Epitaxial CeO2 Films as a Host for Quantum Applications

TL;DR

This study demonstrates that CeO2 films, with nuclei of zero nuclear magnetic moment, serve as promising hosts for quantum emitters, showing improved coherence times and insights into dopant-host interactions for quantum technology.

Contribution

The paper introduces epitaxial CeO2 films as a nuclear-spin-free host for quantum emitters, with detailed structural and electronic characterization, and compares dopant effects on luminescence lifetimes.

Findings

Er-doped CeO2 exhibits longer photoluminescence lifetimes than Tm-doped films.

High-quality CeO2 films can be grown with atomic smoothness and proper dopant incorporation.

Electronic structure analysis explains differences in non-radiative pathways between dopants.

Abstract

In highly purified host, the coherence of quantum emitters is ultimately limited by hyperfine interactions between the emitter and lattice nuclei possessing non-zero nuclear magnetic moments. This limitation can only be mitigated through isotopic purification. In this work, we investigate CeO2 as a host composed entirely of nuclei with zero nuclear moment. High-quality CeO2 thin films were grown by PLD and doped with Tm and Er ions. Structural characterization using X-ray diffraction, atomic force microscopy, and ion channeling confirms single-crystalline, atomically smooth films with dopants substitutionally incorporated at Ce lattice sites. Photoluminescence lifetime measurements show significantly longer lifetimes for Er-doped CeO2 (2.9 - 5.3 ms) compared with Tm-doped films (14 - 68 {\mu}s). Moreover, the Er-doped PLD films exhibit longer lifetimes at ~1% dopant concentration than previously reported for MBE-grown films. Density functional theory calculations reveal a substantial overlap between unoccupied O 2p and Tm 4f states near the valence band maximum, whereas Er 4f states remain well isolated. This electronic interaction likely introduces non-radiative recombination pathways in Tm-doped CeO2, explaining the reduced lifetimes. These findings highlight the importance of selecting appropriate dopant-host combinations and optimized growth conditions to minimize non-radiative channels for quantum applications.