin films in Fig.2 of our original paper[1]should be replaced with the following new one.Accordingly,in the fifth paragraph of Section 3 of the original paper,the statement“The full width at half maximum(FWHM)of the(0012)peak of the Tl-2212 phase is about 0.24°”should be“The full width at half maximum(FWHM)of the(0012)peak of the Tl-2212 phase is about 0.42°”.展开更多
Superconducting transition edge sensor(TES)bolometers require superconducting films to have controllable transition temperatures T_(c)in different practical applications.The value of T_(c)strongly affects thermal cond...Superconducting transition edge sensor(TES)bolometers require superconducting films to have controllable transition temperatures T_(c)in different practical applications.The value of T_(c)strongly affects thermal conductivity and thermal noise performance of TES detectors.Al films doped with Mn(Al-Mn)of different concentrations can accomplish tunable T_(c)A magnetron sputtering machine is used to deposit the Al-Mn films in this study.Fabrication parameters including sputtering pressure and annealing process are studied and their influences on T_(c)and superconducting transition widthΔT_(c)are optimized.The Al-Mn films withΔT_(c)below 1.0 mK for T_(c)in a range of 520 mK-580 mK are successfully fabricated.展开更多
Disordered superconducting materials like NbTiN possess a high kinetic inductance fraction and an adjustable critical temperature, making them a good choice for low-temperature detectors. Their energy gap(D), critical...Disordered superconducting materials like NbTiN possess a high kinetic inductance fraction and an adjustable critical temperature, making them a good choice for low-temperature detectors. Their energy gap(D), critical temperature(T_(c)),and quasiparticle density of states(QDOS) distribution, however, deviate from the classical BCS theory due to the disorder effects. The Usadel equation, which takes account of elastic scattering, non-elastic scattering, and electro–phonon coupling,can be applied to explain and describe these deviations. This paper presents numerical simulations of the disorder effects based on the Usadel equation to investigate their effects on the △, Tc, QDOS distribution, and complex conductivity of the NbTiN film. Furthermore, NbTiN superconducting resonators with coplanar waveguide(CPW) structures are fabricated and characterized at different temperatures to validate our numerical simulations. The pair-breaking parameter α and the critical temperature in the pure state T_(c)^(P) of our NbTiN film are determined from the experimental results and numerical simulations. This study has significant implications for the development of low-temperature detectors made of disordered superconducting materials.展开更多
High quality Nb films were successfully prepared on both flexible polyimide(PI)and rigid Al2O3substrates and their transport properties were systematically studied at various applied currents,external magnetic fields,...High quality Nb films were successfully prepared on both flexible polyimide(PI)and rigid Al2O3substrates and their transport properties were systematically studied at various applied currents,external magnetic fields,and sample orientations.It is found that a curved Nb/PI film exhibits quite different superconducting transition and vortex dynamics compared to the flat Nb/Al2O3film.For the curved Nb/PI film,smooth superconducting transitions were obtained at low currents,while unexpected cascade structures were revealed in theρ(T)curves at high currents.We attribute this phenomenon to the gradient distribution of vortex density together with a variation of superconductivity along the curved film.In addition,reentrant superconductivity was induced in the curved Nb/PI thin film by properly choosing the measurement conditions.We attribute this effect to the vortex pinning from both in-plane vortices and out-of-plane vortices.This work reveals the complex transport properties of curved superconducting thin films,providing important insights for further theoretical investigations and practical developments of flexible superconductors.展开更多
We find that the superconductivity in the thin films of the formerly believed non-superconducting parent compound FeTe is accompanied by an emergence of second order with a correlation length of 742 nm and 258 nm at 1...We find that the superconductivity in the thin films of the formerly believed non-superconducting parent compound FeTe is accompanied by an emergence of second order with a correlation length of 742 nm and 258 nm at 10 K and 300 K, respectively. The structural phase transition found in iron pnictide superconductors, in non-superconducting FeTe bulk samples, and in FeSe superconducting thin films is not observed in the superconducting FeTe thin films. The interplay between superconductivity and long range order may suggest the crucial role of competition between electronic localization and itinerancy which leads to strong quantum fluctuations in the FeTe system.展开更多
