Determination of thin film properties using SAW delay lines

The aim of this project is to use numerical simulations to reproduce and match the material properties of thin films, with particular attention to their temperature coefficients. The overall strategy is to build on existing literature addressing acoustic characterization of layered piezoelectric structures and to adapt the underlying methodology to our specific materials and simulation data. The focus is strictly on the simulation domain, where acoustic-wave behavior can be controlled, isolated, and systematically analyzed. Acoustic waves propagate within solids at velocities determined by intrinsic material parameters such as stiffness, density, and piezoelectric constants. By modifying these parameters in a controlled simulation environment, together with geometric factors such as film thickness, oxide layers, and transducer layout, one can quantify their influence on wave dispersion and, by extension, on the effective temperature coefficients of frequency (TCF). In this report, we first present the theoretical and numerical framework used to model surface acoustic waves in thin-film lithium niobate structures. We then analyze the behavior of a single resonator to identify and track the antisymmetric A1 Lamb mode, which serves as the primary mode of interest for delay-line operation. The methodology is subsequently extended to differential delay lines, enabling robust extraction of phase and group velocities through differential-phase analysis and time-domain validation. A key part of the report examines how SiO2 layers of varying thickness and material properties (Young’s modulus and density) alter the acoustic response, mode purity, and extractability of velocity information. Finally, the limitations of the method, the stability of the extraction across configurations, and the feasibility of using these simulations for temperature-dependent material-property estimation are discussed.