Interphase engineering in tantalum and aluminium superconducting resonators

The performance of cutting-edge superconducting quantum devices is primarily limited by microwave dielectric losses at various surface and interface regions. Potential enhancements in device performance may be achieved through the strategic modification of these interfaces, specifically through the incorporation of additional layers or the application of specific surface treatments. This will facilitate the understanding of the contributions of each interface to the overall device loss. In this study, we investigate the performance of alpha-tantalum and aluminum resonators, which have been fabricated utilizing various seed layers. We conduct an extensive characterization study of the device material using transmission electron microscopy, X-ray photoemission spectroscopy, X-ray diffraction, atomic force microscopy, and critical temperature measurements. Depending on the specific seed layer material employed, there is either a notable reduction in both low and high internal quality factors, or no discernible variation in comparison to the reference resonators.