Surface Impedance of YBa2Cu3O7−δ Films Grown on MgO Substrate as a Function of Film Thickness
Surface Impedance of YBa2Cu3O7−δ Films Grown on MgO Substrate as a Function of Film Thickness
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DOI：
10.1007/s10948-012-1695-x
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发表时间：
2013
影响因子：
1.8
通讯作者：
A. Barannik;N. Cherpak;M. S. Kharchenko;R. Semerad;S. Vitusevich
中科院分区：
文献类型：
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作者：
A. Barannik;N. Cherpak;M. S. Kharchenko;R. Semerad;S. Vitusevich
采用基于单晶蓝宝石制造的 Ka 波段回音壁模式 (WGM) 介质谐振器 (DR) 的测量技术，研究了通过磁控管热共蒸发在单晶 MgO 衬底上制备的厚度 df= 75、150、300、600 nm 的外延 YBa2Cu3O7−δ 薄膜的表面阻抗特性。在 20 K 至 90 K 的温度范围内对未图案化薄膜进行表征。结果表明，有效表面电阻接近最小值（df>300 nm）。同时，固有阻抗特性实际上与所研究的 df 值区间无关。伦敦穿透深度的温度依赖性通过实验估计并用模型表达式近似。所有薄膜（除 75 nm 厚度的薄膜外）在制造一年后，在低温下表面电阻降低约两倍的效果均得到记录。这种效应可以通过薄膜光过度掺杂后薄膜参数随时间的变化来解释。
The surface impedance characteristics of epitaxial YBa2Cu3O7−δfilms of thicknessdf= 75, 150, 300, 600 nm, produced by magnetron thermal co-evaporation onto single crystal MgO substrates was studied using measurement technique based on Ka-band whispering gallery mode (WGM) dielectric resonator (DR) fabricated from single crystal sapphire. Characterization of the unpatterned films was carried out in temperature interval from 20 K to 90 K. It was shown that the effective surface resistance approaches the minimum value fordf>300 nm. At the same time, intrinsic impedance properties are practically independent ondfin the studied interval ofdfvalues. The temperature dependence of London penetration depth was estimated experimentally and approximated with the model expressions. Effect of reducing the surface resistance of approximately two times at low temperatures one year later after their manufacture was registered for all films(except the film of 75 nm thickness). The effect may be explained by changes of the film parameters in time after the film light overdoping.