Broad excitation of Er luminescence in Er-doped HfO2 films

We investigated the broad and sensitized luminescence properties of Er-doped HfO₂ films synthesized by pulsed laser deposition (PLD) and ion implantation techniques. In the investigation we focused on the mechanism of energy transfer in the host matrix. Based on the comparison of photoluminescence (PL), photoluminescence excitation (PLE), and cathode-luminescence (CL), as well as on microstructure measurements, an excitation transfer process resulting in the broad excitation for Er, luminescence at 1540 nm, is identified. In this process, the oxygen vacancies and Hf in the host HfO₂ serve mainly as effective sensitizers for neighboring Er ions in the nonresonant excitation process. Furthermore, the direct Er³⁺ intra-4f transitions and full spectral emission of Er ions in the HfO₂ matrix are clearly observed under the wide-spectrum excitation in the CL measurement. This reveals more detailed features for the energy transfer and transition processes.