Single phase, c-axis oriented, e-doped, Sr1-xLaxCuO2 thin films were epitaxially grown on KTaO3 and DyScO3 substrates by reactive rf sputtering. As-grown films being insulating due to oxygen excess, oxygen reduction is necessary to observe superconductivity. Two different procedures were employed to reach superconductivity. On one hand an in-situ reduction process was conducted on a series of films deposited on both types of substrates. On the other hand, an ex-situ reduction procedure was performed sequentially on a single film deposited on DyScO3. The study of the influence of oxygen reduction on the structural and electronic properties of the thin films is presented and discussed.
Differentiation of electron doping and oxygen reduction in electron-doped cuprates
Institute for Solid State Physics, The University of Tokyo（东京大学固体离子体研究所）；Department of Engineering and Applied Sciences, Sophia University（上智大学理工学部）；Department of Applied Physics, Tohoku University（东北大学应用物理系）；UVSOR Synchrotron Facility, Institute for Molecular Science（分子科学研究所UVSOR同步辐射设施）
Electron-doped and hole-doped superconducting cuprates exhibit a symmetric phase diagram as a function of doping. This symmetry is however only approximate. Indeed, electron-doped cuprates become superconductors only after a specific annealing process: This annealing affects the oxygen content by only a tiny amount, but has a dramatic impact on the electronic properties of the sample. Here we report the occurrence of superconductivity in oxygen-deficient Nd$_{2-x}$Ce$_x$CuO$_4$ thin films grown in an oxygen-free environment, after annealing in pure argon flow. As verified by x-ray diffraction,…
Sr-doped Bi2Se3 thin films was known as a potential candidate of topological superconductor. The magnetoresistance (MR) of SrxBi2Se3 films with various doping concentrations x were found to be dominated by weak antilocalization (WAL) at low magnetic fields, whereas the classical MR, which originally dominated the MR, was almost completely suppressed. In contrast, the MR of all samples has been observed to be dominated by linear magnetoresistance (LMR) at high magnetic fields. The LMR, having the linear dependence on carrier mobility, can be successfully explained by the Parish-Littlewood model…
The effects of oxygen in spinel oxide Li1+xTi2-xO4-delta thin films
通过在样品制备过程中精确调节氧分压，研究了从超导LiTi_2 O_4-δ到绝缘Li_4 Ti_5 O_（12）薄膜的演变过程。在LiTi 2 O 4-delta超导薄膜中，随着氧分压的增加，氧空位被填充，c轴晶格常数逐渐减小。随着氧分压的增加，c轴晶格常数趋于稳定，Li 4 Ti 5 O 12相开始形成。充氧过程由扫描透射电子显微镜技术的角度明场图像显示。随着氧分压的增加，磁电阻温度的正负变化呈现出非单调的变化规律。本文还讨论了氧对LiTi_2 O_4-δ结构和超导电性影响的理论解释。
Novel nanoscale probes are opening new venues for understanding unconventional electronic and magnetic functionalities driven by multiscale lattice complexity in doped high temperature superconducting perovskites. In this work we focus on the multiscale texture at supramolecular level of atomic oxygen interstitials (O-i) stripes in HgBa$_2$CuO$_{4+y}$ at optimal doping for the highest superconducting critical temperature $T_C$=94K. We report compelling evidence for the nematic phase of oxygen-interstitial O-i atomic wires with fractal-like spatial distribution over multiple scales by using sca…
