| AVS 64th International Symposium & Exhibition | |
| MEMS and NEMS Group | Wednesday Sessions |
| Session MN+2D-WeM |
| Session: | 2D NEMS |
| Presenter: | Hailong Chen, Case Western Reserve University |
| Authors: | H. Chen, Case Western Reserve University V. Pashaei, Case Western Reserve University W. Liao, Vanderbilt University C.N. Arutt, Vanderbilt University H. Jia, Case Western Reserve University M.W. McCurdy, Vanderbilt University C.A. Zorman, Case Western Reserve University R.A. Reed, Vanderbilt University R.D. Schrimpf, Vanderbilt University M.L. Alles, Vanderbilt University P.X.-L. Feng, Case Western Reserve University |
| Correspondent: | Click to Email |
Radiations effects from energetic particles (ions) and electromagnetic waves (photons) on electronics (e.g., MOSFETs and ICs) have been widely investigated for applications in radiative harsh environments including space and nuclear reactors [1]. Radiation effects in mechanical domain, however, remain largely unexplored due to challenges in capturing and detection [2]. Meanwhile, most of preliminary studies on radiation effects in mechanical domain have been limited to Si structures and devices [3-4], while those on more intriguing radiation-durable materials such as SiC have not been investigated yet.
Here we report on experimental investigation and analysis of energetic ion radiation effects on silicon carbide (SiC) crystal, by exploiting a novel scheme of 4 vertically stacked resonant micromechanical SiC diaphragms. The SiC diaphragms are fabricated using a standard photolithographic and wet etching process to form resulting diaphragms (1 mm × 1 mm × 2.1 µm). An S-series Pelletron system is employed to irradiation oxygen ions into the SiC diaphragms (14.3MeV, 8h radiation, corresponding to a total fluence of 5.6 ×1013/cm2). Before and after radiation, multimode resonances are characterized in vacuum by using an ultrasensitive optical interferometry system. We have observed as large as ~9% frequency shifts (the largest value to date) in the multimode resonances of the 3rd diaphragm (counting from top in the stack) where most ions are expected to stop, as well as obvious quality (Q) factor degradation, which result from ionizing and displacement radiation damage. The 1st and 2nd diaphragms, which ions have mostly penetrated, exhibit moderate multimode frequency downshift of ~2% owing to displacement damage, while the 4th diaphragm shows the least frequency shift ~0.1%. The diaphragm stack exhibits outstanding capability for probing radiation damages in MEMS, not only able to capture the radiation events obviously but also help analyze different amount and types of damages induced in each stacking layer. Combining the data with a mixed elasticity model (that takes into account both flexural rigidity and pre-tension effects), we find: (i) the diaphragms operate in the transition regime (between ‘plate’ and ‘membrane’ but closer to the latter). (ii) after radiation behavior moves further towards the ‘plate’ regime, suggesting reduction in built-in tension and possible reduction in Young’s modulus as well.
[1] J.R. Schwank, et al., IEEE Trans. Nucl. Sci. 55, 2008.
[2] H. Shea, et al., J. Micro/Nanolith. MEMS MOEMS. 8, 2009.
[3] B. Bhandaru, et al., IEEE Trans. Nucl. Sci. 62, 2015.
[4] H. Gong, et al., IEEE Trans. Nucl. Sci. 64, 2017.