基于LSAT衬底YBa_(2)Cu_(3)O_(7)-δ台阶结的射频高温超导量子干涉器的制备和表征  

Fabrication and Characterization of YBa_(2)Cu_(3)O_(7-δ) Radio Frequency SQUIDs with Step-edge Josephson Junctions on LSAT Substrates

作　　者：王家明 李宇龙 王宏章 徐铁权 马平[1] 王越[1] WANG Jiaming;LI Yulong;WANG Hongzhang;XU Tiequan;MA Ping;WANG Yue(State Key Laboratory for Mesoscopic Physics,Applied Superconductivity Center,School of Physics,Peking University,Beijing 100871,China)

机构地区：[1]北京大学物理学院,北京大学应用超导研究中心,人工微结构和介观物理国家重点实验室,北京100871

出　　处：《低温物理学报》2021年第2期89-97,共9页Low Temperature Physical Letters

基　　金：Project supported by the National Key Research and Development Program of China(Grant No.2017YFC0601900);the National Natural Science Foundation of China(Grant No.61571019).

摘　　要：基于YBa_(2)Cu_(3)O_(7)-δ(YBCO)台阶边沿型约瑟夫森结(台阶结)的高温超导量子干涉器(Superconducting Quantum Interference Device,简称SQUID)在微弱磁场测量等领域具有重要应用价值.制备YBCO台阶结及SQUID的常用单晶衬底包括LaAlO_(3)(LAO)、SrTiO_(3)(STO)及MgO等.(La_(0.3),Sr_(0.7))(Al_(0.65),Ta_(0.3)5)O_(3)(LSAT)没有孪晶现象、与YBCO的晶格失配度很小(仅为0.4%),有潜力成为制备YBCO台阶结及相应的高温超导SQUID器件的新的衬底选择.本文首次探索研究了LSAT衬底上YBCO台阶结型射频超导量子干涉器(rf SQUID)的制备和表征.采用氩离子束刻蚀技术在LSAT(100)衬底上制备角度约为46°的台阶,利用脉冲激光沉积法在衬底上生长YBCO超导薄膜,然后利用传统紫外光刻技术制备出高温超导rf SQUID器件.在温度为77 K时,器件测试观察到幅度较大的电压-磁通特性曲线,且在部分器件的特性曲线中观察到接近方波的非传统波形,表明器件工作于噪声较低的色散模式下.频率1 kHz时器件的磁通噪声约为20μΦ0/Hz1/2,与文献中报道的LAO、STO衬底上台阶结型SQUID器件的典型结果相当.本工作展示了利用LSAT衬底制备低噪声台阶结型rf SQUID器件的可行性,并为进一步研制该衬底上更高性能的高温超导SQUID器件奠定了基础.YBa_(2)Cu_(3)O_(7)-δ(YBCO)superconducting quantum interference devices(SQUIDs)with step-edge junctions(SEJs)have many important applications in detection of various weak magnetic signals.(La_(0.3),Sr_(0.7))(Al_(0.65),Ta_(0.3)5)O_(3)(LSAT),having very close lattice match with YBCO and no twinning property,is a prospective substrate to be employed in the fabrication of YBCO SEJ SQUIDs,besides the commonly-used substrates like LaAlO_(3)(LAO)and SrTiO_(3)(STO).In this paper we explored for the first time the fabrication and characterization of YBCO SEJ SQUIDs on LSAT(100)substrate.Steps showing an edge angle of about 46°were produced on LSAT substrate by an argon ion beam milling.With subsequent pulsed-laser deposition of YBCO thin film and conventional photolithography,radiofrequency(rf)SQUIDs were fabricated.At77 K,the device works in then on hysteretic regime with recommended conditions fulfilled,as indicated by the nearly rectangular waveform of the voltage-flux characteristics.The magnetic flux noise of the device is about 20μΦ0/Hz1/2 at 1 kHz,comparable to the values as typically reported for devices on LAO and STO substrates.The present results demonstrate the feasibility of fabricating low-noise rf SQUIDs with YBCO SEJs on LSAT substrate.

关 键 词：YBa_(2)Cu_(3)O_(7) -δ 台阶结 超导量子干涉器 LSAT 

分 类 号：TH744.3[机械工程—光学工程]