Speaker
Description
Silicon Nitride resonators, due to dissipation dilution and soft clamping, are promising platforms for quantum sensing - even at room temperature. The extremely high $Q \times f$ product allows several coherent oscillations, and by coupling with a cavity they can become fully quantum objects with low phonon occupancy. Given the extremely high aspect ratio used in modern mechanical resonators, surface physics has become one of the limiting factors. In this work, we increase $Q$ with hyperthermal annealing up to 1200$^\circ$C in ultra-high vacuum. With this method, we achieve a $Q \times f = 8 \cdot 10^{14}$ with a phononic crystal membrane, which is, to our knowledge, the highest value reported for this kind of structure to date. To understand the underlying mechanism of surface loss reduction with annealing, we employ techniques such as XPS, FTIR, and ellipsometry, and we propose OH termination as a possible source of mechanical damping.