垂直式三明治YBCO/CeO2/YBCO超導量子干涉元件之製作與特性研究

Abstract

本研究探討了一種垂直式三明治之超導量子干涉元件(SQUID)製作方法。使用射頻磁控濺鍍方式成長釔鋇銅氧(YBa2Cu3O7-δ)/二氧化鈰(CeO2)/釔鋇銅氧(YBa2Cu3O7-δ)三層膜於鈦酸鍶(SrTiO3)基板上，以光學微影及離子蝕刻方式製作垂直式三明治結構之超導量子干涉元件，並且量測出SQUID的特性曲線，作為一可能取代雙晶基板製作SQUID元件之替代方案。 由量測結果得知，回收的鈦酸鍶單晶基板經過拋光研磨技術讓基板表面粗糙度降至0.6 nm，可用於成長高品質的高溫超導薄膜。製作完的SQUID元件在77 K時有剩餘電阻的情況，但是經由高氧壓退火後，可回復其超導特性，量測到在溫度77 K時臨界電流IC = 80 μA，峰值電壓Vpp = 0.79 μV。經由所量測出的V-Φ曲線，可以看到我們所通的偏壓電流越大，其電壓調製幅度越大，當偏壓電流為100 μA時，電壓調製幅度達到極大值0.79 μV，隨後電壓調製幅度就會隨著所通的偏壓電流增加而減少，此與SQUID特性相符。

In this thesis, a sandwich-type technique for the fabrication of high-TC Superconducting Quantum Interference Devices(SQUIDs) is researched. We deposited YBa2Cu3O7-δ/CeO2/YBa2Cu3O7-δ trilayer thin films on SrTiO3 substrate by RF-magnetron sputtering technique and made the SQUIDs by using photolithography and ion-beam etching process. We measured the characteristic curves of the SQUIDs on this structure, and expected this technique could be a possible method to substitute the bi-crystal substrate SQUIDs. From the measured results, the roughness of the recycled substrates is 0.6 nm after polishing and annealing. The high-quality high-TC superconducting thin films were grown on the recycled substrates. We found that the SQUID characteristic has residual resistance at 77 K. However, after annealing at high oxygen pressure, it can recover its superconducting properties. Measured results show that critical current IC = 80 μA and peak-to-peak voltage Vpp = 0.79 μV with a bias current 100 μA at 77 K. The measured V-Φ curves show that, the larger the bias current, the larger amplitude of the voltage modulation, which agrees with the SQUID characteristic.