The patterning technologies and process order of high Tc(86K) super-conducting film bolometers have been studied. After the deposition, a conventional lithographic process was used to pattern the films with aqueous so...The patterning technologies and process order of high Tc(86K) super-conducting film bolometers have been studied. After the deposition, a conventional lithographic process was used to pattern the films with aqueous solution of HCl, and then the films were transferred into a tube furnace for annealing to form superconducting film. It eliminates the degradation of patterning process. The bolometric responsivity of approximately 34. 32 V/W is measured, and the detectivity is greater than 1. 62× 108cm · Hz1/2 · W-1, the noise equivalent powers NEP is 2. 1×10-9W.展开更多
Laser ablated high temperature superconducting and related thin films are investigated with a microscopical point of view.The microstructure and microchemistry of three thin films(Y-Ba-Cu-O, Bi-Pb-Sr-Ca-Cu-O and Sr-Ca...Laser ablated high temperature superconducting and related thin films are investigated with a microscopical point of view.The microstructure and microchemistry of three thin films(Y-Ba-Cu-O, Bi-Pb-Sr-Ca-Cu-O and Sr-Ca-Cu-O)are demonstrated as examples of laser ablation products.展开更多
Systemic measurements show that there is no 3D to 2D crossover in the reduction of the superconducting transition temperature Tc in Nb thin films. This result is consistent with all previous measurements while it is c...Systemic measurements show that there is no 3D to 2D crossover in the reduction of the superconducting transition temperature Tc in Nb thin films. This result is consistent with all previous measurements while it is contrary to the prevailing understanding based on the interplay between proximity, localization, and lifetime broadening. Our study indicates that the decrease of Tc can be interpreted by the combined effects of electron-phonon coupling parameter λ and the defect scattering rate pw, being uniquely determined by their ratio λ/ρw. Other factors such as film thickness and irradiation do not produce additional effects beyond these two parameters.展开更多
Multicomponent superconductors exhibit nontrivial vortex behaviors due to the various vortex–vortex interactions,including the competing one in the recently proposed type-1.5 superconductor.However,potential candidat...Multicomponent superconductors exhibit nontrivial vortex behaviors due to the various vortex–vortex interactions,including the competing one in the recently proposed type-1.5 superconductor.However,potential candidate that can be used to study the multicomponent superconductivity is rare.Here,we prepared an artificial superconducting multilayer to act as an alternative approach to study multicomponent superconductivity.The additional repulsive length and the coupling strength among superconducting films were regulated by changing the thickness of the insulting layer.The magnetization measurements were performed to clarify the effect of the competition between the repulsive vortex interactions on the macroscopic superconductivity.The vortex phase diagram and the optimum critical current density have been determined.Furthermore,a second magnetization effect is observed,and is attributed to the upper layer,which provides the weak pinning sites to localize the flux lines.The pinning behaviors switches to the mixed type with the increase of the insulting layer thicknesses.Our results open a new perspective to the study and related applications of the multilayer superconducting systems.展开更多
YBa2Cu3O7(YBCO) thin films have been prepared by thermal coevaporation on LaAlO3(LAO) substrates, and Tl2Ba2CaCu2O8(TBCCO) thin films are synthesized by magnetron sputtering method on LAO substrates. The transit...YBa2Cu3O7(YBCO) thin films have been prepared by thermal coevaporation on LaAlO3(LAO) substrates, and Tl2Ba2CaCu2O8(TBCCO) thin films are synthesized by magnetron sputtering method on LAO substrates. The transition temperature Tc is 90 K forYBCO/LAO and 104 K for TBCCO/LAO. Microwave responses of the films are studied systematically by coplanar resonator technique. Energy gaps of the films obtained are △0 = 1.04kBTc for YBCO films and △0 =0.84kBTc for TBCCO films by analysing the temperature dependence of resonant frequencies of coplanar resonator. Penetration depth at 0 K A0 = 198.nm for YBCO films and A0 = 200 nm for TBCCO films could also be obtained by using the weak coupling theory and two fluid theory. Results of penetration depth and energy gap confirm the weak coupling properties of the films. In addition, microwave surface resistances Rs of YBCO/LAO and TBCCO/LAO are also investigated by analysing the quality factor and insert loss of the coplanar resonator. Surface resistance of TBCCO/LAO is less than that of YBCO/LAO, so that TBCCO/LAO films may have more potential applications.展开更多
