Improving the Luminescent Properties of Atomic Layer Deposition Eu:Y₂O₃ Thin Films through Optimized Thermal Annealing

Crystalline rare‐earth (RE)‐doped Y 2 O 3 films are an attractive system for a wide range of photonics applications including quantum technologies which aim at harnessing optical or spin transitions with long coherence times to achieve new functionalities such as quantum storage or information processing. Herein, atomic layer deposition (ALD) of Eu‐doped Y 2 O 3 thin films with improved optical properties is presented. A crucial post‐treatment step to obtain high‐quality films is annealing at elevated temperatures (>900 °C). However, the main drawback of this approach is the formation of unwanted parasitic phases due to reaction at the interface with the substrate, especially with silicon. In this article, this issue is discussed for different kinds of substrates and buffer layers. The use of such modified substrates allows advantageously extending the maximum thermal treatment up to 1150 °C without being limited by interface reactions. It is demonstrated that the emission of the 5 D 0 → 7 F 2 transition for Eu 3+ in Y 2 O 3 film can be as narrow as that of bulk materials when optimized thermal treatments and a thin undoped Y 2 O 3 buffer layer are used. Thus, a versatile method to reduce the impact of the substrate–film interface on the optical properties is proposed.