[21p-232-1~18] 6.2 Carbon-based thin films

▲ [21p-232-17] Ultrahigh quality factors single crystal diamond MEMS resonators

〇Meiyong Liao¹, Haihua Wu¹, Liwen Sang¹, Masataka Imura¹, Tokuyuki Teraji¹, Yasuo Koide¹ (1.NIMS)

Keywords:MEMS, diamond

In this work, we aim to achieve ultrahigh quality factor SCD resonators by removing the defective layer formed at the bottom of the SCD resonators during the fabrication process. Our approach is to etch the defective layer by using oxygen gas at 500^oC. The cantilevers contain intrinsic epilayers grown by microwave plasma chemical vapour deposition (MPCVD) on the ion-implantation damaged diamond layers. The HPHT SCD was utilized as the substrate. The length of the SCD cantilevers ranges from 30-150 µm, the width is from 6-12 µm, and the thickness is ~1.6 µm. The SCD cantilevers were thermal treated in an oxygen ambient with different time durations up to 380 hrs at 500^oC. The mechanical resonance of the SCD cantilevers was measured by a laser Doppler technique. We confirmed that the resonance frequency well followed the inverse power law relationship with the length of the cantilevers, giving an estimated Young’s modus around 1100GPa. It was observed that the Q-factors were significantly improved from around 1000 to more than 500 000. A shift of the resonance frequency was also observed, supporting the etching effect by oxygen. The improvement in the Q-factor is attributed to the removal of the damaged diamond layer.