Our recent progress in the fabrication of FeSe and KxFe2_ySe2 ultra thin films and the understanding of their superconductivity properties is reviewed. The growth of high-quality FeSe and KxFe2_ySe2 films is achieved ...Our recent progress in the fabrication of FeSe and KxFe2_ySe2 ultra thin films and the understanding of their superconductivity properties is reviewed. The growth of high-quality FeSe and KxFe2_ySe2 films is achieved in a well controlled manner by molecular beam epitaxy. The high-quality stoichiometric and superconducting crystalline thin films allow us to investigate the intrinsic superconductivity properties and the interplay between the superconductivity and the film thickness, the local structure, the substrate, and magnetism. In situ low-temperature scanning tunneling spectra reveal the nodes and the twofold symmetry in FeSe, high-temperature superconductivity at the FeSe/SrTiO3 interface, phase separation and magnetic order in KxFe2_ySe2, and the suppression of superconductivity by twin boundaries and Fe vacancies. Our findings not only provide fundamental information for understanding the mechanism of unconventional superconductivity, but also demonstrate a powerful way of engineering superconductors and raising the transition temperature.展开更多
High quality epitaxial YBa2Cu3O7-δ (YBCO) superconducting films were fabricated on (00l) LaAlO3 substrates using the direct-current sputtering method. The attainment of an unusually high film thickness (up to 2...High quality epitaxial YBa2Cu3O7-δ (YBCO) superconducting films were fabricated on (00l) LaAlO3 substrates using the direct-current sputtering method. The attainment of an unusually high film thickness (up to 2.0 μm) without mi-crocracking was attributed in part to the presence of pores correlated with yttrium-rich composition in the films. The influ-ence of the film thickness on the microstructure was investigated by X-ray diffraction conventional scan (θ-2θ,ω-scan,pole figure) and high-resolution reciprocal space mapping. The films were c-axis oriented with no a-axis-oriented grains up to the thickness of 2 μm. The surface morphology and the critical current density (Jc) strongly depended on the film thickness. Furthermore,the reasons for these thickness dependences were elucidated in detail.展开更多
Large area YBCO superconductive films prepared by d.c. magnetron sputtering have reached: T c>89 K, J c>3.5×10 6 A/cm 2 (77 K, 0 T), R s=0.25 mΩ, at 77.5 K, 9894 MHz. The microstructure an...Large area YBCO superconductive films prepared by d.c. magnetron sputtering have reached: T c>89 K, J c>3.5×10 6 A/cm 2 (77 K, 0 T), R s=0.25 mΩ, at 77.5 K, 9894 MHz. The microstructure analysis of the film showed it has fine monocrystalline structure and the crystalline perfectness is satisfactory. The oscillator, filter and antenna made from these films are good in performance. Therefore, YBCO superconductive films have great prospect in application.展开更多
The discovery of an extraordinarily superconductive large energy gap in SrTiO3 supported single-layer FeSe films has recently initiated a great deal of research interests in surface-enhanced superconductivity and supe...The discovery of an extraordinarily superconductive large energy gap in SrTiO3 supported single-layer FeSe films has recently initiated a great deal of research interests in surface-enhanced superconductivity and superconductive ultrathin films fabricated on crystal surfaces. On account of the instability of ultra-thin films in air, it is desirable to perform elec- trical transport measurement in ultra-high vaccum (UHV). Here we review the experimental techniques of in situ electrical transport measurement and their applications on superconductive ultrathin films.展开更多
A square hole array is fabricated over a micro-bridge of NbN thin film by electron beam lithography and reactive ion milling. Magneto-resistance is measured across the micro-bridge filled with a hole array near the su...A square hole array is fabricated over a micro-bridge of NbN thin film by electron beam lithography and reactive ion milling. Magneto-resistance is measured across the micro-bridge filled with a hole array near the superconducting transition temperature. It is found that magneto-resistance minima occur when the number of vortices is an integer multiple or a fractional multiple of the number of holes. The temperature and the current dependences of the matching effect are studied.展开更多
In this paper, we discuss the vortex structure of the superconducting thin films placed in a magnetic field. We show that the global minimizer of the functional modelling the superconducting thin films has a bounded n...In this paper, we discuss the vortex structure of the superconducting thin films placed in a magnetic field. We show that the global minimizer of the functional modelling the superconducting thin films has a bounded number of vortices when the applied magnetic field hex 〈 Hc1 + K log | logε| where Hc1 is the lower critical field of the film obtained by Ding and Du in SIAM J. Math. Anal., 2002. The locations of the vortices are also given.展开更多
