High quality superconducting thin films are the basis for the application of superconducting devices. Here, we report on the film growth and superconducting properties of Ta films. The films were grown by the pulsed laser deposition technique on the α-Al₂O₃ substrates. It is found that, with the increase of the film thickness from 20 nm to 61 nm, both the superconducting transition temperature Tc and residual resistance ratio (RRR) display an upward trend, while the upper critical field decreases monotonously in a wide temperature region. A clear anisotropic behavior is revealed by comparing the upper critical fields with two different orientations ( H⊥film and H∥film ). The anisotropy parameter Γ is found to be as high as 20 for the sample with the thickness of 20 nm. The systematical evolution from two- to three-dimensional features for the superconductivity with increasing the film thickness is observed in the temperature dependent upper critical field data. Moreover, the vortex liquid region tends to expand with the increase in the film thickness.

中文翻译：

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PLD 生长的 Ta 薄膜上临界场和超导涡旋相随厚度的演变

高质量的超导薄膜是超导器件应用的基础。在这里，我们报告了 Ta 薄膜的薄膜生长和超导特性。这些薄膜是通过脉冲激光沉积技术在α-Al ₂ O ₃基材。研究发现，随着薄膜厚度从 20 nm 增加到 61 nm，超导转变温度 吨C 和剩余电阻比（RRR）呈上升趋势，而上临界场在宽温度范围内单调下降。通过比较具有两个不同方向的上临界场，揭示了明显的各向异性行为（ H⊥电影 和 H∥电影 ). 对于厚度为 20 nm 的样品，发现各向异性参数 Γ 高达 20。在依赖于温度的上临界场数据中观察到随着薄膜厚度的增加，超导性从二维到三维特征的系统演化。此外，旋涡液体区域随着膜厚的增加而趋于扩大。