Superconductivity Induced in Iron Telluride Films by Low Temperature Oxygen Incorporation
我们报告的超导诱导膜的非超导，反铁磁母体材料FeTe的低温氧掺入在可逆的方式。X射线吸收表明，氧掺杂改变了名义Fe价态从2+在非超导状态，主要是3+在超导状态。因此，氧掺杂的FeTe中的超导性发生在与更常见的FeTe $_{1-x}$ Se $_x$完全不同的电荷和应变状态下。这项工作也提出了一个方便的路径进行掺杂实验原位与许多测量技术。
Impact of Oxygen Diffusion on Superconductivity in YBa$_2$Cu$_3$O$_{7-δ}$ Thin Films Studied by Positron Annihilation Spectroscopy
$_2$ O $_{7-δ}$（YBCO）中的氧缺陷$δ$对高温超导性起着至关重要的作用。本文利用电子正电子湮没线的多普勒展宽谱（符合谱）原位研究了生长在SrTiO $_3$（STO）衬底上的YBCO单晶薄膜中氧浓度及其深度分布的温度依赖性。发现回火过程中的氧扩散导致$δ$的明显深度依赖性，这是使用X射线衍射无法获得的。在几分钟内达到的稳态由表面处和与STO基底的界面处的氧交换限定。此外，我们揭示了深度依赖的临界温度$T_{\mathrm{c}}$在制备和回火的YBCO薄膜。
We investigated chemical pressure effects in electron-doped (e-doped) FeSe by fabricating an electric-double-layer structure with single crystalline FeSe films on LaAlO$_3$ with Se substituted by isovalent Te and S. Our method enables transport measurements of e-doped FeSe. Electron doping by applying gate voltage of 5 V increases $T_{\mathrm c}$ of the FeSe$_{1-x}$Te$_x$ and FeSe$_{1-y}$S$_y$ films with $0 \leq x \leq 0.4$ and $0 \leq y \leq 0.25$, while the e-doped $x=0.5$ film showed lower $T_{\mathrm c}$ than that of the undoped one. Both positive and chemical pressure suppress $T_{\mathrm…
Molecular beam epitaxy of K-doped Ba122 (Ba$_{1-x}$K$_x$Fe$_\text{2}$As$_\text{2}$) superconductor was realized on a MgO substrate. Microstructural observation revealed that the undoped Ba122 served as a perfect buffer layer for epitaxial growth of the K-doped Ba122. The film exhibited a high critical temperature of 39.8 K and a high critical current density of 3.9 MA/cm$^\text{2}$ at 4 K. The successful growth of epitaxial thin film will enable artificial single grain boundary on oxide bicrystal substrates and reveal the grain boundary transport nature of K-doped Ba122.
Atomically-flat, chemically-stable, superconducting epitaxial thin film of iron-based superconductor, cobalt-doped BaFe$_2$As$_2$
最近报道了诸如Co掺杂的SrFe $_2$ As $_2$（SrFe $_2$ As $_2$：Co）的Fe基超导体的外延生长，但是由于它们具有粗糙的表面并且通过与环境大气中的水蒸气的反应而分解，因此对于器件应用而言仍然具有不足的性能。本文报道了在700 ℃下生长的Co掺杂BaFe $_2$ As $_2$外延膜的超导转变起始温度为20 K。该转变比在SrFe $_2$ As $_2$：Co膜上观察到的转变更尖锐，这将源于它们改进的结晶度。这些薄膜还具有原子级平坦的表面，具有台阶和露台结构，并表现出抗水蒸气暴露的化学稳定性。
Boron-doped diamond granular thin films are known to exhibit superconductivity with an optimal critical temperature of Tc = 7.2K. Here we report the measured complex surface impedance of Boron-doped diamond films in the microwave frequency range using a resonant technique. Experimentally measured inductance values are in good agreement with estimates obtained from the normal state sheet resistance of the material. The magnetic penetration depth temperature dependence is consistent with that of a fully-gapped s-wave superconductor. Boron-doped diamond films should find application where high ki…
Stabilizing and Tuning Superconductivity in La$_3$Ni$_2$O$_{7-δ}$ Films: Oxygen Recycling Protocol Reveals Hole-Doping Analogue
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所凝聚态物理国家实验室）；University of Chinese Academy of Sciences（中国科学院大学）；Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Sciences（中国科学院上海高等研究院上海同步辐射光源）；Beijing Academy of Quantum Information Sciences（北京量子信息科学研究院）；Songshan Lake Materials Laboratory（松山湖材料实验室）