For photon detection, superconducting transition-edge sensor(TES) micro-calorimeters are excellent energy-resolving devices. In this study, we report our recent work in developing Ti-/Au-based TES. The Ti/Au TES devic...For photon detection, superconducting transition-edge sensor(TES) micro-calorimeters are excellent energy-resolving devices. In this study, we report our recent work in developing Ti-/Au-based TES. The Ti/Au TES devices were designed and implemented with a thickness ratio of 1:1 and different suspended structures using micromachining technology. The characteristics were evaluated and analyzed, including surface morphology, 3 D deformation of suspended Ti/Au TES device structure, I–V characteristics, and low-temperature superconductivity. The results showed that the surface of Ti/Au has good homogeneity and the surface roughness of Ti/Au is significantly increased compared with the substrate. The structure of Ti/Au bilayer film significantly affects the deformation of suspended devices, but the deformation does not affect the I–V characteristics of the devices. For devices with the Ti/Au bilayer(150 μm × 150 μm) and beams(100 μm × 25 μm), the transition temperature(T;) is 253 m K with a width of 6 m K, and the value of the temperature sensitivity α is 95.1.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.51002081 and 61176119)
文摘For obtaining pure phase T12Ba2Ca2Cu3O10 (T1-2223) films with good superconducting properties, the growth technique is improved by dc magnetron sputtering and a triple post-annealing process. The triple post-annealing process comprises annealing twice in argon and once in oxygen at different temperatures. In the first low-temperature annealing phase in argon, T12Ba2CaCu2O8 (T1-2212) is obtained to effectively minimize evaporation in the next step. With the increase of temperature in the second annealing stage in argon, the previously prepared T1-2212 inter-phase is converted into T1-2223 phase. An additional annealing in oxygen is also adopted to improve the properties of T1-2223 films, each containing an optimal oxygen content value. The results of X-ray diffraction (XRD) θ-2θ scans, 09 scans and rotational φ scans show that each of the T1-2223 films has a high phase purity and an epitaxial structure. Smooth films are observed by scanning electron microscopy (SEM). The critical temperatures Tc of the films are measured to be about 120 K and the critical current densities Jc can reach 4.0 MA/cm2 at 77 K at self field.
基金Project supported by the National Natural Science Foundation of China(Grant No.51002081)the Fundamental Research Funds for the Central Universities,Chinathe Research Program of Application Foundation and Advanced Technology of Tianjin,China(Grant No.15JCQNJC01300)
文摘A new improved two-step method in fabricating Tl2Ba2 CaCu2O8(Tl-2212) thin films is presented in this paper. In the first process of dc magnetron sputtering, the thallium content in the precursor film is largely increased by adjusting the ratio of thallium in the sputtering targets. After the second annealing process in the absence of additional thallium pellets or powder source, high-quality Tl-2212 thin films can be obtained. The proper content of thallium in the precursor film provides a relatively stable atmosphere to guarantee the growth of Tl-2212 film. This method avoids the repeated production of the thallium pellets in the post-annealing process, the repeatability and controllability of the experiment are greatly improved. X-ray diffraction(XRD) scans show that all of the sharp peaks of the sample films can be assigned to the(00 l) peaks of Tl-2212 phase. The highest superconducting critical temperature(Tc) of the films is 105 K and the critical current density(Jc) can achieve 1.93 MA/cm2 in zero magnetic field at 77 K for a 600 nm film.
文摘Values of critieal eurrent densityJ。exceeding lo6A·em一2 at 77K and zerofield have been rePorted for thinmagnetlcfllnls ofYBaoCu:O,on sinZle ervstal substrates ofSrTIO:〔l一3)and一MgO(4,5)by manvfeseafCnerS.bllt tne rCSUltS OIJ、)IU一A’cm一IorY廿tU Illms on suoslrale 01 slngleerystal ZrO:(100)have not been found out inPublished PaPers 50 far.Owing to themierostrueture eharacters and highJ。ofYBCO films by contrast with bulk it 15 themost Possible to aPPly the fllms to eleetronicfield first.Therefore it 15 more signifieant toimProve values ofjcsubstrate with betterPIOCeSSJc>
文摘The rocking curve of Tl-2212 thin films in Fig.2 of our original paper[1]should be replaced with the following new one.Accordingly,in the fifth paragraph of Section 3 of the original paper,the statement“The full width at half maximum(FWHM)of the(0012)peak of the Tl-2212 phase is about 0.24°”should be“The full width at half maximum(FWHM)of the(0012)peak of the Tl-2212 phase is about 0.42°”.
