Microstructural and optical characterization of Erbium-doped calcium tungstate films on yttria-stabilized zirconia

Er3+-doped bulk CaWO4 has been demonstrated to be a promising platform for quantum repeaters. However, the use of bulk crystals presents challenges for device integration and scalability. In this paper, we address the scalability of this platform by realizing thin-film CaWO4 growth on yttria-stabilized zirconia wafers, a step toward a CMOS-compatible heterogeneous platform. The films were deposited via radio-frequency magnetron sputtering, a scalable method, followed by postdeposition annealing and were in situ doped with Er. Optical characterization of the Er3+ ions in these films reveals lifetimes of 2.28 ± 0.16 ms, inhomogeneous linewidths of 48.29 ± 0.96 GHz, and a spectral-diffusion-limited homogeneous linewidth of 12.61 ± 2.79 MHz. These results are comparable to previously reported Er3+ in rare-earth oxide thin film hosts. The results highlight the potential of sputtered Er3+-doped CaWO4 thin films for quantum coherent applications.