Superiority of high power impulse magnetron sputtering in niobium films deposition on copper

With the development of radio frequency superconducting accelerator, research on thin film coated copper cavity becomes increasingly attentive.High Power Impulse Magnetron Sputtering (HiPIMS) is a kind of promising emerging PVD technique in comparision with dc magnetron sputtering already used on thin film coated copper cavities.In this paper, the physical properties of niobium films condensed by conventional dc magnetron sputtering (DCMS) and by high power impluse magnetron sputtering (HiPIMS) are evaluated and compared.The dc superconductivity of films with these two techniques is similar and all transition temperature is 9.5K.Further more, the microstructure of niobium films deposited by HiPIMS at 150 °C belong to zone T in contrast to that by DCMS in zone I. From AFM results, the surface roughness by HiPIMS and DCMS is 3.92±0.14nm and 6.67±0.39nmindividually.Adhesion strength is obtained by scratch tests and the films critical load L C by HiPIMS is 5.53±0.93Nand that by DCMS is 1.99±0.13N.Films by HiPIMS have better structure-properties including morphology, surface roughness, and adhesion strength, which are beneficial to Q-slope mitigation in niobium film coated copper superconducting cavities.