基金the National Natural Science Foundation of China(Grant Nos.11653001 and 11653004)。
文摘Superconducting transition edge sensor(TES)bolometers require superconducting films to have controllable transition temperatures T_(c)in different practical applications.The value of T_(c)strongly affects thermal conductivity and thermal noise performance of TES detectors.Al films doped with Mn(Al-Mn)of different concentrations can accomplish tunable T_(c)A magnetron sputtering machine is used to deposit the Al-Mn films in this study.Fabrication parameters including sputtering pressure and annealing process are studied and their influences on T_(c)and superconducting transition widthΔT_(c)are optimized.The Al-Mn films withΔT_(c)below 1.0 mK for T_(c)in a range of 520 mK-580 mK are successfully fabricated.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11925304 and 12020101002)the Chinese Academy of Sciences Program(Grant No.GJJSTD20210002).
文摘Disordered superconducting materials like NbTiN possess a high kinetic inductance fraction and an adjustable critical temperature, making them a good choice for low-temperature detectors. Their energy gap(D), critical temperature(T_(c)),and quasiparticle density of states(QDOS) distribution, however, deviate from the classical BCS theory due to the disorder effects. The Usadel equation, which takes account of elastic scattering, non-elastic scattering, and electro–phonon coupling,can be applied to explain and describe these deviations. This paper presents numerical simulations of the disorder effects based on the Usadel equation to investigate their effects on the △, Tc, QDOS distribution, and complex conductivity of the NbTiN film. Furthermore, NbTiN superconducting resonators with coplanar waveguide(CPW) structures are fabricated and characterized at different temperatures to validate our numerical simulations. The pair-breaking parameter α and the critical temperature in the pure state T_(c)^(P) of our NbTiN film are determined from the experimental results and numerical simulations. This study has significant implications for the development of low-temperature detectors made of disordered superconducting materials.
基金Project supported by the National Key Basic Research Program of China(Grant Nos.2021YFA0718700,2018YFB0704102,2017YFA0303003,2017YFA0302902,2016YFA0300301,and 2021YFA0718802)the National Natural Science Foundation of China(Grant Nos.11927808,11834016,118115301,119611410,11961141008,61727805+5 种基金11961141002)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(CAS)(Grant Nos.QYZDB-SSW-SLH008 and QYZDY-SSW-SLH001)CAS Interdisciplinary Innovation Team,the Strategic Priority Research Program(B)of CAS(Grant Nos.XDB25000000and XDB33000000)the Beijing Natural Science Foundation(Grant No.Z190008)the Key-Area Research and Development Program of Guangdong Province,China(Grant No.2020B0101340002)the support from the China Postdoctoral Science Foundation(Grant No.2022M711497)。
文摘High quality Nb films were successfully prepared on both flexible polyimide(PI)and rigid Al2O3substrates and their transport properties were systematically studied at various applied currents,external magnetic fields,and sample orientations.It is found that a curved Nb/PI film exhibits quite different superconducting transition and vortex dynamics compared to the flat Nb/Al2O3film.For the curved Nb/PI film,smooth superconducting transitions were obtained at low currents,while unexpected cascade structures were revealed in theρ(T)curves at high currents.We attribute this phenomenon to the gradient distribution of vortex density together with a variation of superconductivity along the curved film.In addition,reentrant superconductivity was induced in the curved Nb/PI thin film by properly choosing the measurement conditions.We attribute this effect to the vortex pinning from both in-plane vortices and out-of-plane vortices.This work reveals the complex transport properties of curved superconducting thin films,providing important insights for further theoretical investigations and practical developments of flexible superconductors.
基金Project supported by the National Basic Research Program of China(Grant Nos.2006CB921107 and 2010CB630704)the National Natural Science Foundation of China(Grant No.10774165)
文摘We find that the superconductivity in the thin films of the formerly believed non-superconducting parent compound FeTe is accompanied by an emergence of second order with a correlation length of 742 nm and 258 nm at 10 K and 300 K, respectively. The structural phase transition found in iron pnictide superconductors, in non-superconducting FeTe bulk samples, and in FeSe superconducting thin films is not observed in the superconducting FeTe thin films. The interplay between superconductivity and long range order may suggest the crucial role of competition between electronic localization and itinerancy which leads to strong quantum fluctuations in the FeTe system.
