Structural and Optical Characterization of Erbium-doped Anatase TiO₂ Thin Films on LaAlO₃ (001)

Rare-earth ion (REI) dopants in solid-state host crystals are gaining interest as an attractive platform for quantum information processing due to long coherence times and potential scalability. Recent efforts to improve coherence times in REI dopants have focused on finding suitable host crystals with minimal sources of decoherence (e.g., nuclear spin, oxygen vacancies, and strain variation). Molecular beam epitaxy (MBE) offers advantages in this regard, as it can grow epitaxial films using highly pure elemental sources and isotopically purified materials. In addition, MBE growth can provide these materials in thin film and heterostructure forms that offer flexible and scalable host crystal environments.<br/><br/>Here, we report on the MBE growth of Er-doped anatase TiO₂ thin films on LaAlO₃ (001) substrates with varying doping concentrations. We characterize them using x-ray diffraction and photoluminescence (PL) measurements to investigate how factors such as the Er concentration, buffer layer and delta-doping affect the optical inhomogeneous linewidths of Er³⁺ ions. Initial results show Er³⁺ PL from two different sites in TiO₂ and one site in LaAlO₃, with PL intensities consistent with the doping concentration.<br/><br/>*This work is supported by the U.S. Department of Energy, Office of Science, National Quantum Information Science Research Centers, Co-design Center for Quantum Advantage (C2QA) under contract number DE-SC0012704.