# Fileset

[IEEE NEMS 2024_Abstract_V4 _Chen Guo.docx](https://mdr.nims.go.jp/filesets/1c330a81-3ba9-492c-8170-f5c6a0c92975/download)

## Creator

Guo Chen, Zilong Zhang, Keyun Gu, Liwen Sang, [Satoshi Koizumi](https://orcid.org/0000-0003-4961-5658), Masaya Toda, [Yasuo Koide](https://orcid.org/0000-0001-8321-9822), Zhaohui Huang, [Meiyong Liao](https://orcid.org/0000-0003-1361-4266)

## Rights

[In Copyright](http://rightsstatements.org/vocab/InC/1.0/)

## Other metadata

[High-order resonance of single-crystal diamond MEMS with high-quality factor at high temperatures](https://mdr.nims.go.jp/datasets/6b6b9788-6f2f-4bd5-8d40-2fbccacff734)

## Fulltext

HIGH-ORDER RESONANCE OF SINGLE-CRYSTAL DIAMOND MEMS WITH HIGH-QUALITY FACTOR AT HIGH TEMPERATURESGuo Chen1,2, Zilong Zhang1, Keyun Gu1, Liwen Sang1, Satoshi Koizumi1, Masaya Toda3, Yasuo Koide1, Zhaohui Huang2, Meiyong Liao1*Novelty / Progress Claim(s)MEMS resonators are typically engineered to function at their first vibration mode, and extensive research has been dedicated to understanding and optimizing this fundamental mode. However, despite the demonstrated effectiveness of operating at high modes for achieving high sensitivity in MEMS sensing applications, there is currently no reported research on higher-order modes at high temperatures. This paper reports an investigation on the resonance properties of higher-order vibration modes of single-crystal diamond (SCD) MEMS, specifically focusing on their performance at elevated temperatures up to 500°C. It is shown that the second mode of SCD cantilever exhibits a high-quality factor of 9,541 and high thermal stability of less than 10 ppm/°C at 500°C.Background / State of the ArtSingle-crystal diamond (SCD) is emerging as an ideal semiconductor material for MEMS resonant sensors in challenging environments contributed to its exceptional properties, i.e., the highest mechanical properties, such as the highest Young's modulus, extreme hardness, and thermal stability of resonance frequency [1-3]. In our previous work, we successfully accomplished the mass production of SCD MEMS resonators by a smart-cut method [4]. Additionally, we achieved diamond MEMS resonators magnetic sensing up to 500°C by operating the first mode [5]. Nevertheless, higher-order resonance modes have been demonstrated to achieve high performance in MEMS resonators [6]. Therefore, it is of great importance to examine the higher-order modes of MEMS resonators at high temperatures. In this work, we aim to investigate the performance of higher-order modes of SCD MEMS cantilevers in high temperature environments. We measured the resonance frequency and quality (Q) factors of diamond cantilevers in a higher-order vibration mode at high temperatures up to 500°C. Description of the New Method or System In this study, we fabricated SCD MEMS cantilevers with high Q factors by utilizing the smart-cut method. We report for the first time the high-order vibration mode in SCD MEMS cantilevers at high temperatures up to 500°C, using an in-situ measurement equipment. We investigated the resonance performance and thermal stability of the diamond cantilevers under the second mode in high-temperature environment. The temperature dependence of the resonance frequency and Q factor variations for the SCD cantilevers in high-order mode were analyzed.Experimental ResultsThe optical image of the SCD cantilevers is depicted in Figure 1, which was on a SCD substrate with an epitaxial diamond layer. These MEMS cantilevers were fabricated by the smart-cut method, possessing dimensions of 140 µm in length (L), 880 nm in thickness (t), and 10 µm in width (w). In Figure 2, the resonance frequency spectra of the diamond cantilever operating in the first two vibration modes at 500°C is presented. The resonance frequency of the high-order is measured at 2.073 MHz, with a high Q factor of 9,541 calculated by Lorentz fitting. Figure 3 shows the resonant frequency shift of the cantilever in the 2nd order vibration across the temperature range from 25 to 500°C. It can be seen that the resonance frequency decreases with increasing temperature. As illustrated in Figure 4, the temperature coefficient of resonance frequency (TCF) for the diamond MEMS cantilever remains below 10 ppm/°C up to 500°C. This performance surpasses that of silicon, which has a TCF value of 35 ppm/°C [7]. The lower TCF value in diamond indicates superior thermal stability of the second-order mode, similar as that of the fundamental mode. Figure 5 exhibits the temperature dependence of the Q factors in the first two orders. It is evident that the Q factors of the diamond cantilever in both modes decreased at high temperatures. However, the higher temperature, the less difference of Q factors between the first order and the second order. As a result, the high-order mode of the diamond cantilever exhibits low TCF and high Q factor at high temperatures, ensuring high reliability and sensitivity for MEMS resonant sensors, especially in extreme environments.1 National Institute for Materials Science, Japan, 2 China University of Geosciences (Beijing), China,3 Tohoku University, JapanCorrespondence: Meiyong Liao, e-mail: meiyong.liao@nims.go.jpThis work was supported by JSPS KAKENHI (Grant Number 20H02212, 22K18957), Bilateral joint research between JSPS/CAS, ARIM of MEXT (JPMXP1223NM5297). Guo Chen thanked to financial support from China Scholarship Council (No. 202006400023).Figure 5: Dependence of Q factors at high temperatures in the first two vibration modes of diamond MEMS cantilevers.References[1] M. Liao, Functional Diamond, 1 (2022), pp. 29-46.[2] G. Chen, et.al, Proc. TRANSDUCERS 2023, pp. 2185-2188.[3] G. Chen, et.al, Diam. Relat. Mater, 138 (2023), 110240.[4] M. Liao, et.al, Adv. Mat, 22 (2010), 5393.[5] Z. Zhang, et.al, Proc. TRANSDUCERS 2023, pp. 2082-2085.[6] W. Zhao, et al. Mech. Syst. Signal Process, 196 (2023), 110347.[7] M. Toda, et.al, IEEJ Trans, 12 (2017), pp. 153-160. Figure 4: Temperature coefficient of resonance frequency (TCF) of the diamond MEMS cantilevers in the first two orders.Figure 3: Dependence of resonance frequency at high temperatures in the 2nd order vibration mode of diamond MEMS cantilevers.Figure 2: The resonance frequency spectrum of a 140 µm-length SCD cantilever in the first two orders at 500℃.Figure 1: Optical image of typical diamond MEMS cantilevers with length of 140 µm, fabricated by IAL method.image20.tifimage3.tifimage30.tifimage4.tifimage40.tifimage5.tifimage50.tifimage1.tifimage10.tifimage2.tif