文摘The patterning technologies and process order of high Tc(86K) super-conducting film bolometers have been studied. After the deposition, a conventional lithographic process was used to pattern the films with aqueous solution of HCl, and then the films were transferred into a tube furnace for annealing to form superconducting film. It eliminates the degradation of patterning process. The bolometric responsivity of approximately 34. 32 V/W is measured, and the detectivity is greater than 1. 62× 108cm · Hz1/2 · W-1, the noise equivalent powers NEP is 2. 1×10-9W.
文摘Laser ablated high temperature superconducting and related thin films are investigated with a microscopical point of view.The microstructure and microchemistry of three thin films(Y-Ba-Cu-O, Bi-Pb-Sr-Ca-Cu-O and Sr-Ca-Cu-O)are demonstrated as examples of laser ablation products.
基金Supported by the National Natural Science Foundation of China under Grant No 11104331the National Basic Research Program of China under Grant No 2011CB921702
文摘Systemic measurements show that there is no 3D to 2D crossover in the reduction of the superconducting transition temperature Tc in Nb thin films. This result is consistent with all previous measurements while it is contrary to the prevailing understanding based on the interplay between proximity, localization, and lifetime broadening. Our study indicates that the decrease of Tc can be interpreted by the combined effects of electron-phonon coupling parameter λ and the defect scattering rate pw, being uniquely determined by their ratio λ/ρw. Other factors such as film thickness and irradiation do not produce additional effects beyond these two parameters.
基金Project supported by the National Natural Science Foundation of China (Grant No. 12174242)the National Key Research and Development Program of China (Grant No. 2018YFA0704300)+1 种基金the Key Research Project of Zhejiang Laboratory (Grant No. 2021PE0AC02)the support by the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning
文摘Multicomponent superconductors exhibit nontrivial vortex behaviors due to the various vortex–vortex interactions,including the competing one in the recently proposed type-1.5 superconductor.However,potential candidate that can be used to study the multicomponent superconductivity is rare.Here,we prepared an artificial superconducting multilayer to act as an alternative approach to study multicomponent superconductivity.The additional repulsive length and the coupling strength among superconducting films were regulated by changing the thickness of the insulting layer.The magnetization measurements were performed to clarify the effect of the competition between the repulsive vortex interactions on the macroscopic superconductivity.The vortex phase diagram and the optimum critical current density have been determined.Furthermore,a second magnetization effect is observed,and is attributed to the upper layer,which provides the weak pinning sites to localize the flux lines.The pinning behaviors switches to the mixed type with the increase of the insulting layer thicknesses.Our results open a new perspective to the study and related applications of the multilayer superconducting systems.
基金Project supported by the National Natural Science Foundation of China (Grant No 10474121).
文摘YBa2Cu3O7(YBCO) thin films have been prepared by thermal coevaporation on LaAlO3(LAO) substrates, and Tl2Ba2CaCu2O8(TBCCO) thin films are synthesized by magnetron sputtering method on LAO substrates. The transition temperature Tc is 90 K forYBCO/LAO and 104 K for TBCCO/LAO. Microwave responses of the films are studied systematically by coplanar resonator technique. Energy gaps of the films obtained are △0 = 1.04kBTc for YBCO films and △0 =0.84kBTc for TBCCO films by analysing the temperature dependence of resonant frequencies of coplanar resonator. Penetration depth at 0 K A0 = 198.nm for YBCO films and A0 = 200 nm for TBCCO films could also be obtained by using the weak coupling theory and two fluid theory. Results of penetration depth and energy gap confirm the weak coupling properties of the films. In addition, microwave surface resistances Rs of YBCO/LAO and TBCCO/LAO are also investigated by analysing the quality factor and insert loss of the coplanar resonator. Surface resistance of TBCCO/LAO is less than that of YBCO/LAO, so that TBCCO/LAO films may have more potential applications.
基金supported by the National Natural Science Foundation of Chinathe National Basic Research Program of China
文摘Our recent progress in the fabrication of FeSe and KxFe2_ySe2 ultra thin films and the understanding of their superconductivity properties is reviewed. The growth of high-quality FeSe and KxFe2_ySe2 films is achieved in a well controlled manner by molecular beam epitaxy. The high-quality stoichiometric and superconducting crystalline thin films allow us to investigate the intrinsic superconductivity properties and the interplay between the superconductivity and the film thickness, the local structure, the substrate, and magnetism. In situ low-temperature scanning tunneling spectra reveal the nodes and the twofold symmetry in FeSe, high-temperature superconductivity at the FeSe/SrTiO3 interface, phase separation and magnetic order in KxFe2_ySe2, and the suppression of superconductivity by twin boundaries and Fe vacancies. Our findings not only provide fundamental information for understanding the mechanism of unconventional superconductivity, but also demonstrate a powerful way of engineering superconductors and raising the transition temperature.
