This work explores erbium-doped calcium molybdate (CaMoO4) thin films grown on silicon and yttria stabilized zirconia (YSZ) substrates, as a potential solid state system for C-band (utilizing the ∼1.5 μm Er3+ 4f-4f transition) quantum emitters for quantum network applications. Through molecular beam epitaxial growth experiments and electron microscopy, X-ray diffraction and reflection electron diffraction studies, we identify an incorporation limited deposition regime that enables a 1:1 Ca:Mo ratio in the growing film leading to single phase CaMoO4 formation that can be in-situ doped with Er (typically 2-100 ppm). We further show that growth on silicon substrates is single phase but polycrystalline in morphology; while growth on YSZ substrates leads to high-quality epitaxial single crystalline CaMoO4 films. We perform preliminary optical and microwave characterization on the suspected Y1−Z1 transition of 2 ppm, 200 nm epitaxial CaMoO4 annealed thin films and extract an optical inhomogeneous linewidth of 9.1(1) GHz, an optical excited state lifetime of 6.7(2) ms, a spectral diffusion-limited homogeneous linewidth of 6.7(4) MHz, and an EPR linewidth of 1.10(2) GHz.
@article{arxiv.2508.15122,
title = {Microstructural and preliminary optical and microwave characterization of erbium doped CaMoO$_4$ thin films},
author = {Ignas Masiulionis and Bonnie Y. X. Lin and Sagar Kumar Seth and Gregory D. Grant and Wanda L. Lindquist and Sungjoon Kim and Junghwa Kim and Angel Yanguas-Gil and Jeffrey W. Elam and Jiefei Zhang and James M. LeBeau and David D. Awschalom and Supratik Guha},
journal= {arXiv preprint arXiv:2508.15122},
year = {2025}
}