Acoustic microscopy study on elasto-mechanical properties of Lu3Al5O12:Ce single crystalline films

This article presents experimental, theoretical, and numerical studies of the propagation of guided ultrasonic waves in a layered epitaxial structure of garnet compounds. A microscopic model, yielding dispersion equations based on material and geometrical properties, was developed. Acoustic microscopy experiments both on YAG:Ce crystal substrate and epitaxial structure containing LuAG:Ce single crystalline films grown using the Liquid Phase Epitaxy growth method onto YAG:Ce crystal substrate revealed distinct phase velocity behaviors. The YAG substrate exhibited consistent velocities, minimally influenced by frequency, while the epitaxial structure showed dispersion, indicating frequency-dependent phase velocities. Experimental results were compared with numerically calculated dispersion curves, showing high agreement in the low-frequency range and minor deviations at higher frequencies. An optimization procedure was developed and applied, starting with the YAG substrate and extending to the LuAG:Ce film/YAG:Ce crystal epitaxial structure. The procedure allowed us to extract material properties, offering valuable insights into the mechanical characteristics of the all-solid-state LuAG:Ce film/YAG:Ce crystal structure. This research represents a significant advancement in understanding ultrasonic wave dynamics in layered structures, particularly unveiling previously unexplored elastic properties of LuAG:Ce single crystalline films as well-known scintillation material.