Non-contact excitation of multi-GHz lithium niobate electromechanical resonators

TL;DR

This paper introduces a contactless excitation method for lithium niobate electromechanical resonators, significantly improving their quality factor by separating electrodes from the resonator using flip-chip bonding, thus reducing damping and spurious modes.

Contribution

The study presents a novel flip-chip bonding technique that enables non-contact excitation of lithium niobate resonators, reducing mass-loading effects and enhancing device performance.

Findings

Increased quality factor of resonators with non-contact excitation

Reduction of spurious modes and damping effects

Demonstrated feasibility of flip-chip bonding for high-frequency resonators

Abstract

The demand for high-performance electromechanical resonators is ever-growing across diverse applications, ranging from sensing and time-keeping to advanced communication devices. Among the electromechanical materials being explored, thin-film lithium niobate stands out for its strong piezoelectric properties and low acoustic loss. However, in nearly all existing lithium niobate electromechanical devices, the configuration is such that the electrodes are in direct contact with the mechanical resonator. This configuration introduces an undesirable mass-loading effect, giving rise to spurious modes and additional damping. Here, we present an electromechanical platform that mitigates this challenge by leveraging a flip-chip bonding technique to separate the electrodes from the mechanical resonator. By offloading the electrodes from the resonator, our approach yields a substantial increase in the quality factor of these resonators, paving the way for enhanced performance and reliability for their device applications.