文摘High quality epitaxial YBa2Cu3O7-δ (YBCO) superconducting films were fabricated on (00l) LaAlO3 substrates using the direct-current sputtering method. The attainment of an unusually high film thickness (up to 2.0 μm) without mi-crocracking was attributed in part to the presence of pores correlated with yttrium-rich composition in the films. The influ-ence of the film thickness on the microstructure was investigated by X-ray diffraction conventional scan (θ-2θ,ω-scan,pole figure) and high-resolution reciprocal space mapping. The films were c-axis oriented with no a-axis-oriented grains up to the thickness of 2 μm. The surface morphology and the critical current density (Jc) strongly depended on the film thickness. Furthermore,the reasons for these thickness dependences were elucidated in detail.
文摘Large area YBCO superconductive films prepared by d.c. magnetron sputtering have reached: T c>89 K, J c>3.5×10 6 A/cm 2 (77 K, 0 T), R s=0.25 mΩ, at 77.5 K, 9894 MHz. The microstructure analysis of the film showed it has fine monocrystalline structure and the crystalline perfectness is satisfactory. The oscillator, filter and antenna made from these films are good in performance. Therefore, YBCO superconductive films have great prospect in application.
基金supported by the National Basic Research Program of China(Grant Nos.2013CB921902 and 2011CB922200)the National Natural Science Foundation of China(Grant Nos.11227404,11274228,11521404,11174199,and 11134008)
文摘The discovery of an extraordinarily superconductive large energy gap in SrTiO3 supported single-layer FeSe films has recently initiated a great deal of research interests in surface-enhanced superconductivity and superconductive ultrathin films fabricated on crystal surfaces. On account of the instability of ultra-thin films in air, it is desirable to perform elec- trical transport measurement in ultra-high vaccum (UHV). Here we review the experimental techniques of in situ electrical transport measurement and their applications on superconductive ultrathin films.
基金Project supported by the Comsats Institute of Information Technology, Islamabad, Pakistan,the National Natural Science Foundation of China (Grant No 10674168)the State Key Program for Basic Research of China (Grant No 2006CB601006)
文摘A square hole array is fabricated over a micro-bridge of NbN thin film by electron beam lithography and reactive ion milling. Magneto-resistance is measured across the micro-bridge filled with a hole array near the superconducting transition temperature. It is found that magneto-resistance minima occur when the number of vortices is an integer multiple or a fractional multiple of the number of holes. The temperature and the current dependences of the matching effect are studied.
基金partially supported by the Natural Science Foundation of China (Nos. 19971030, 10471050)the Natural Science Foundation of Guangdong Province (No. 000671, No. 031495)partially supported by a grant from HKRGC
文摘In this paper, we discuss the vortex structure of the superconducting thin films placed in a magnetic field. We show that the global minimizer of the functional modelling the superconducting thin films has a bounded number of vortices when the applied magnetic field hex 〈 Hc1 + K log | logε| where Hc1 is the lower critical field of the film obtained by Ding and Du in SIAM J. Math. Anal., 2002. The locations of the vortices are also given.
文摘For photon detection, superconducting transition-edge sensor(TES) micro-calorimeters are excellent energy-resolving devices. In this study, we report our recent work in developing Ti-/Au-based TES. The Ti/Au TES devices were designed and implemented with a thickness ratio of 1:1 and different suspended structures using micromachining technology. The characteristics were evaluated and analyzed, including surface morphology, 3 D deformation of suspended Ti/Au TES device structure, I–V characteristics, and low-temperature superconductivity. The results showed that the surface of Ti/Au has good homogeneity and the surface roughness of Ti/Au is significantly increased compared with the substrate. The structure of Ti/Au bilayer film significantly affects the deformation of suspended devices, but the deformation does not affect the I–V characteristics of the devices. For devices with the Ti/Au bilayer(150 μm × 150 μm) and beams(100 μm × 25 μm), the transition temperature(T;) is 253 m K with a width of 6 m K, and the value of the temperature sensitivity α is 95.1.