Surface modification and coherence in lithium niobate SAW resonators

Creators: Gruenke, Rachel G.; Hitchcock, Oliver A.; Wollack, E. Alex; Sarabalis, Christopher J.; Jankowski, Marc; McKenna, Timothy P.; Lee, Nathan R.; Safavi-Naeini, Amir H.

Abstract

Lithium niobate is a promising material for developing quantum acoustic technologies due to its strong piezoelectric effect and availability in the form of crystalline thin films of high quality. However, at radio frequencies and cryogenic temperatures, these resonators are limited by the presence of decoherence and dephasing due to two-level systems. To mitigate these losses and increase device performance, a more detailed picture of the microscopic nature of these loss channels is needed. In this study, we fabricate several lithium niobate acoustic wave resonators and apply different processing steps that modify their surfaces. These treatments include argon ion sputtering, annealing, and acid cleans. We characterize the effects of these treatments using three surface-sensitive measurements: cryogenic microwave spectroscopy measuring density and coupling of TLS to mechanics, X-ray photoelectron spectroscopy and atomic force microscopy. We learn from these studies that, surprisingly, increases of TLS density may accompany apparent improvements in the surface quality as probed by the latter two approaches. Our work outlines the importance that surfaces and fabrication techniques play in altering acoustic resonator coherence, and suggests gaps in our understanding as well as approaches to address them.

Copyright and License

© The Author(s) 2024. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Acknowledgement

The authors would like to thank Dr. Agnetta Cleland, Dr. Juliet Jamtgaard, Takuma Makihara, Kevin K. S. Multani, Dr. Carsten Langrock, and Professor Martin Fejer for experimental support and helpful discussions. We acknowledge funding from Amazon Web Services Inc., the David and Lucile Packard Fellowship and the Stanford University Terman Fellowship, as well as the U.S. government through the National Science Foundation CAREER award No. ECCS-1941826, the Office of Naval Research (ONR) under grant No. N00014-20-1-2422, the U.S. Air Force Office of Scientific Research (MURI Grant No. FA9550- 17-1-0002), and the U.S. Department of Energy through Grant No. DE-AC02-76SF00515 (through SLAC). E.A.W. was supported by the Department of Defense through the National Defense & Engineering Graduate Fellowship. Part of this work was performed at the Stanford Nano Shared Facilities (SNSF) and at the Stanford Nanofabrication Facility (SNF), supported by the National Science Foundation under award ECCS-2026822. The authors wish to thank NTT Research for their financial and technical support.

Contributions

R.G.G. designed and fabricated all devices tested, performed all TLS, XPS and AFM measurements, and analysed the data. O.A.H. and C.J.S. aided in design of the devices, and O.A.H and R.G.G. developed the fabrication process. E.A.W. and N.R.L. provided experimental and theoretical support for the cryogenic measurements. M.J. and T.P.M. aided in the AFM measurements. R.G.G. and A.H.S.N. wrote the manuscript. A.H.S.N. supervised all efforts.

Data Availability

The data supporting the conclusions of this study are available from the corresponding author upon reasonable request.

Supplementary Information

Conflict of Interest

E. Alex Wollack is currently a research scientist at Amazon, and A. H. Safavi-Naeini is an Amazon Scholar. The other authors declare no competing financial interests.

Files

s41598-024-57168-x.pdf

Files (5.4 MB)

Name	Size	Download all
s41598-024-57168-x.pdf md5:ab1da7b6853eb27c9296ef173c2d46e9	2.0 MB	Preview Download
41598_2024_57168_MOESM1_ESM.pdf md5:b5e80594f41ae52ca5693780d24d9cc8	3.4 MB	Preview Download

	All versions	This version
Views	0	0
Downloads	0	0
Data volume	0 Bytes	0 Bytes