YBa_(2)Cu_(3)O_(7-δ)薄膜微结构的同步辐射三维倒空间扫描研究

Microstructure study of YBa_(2)Cu_(3)O_(7-δ) thin film with synchrotron-based three-dimensional reciprocal space mapping

高温超导薄膜因其微波表面电阻低,可用于尖端高温超导微波器件的制作.然而由于高温超导材料特殊的二维超导机制和极短的超导相干长度,高温超导材料的微波表面电阻对微结构特别敏感.为了探究高温超导材料微结构和微波电阻的联系,采用脉冲激光沉积(PLD)技术在(001)取向的MgO单晶衬底上生长了不同厚度的YBa_(2)Cu_(3)O_(7-δ)(YBCO)薄膜.电学测量发现不同厚度的样品超导转变温度、常温电阻差别不大,但超导态的微波表面电阻差异很大.同步辐射三维倒空间扫描(3D-RSM)技术对YBCO薄膜微结构的表征表明:CuO_(2)面平行于表面晶粒(c晶)的多寡、晶粒取向的一致性是造成超导态微波表面电阻差异的主要原因.

High-temperature superconducting films can be used for fabricating the cutting-edge high-temperature superconducting microwave devices because of their low microwave surface resistances.However,the microwave surface resistances of high-temperature superconducting materials are particularly sensitive to microstructure due to their special two-dimensional superconducting mechanisms and extremely short superconducting coherence lengths.To investigate the correlations between microstructure and microwave surface resistance of high-temperature superconducting materials,YBa_(2)Cu_(3)O_(7-δ)(YBCO) films with different thickness are grown on(001)-oriented MgO single-crystal substrates by using the pulsed laser deposition(PLD) technique.Electrical measurements reveal that their superconducting transition temperatures and room temperature resistances do not show significant difference.However,their microwave surface resistances in superconducting state display a significant difference.The characterizations of the microstructures of YBCO films by synchrotron radiation three-dimensional reciprocal space mapping(3D-RSM) technique show that the number of the grains with CuO_(2)face parallel to the surface(c crystals),and the consistency of grain orientation are the main causes for the difference in microwave surface resistance.