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

Rare-earth ion (REI) defects in solid-state hosts are an attractive platform for quantum information processing due to long coherence times and potential scalability. Recent efforts to increase coherence times in REI defects have focused on finding suitable host crystals with minimal sources of decoherence (e.g., nuclear spin, oxygen vacancies, and strain variation). To this end, molecular beam epitaxy (MBE) offers advantages, 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.

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.