采用RDL100型电子高温蠕变试验机测试了新型Cr18Ni9Nb Ti N奥氏体不锈钢在650℃不同应力下的蠕变性能。利用SEM、TEM及EDS等观察分析了220 MPa下不同蠕变阶段的组织形貌。结果表明,蠕变初期,晶内位错密度急剧增加,位错发生缠结,晶内有...采用RDL100型电子高温蠕变试验机测试了新型Cr18Ni9Nb Ti N奥氏体不锈钢在650℃不同应力下的蠕变性能。利用SEM、TEM及EDS等观察分析了220 MPa下不同蠕变阶段的组织形貌。结果表明,蠕变初期,晶内位错密度急剧增加,位错发生缠结,晶内有细小的Nb N相弥散析出;稳态蠕变阶段,位错形成网状结构,晶内有Ti N颗粒析出,链状(Cr,Fe)23C6沿晶界析出,位错网和析出的第二相共同降低了位错可动性,改善了合金抗蠕变性能;加速蠕变阶段,大量扩展位错出现,延长了蠕变寿命。Cr18Ni9Nb Ti N钢蠕变断裂属于沿晶脆性断裂,晶界处发现部分(Cr,Fe)23C6剥落,三叉晶界处发现楔形裂纹。展开更多
NbTiN thin films are good candidates for applications including single-photon detector, kinetic inductance detector, hot electron bolometer, and superconducting quantum computing circuits because of their favorable ch...NbTiN thin films are good candidates for applications including single-photon detector, kinetic inductance detector, hot electron bolometer, and superconducting quantum computing circuits because of their favorable characteristics,such as good superconducting properties and easy fabrication.In this work, we systematically investigated the growth of high-quality NbTiN films with different thicknesses on Si substrates by reactive DC-magnetron sputtering method.After optimizing the growth conditions, such as the gas pressure, Ar/N2 mixture ratio, and sputtering power, we obtained films with excellent superconducting properties.A high superconducting transition temperature of 15.5 K with narrow transition width of 0.03 K was obtained in a film of 300 nm thickness with surface roughness of less than 0.2 nm.In an ultra-thin film of 5 nm thick, we still obtained a transition temperature of 7.6 K.In addition, rapid thermal annealing(RTA) in atmosphere of nitrogen or nitrogen and hydrogen mixture was studied to improve the film quality.The results showed that Tc and crystal size of the NbTiN films were remarkably increased by RTA.For ultrathin films, the annealing in N2/H2 mixture had better effect than that in pure N2.The Tc of 10 nm films improved from 9.6 K to 10.3 K after RTA in N2/H2 mixture at 450℃.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
We study superconducting properties of NbN thin film samples with different thicknesses and an ultra-thin NbTiN meander nanowire sample.For the ultra-thin samples,we found that the temperature dependence of upper crit...We study superconducting properties of NbN thin film samples with different thicknesses and an ultra-thin NbTiN meander nanowire sample.For the ultra-thin samples,we found that the temperature dependence of upper critical field(Hc2)in parallel to surface orientation shows bending curvature close to critical temperature Tc,suggesting a two-dimensional(2D)nature of the samples.The 2D behavior is further supported by the angular dependence measurements of Hc2 for the thinnest samples.The temperature dependence of parallel upper critical field for the thick films could be described by a model based on the anisotropic Ginzburg-Landau theory.Interestingly,the results measured in the field perpendicular to the film surface orientation show a similar bending curvature but in a much narrow temperature region close to Tc for the ultra-thin samples.We suggest that this feature could be due to suppression of pair-breaking caused by local in-homogeneity.We further propose the temperature dependence of perpendicular Hc2 as a measure of uniformity of superconducting ultra-thin films.For the thick samples,we find that Hc2 shows maxima for both parallel and perpendicular orientations.The Hc2 peak for the perpendicular orientation is believed to be due to the columnar structure formed during the growth of the thick films.The presence of columnar structure is confirmed by transmission electron microscopy(TEM).In addition,we have measured the angular dependence of magneto-resistance,and the results are consistent with the Hc2 data.展开更多
文摘采用RDL100型电子高温蠕变试验机测试了新型Cr18Ni9Nb Ti N奥氏体不锈钢在650℃不同应力下的蠕变性能。利用SEM、TEM及EDS等观察分析了220 MPa下不同蠕变阶段的组织形貌。结果表明,蠕变初期,晶内位错密度急剧增加,位错发生缠结,晶内有细小的Nb N相弥散析出;稳态蠕变阶段,位错形成网状结构,晶内有Ti N颗粒析出,链状(Cr,Fe)23C6沿晶界析出,位错网和析出的第二相共同降低了位错可动性,改善了合金抗蠕变性能;加速蠕变阶段,大量扩展位错出现,延长了蠕变寿命。Cr18Ni9Nb Ti N钢蠕变断裂属于沿晶脆性断裂,晶界处发现部分(Cr,Fe)23C6剥落,三叉晶界处发现楔形裂纹。
基金Project supported by the Chinese Academy of Sciences Strategic Priority Research Program B(Grant No.XDB07010300)the National Natural Science Foundation of China(Grant No.11674376)
文摘NbTiN thin films are good candidates for applications including single-photon detector, kinetic inductance detector, hot electron bolometer, and superconducting quantum computing circuits because of their favorable characteristics,such as good superconducting properties and easy fabrication.In this work, we systematically investigated the growth of high-quality NbTiN films with different thicknesses on Si substrates by reactive DC-magnetron sputtering method.After optimizing the growth conditions, such as the gas pressure, Ar/N2 mixture ratio, and sputtering power, we obtained films with excellent superconducting properties.A high superconducting transition temperature of 15.5 K with narrow transition width of 0.03 K was obtained in a film of 300 nm thickness with surface roughness of less than 0.2 nm.In an ultra-thin film of 5 nm thick, we still obtained a transition temperature of 7.6 K.In addition, rapid thermal annealing(RTA) in atmosphere of nitrogen or nitrogen and hydrogen mixture was studied to improve the film quality.The results showed that Tc and crystal size of the NbTiN films were remarkably increased by RTA.For ultrathin films, the annealing in N2/H2 mixture had better effect than that in pure N2.The Tc of 10 nm films improved from 9.6 K to 10.3 K after RTA in N2/H2 mixture at 450℃.
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the Chinese Academy of Sciences(Grant No.XDB25000000).
文摘We study superconducting properties of NbN thin film samples with different thicknesses and an ultra-thin NbTiN meander nanowire sample.For the ultra-thin samples,we found that the temperature dependence of upper critical field(Hc2)in parallel to surface orientation shows bending curvature close to critical temperature Tc,suggesting a two-dimensional(2D)nature of the samples.The 2D behavior is further supported by the angular dependence measurements of Hc2 for the thinnest samples.The temperature dependence of parallel upper critical field for the thick films could be described by a model based on the anisotropic Ginzburg-Landau theory.Interestingly,the results measured in the field perpendicular to the film surface orientation show a similar bending curvature but in a much narrow temperature region close to Tc for the ultra-thin samples.We suggest that this feature could be due to suppression of pair-breaking caused by local in-homogeneity.We further propose the temperature dependence of perpendicular Hc2 as a measure of uniformity of superconducting ultra-thin films.For the thick samples,we find that Hc2 shows maxima for both parallel and perpendicular orientations.The Hc2 peak for the perpendicular orientation is believed to be due to the columnar structure formed during the growth of the thick films.The presence of columnar structure is confirmed by transmission electron microscopy(TEM).In addition,we have measured the angular dependence of magneto-resistance,and the results are consistent with the Hc2 data.
