Edge treatment for spurious mode suppression in thin-film lithium niobate resonators

Arjun Aryal; Sidhant Tiwari; Darren W Branch; Aleem Siddiqui; Tito Busani

doi:10.1038/s41598-024-71036-8

Edge treatment for spurious mode suppression in thin-film lithium niobate resonators

Sci Rep. 2024 Sep 9;14(1):21070. doi: 10.1038/s41598-024-71036-8.

Authors

Arjun Aryal^#^{1

2}, Sidhant Tiwari^#³, Darren W Branch³, Aleem Siddiqui⁴, Tito Busani^{5

6

7}

Affiliations

¹ Center for High Technology Materials (CHTM), University of New Mexico (UNM), MSC01 04-2710, 1313 Goddard SE, Albuquerque, NM, 87106-4343, USA.
² Optical Sciences and Engineering (OSE), University of New Mexico (UNM), MSC01 04-2710, 1313 Goddard SE, Albuquerque, NM, 87106-4343, USA.
³ Sandia National Laboratories (SNL), 1515 Eubank SE, Albuquerque, NM, 87123, USA.
⁴ Sandia National Laboratories (SNL), 1515 Eubank SE, Albuquerque, NM, 87123, USA. asiddiq@sandia.gov.
⁵ Center for High Technology Materials (CHTM), University of New Mexico (UNM), MSC01 04-2710, 1313 Goddard SE, Albuquerque, NM, 87106-4343, USA. busanit@unm.edu.
⁶ Optical Sciences and Engineering (OSE), University of New Mexico (UNM), MSC01 04-2710, 1313 Goddard SE, Albuquerque, NM, 87106-4343, USA. busanit@unm.edu.
⁷ Electrical and Computer Engineering (ECE), University of New Mexico (UNM), MSC01 11001, Albuquerque, NM, 87131-0001, USA. busanit@unm.edu.

^# Contributed equally.

Abstract

Thin-film lithium niobate is an attractive material for RF acoustic devices because of its high electromechanical coupling. However, due to the large coupling and the high anisotropy, thin-film lithium niobate resonators are prone to accidental resonances called spurious modes. These modes compromise the frequency response of the resonators, limiting their use in filter and oscillator applications. In this work, we present a novel method of spurious mode suppression through a special edge treatment etch process. Two thin-film lithium niobate resonators were fabricated, one with smooth sidewalls and one with the edge treatment. It was found that the edge-treated resonators show a weaker spurious mode response. This is potentially a new way to mitigate spurious resonances, a major issue in lithium niobate Lamb wave devices.

Keywords: Edge treatment; Electromechanical coupling; Etch process; Lamb wave devices; RF acoustic devices; Spurious modes suppression.