超高真空磁控溅射生长铌薄膜

Deposition of Niobium Films by Ultra-High-Vacuum Magnetron Sputtering

金属铌的超导转变温度高,在超导电子学和超导量子电路中有着广泛的应用。铌膜通常采用常规磁控溅射设备进行制备。为了改善铌膜的质量,利用超高背景真空的磁控溅射设备进行铌膜制备工艺的研究非常重要。结合真空分析表征、低温输运测量等技术系统性地研究了溅射参数对铌膜表面粗糙度和晶粒大小的调控,并分析了生长条件对铌膜超导转变温度和剩余电阻比的影响。利用硅上铌膜制备的共面波导谐振器,在10 mK温度,单光子激励下,本征品质因子超过一百万,表明超高真空磁控溅射生长的铌膜微波损耗极低。

Due to its high superconducting transition temperature,niobium(Nb)is widely in superconducting electronics and quantum circuits. Nb films are usually deposited by conventional magnetron sputtering tools. To improve the film quality,it is important to use magnetron sputtering with ultra-high vacuum(UHV)background.Here the effects of UHV sputtering parameters on the surface roughness,grain size,transition temperature,and residual resistance ratio of the niobium films have been studied. Coplanar waveguide resonators made from a Nb film on silicon show intrinsic quality factor of one million at single-photon excitation under millikelvin temperature. It suggests that the Nb film deposited by UHV sputtering is of high quality and ultra-low microwave loss.