Effect of thermal annealing on the structural evolution of thin ceramic YAG: Ce films grown by pulsed laser deposition

Abstract

It is well established that the performance of LED and laser devices can be enhanced by optimizing the heat sink. Aluminum oxide (Al₂O₃) is one of the most effective materials for use as a heat sink. In this study, YAG: Ce³⁺ thin films were deposited onto sapphire substrates with a (0001) orientation using pulsed laser deposition method. It was observed that the annealing temperature did not significantly affect the thickness of the films, but it did influence their uniformity and structure. As the annealing temperature of the YAG: Ce films increased, crystallite growth was noted. The polydispersity of the grains also increased with higher annealing temperatures, indicating competitive growth phenomena. Raising the annealing temperature to 1400 °C led to the formation of gaps in the film structure due to recrystallization processes. Luminescence measurements revealed that, despite the structural differences among films annealed at various temperatures, their emission spectra remained consistent with the target. This suggests the stability of the energy structure of YAG: Ce and the successful transfer of YAG stoichiometry during the pulsed laser deposition process. As a result, optimal conditions for the thermal annealing of YAG: Ce thin films were identified, leading to high crystalline perfection and the formation of a heteroepitaxial interface with the Al₂O₃ (0001) substrate. This finding is potentially significant for enhancing the thermal characteristics of composite structures.