# First-Principles Calculations and PMUT Applications of Piezoelectric Thin-Film Materials

## TL;DR

This paper introduces a new method combining atomic-level calculations and simulations to improve the design of ultrasonic transducers for better medical imaging and sensing.

## Contribution

A novel optimization framework integrating first-principles calculations with multiphysics simulations to enhance PMUT design accuracy and efficiency.

## Key findings

- PZT has higher electromechanical coupling coefficient than ScAlN, making it better for actuation.
- An analytical acoustic-field model reduces computational cost while maintaining accuracy compared to full-wave simulations.
- Hexagonal PMUT elements outperform circular ones with higher acoustic output and frequency.

## Abstract

High-performance piezoelectric micromachined ultrasonic transducers (PMUTs) are crucial for portable medical imaging and sensing. The efficiency of advanced PMUTs relies on high-quality piezoelectric thin films and optimized device designs. However, variability in common piezoelectric thin films like ScxAl1−xN (ScAlN) and PbZr1−xTixO3 (PZT) often leads to inaccurate material parameters—especially those derived from thick ceramics. To enhance simulation accuracy in standard designs affected by these inconsistencies, this work introduces an optimization framework combining first-principles calculations with multiphysics simulations. First, the intrinsic properties of PZT and ScAlN are analyzed through atomistic calculations, confirming that PZT, with its higher electromechanical coupling coefficient, is better suited for actuation. The parameters obtained from these calculations calibrate the finite-element model, addressing issues of missing or inaccurate data in commercial software libraries. Next, an efficient analytical acoustic-field model is developed. Compared to full-wave simulations in COMSOL, this model significantly reduces computational cost while maintaining accuracy, allowing for quicker scanning and optimization of large-array topologies. Additionally, results demonstrate that each individual hexagonal PMUT element outperforms a comparable circular element, achieving a peak SPL of 90.4 dB at 4.9 MHz versus 89.7 dB at 2.8 MHz. This higher acoustic output and operating frequency enable improved spatial resolution and sensitivity. This modeling approach, based on intrinsic material properties, provides a solid theoretical foundation for designing high-precision, low-power ultrasonic devices.