Kavli Nanoscience Institute and Condensed Matter Physics, California Institute of Technology, Pasadena, California 91125, United States.
Nano Lett. 2013 Apr 10;13(4):1528-34. doi: 10.1021/nl304687p. Epub 2013 Mar 7.
We investigate use of nanomechanical torsional resonators for frequency-shift-based infrared (IR) thermal sensing. Nanoscale torsion rods, ~1 μm long and 50-100 nm in diameter, provide both extraordinary thermal isolation and excellent angular displacement and torque sensitivities, of order ~10(-7) rad·Hz(-1/2) and ~10(-22) (N·m) Hz(-1/2), respectively. Furthermore, these nanorods act as linear torsional springs, yielding a maximum angular displacement of 3.6° and a dynamic range of over 100 dB; this exceeds the performance of flexural modes by as much as 5 orders of magnitude. These attributes lead to superior noise performance for torsional-mode sensing. We demonstrate the operational principles of torsional-mode IR detection, attaining an uncooled noise equivalent temperature difference (NETD) of 390 mK. By modeling the fundamental noise processes, we project that further reduction of device size can significantly improve thermal responsivity; a room-temperature NETD below 10 mK appears feasible.
我们研究了基于纳米机械扭转谐振器的频率移动红外（IR）热传感技术。纳米级扭转杆，长度约为 1 微米，直径为 50-100nm，具有极好的热隔离性能和出色的角位移和扭矩灵敏度，分别约为 10(-7) rad·Hz(-1/2)和 10(-22) (N·m) Hz(-1/2)。此外，这些纳米棒充当线性扭转弹簧，产生最大角位移为 3.6°，动态范围超过 100dB；这比弯曲模式的性能高出多达 5 个数量级。这些特性为扭转模式传感带来了卓越的噪声性能。我们展示了扭转模式 IR 检测的工作原理，实现了未冷却噪声等效温差（NETD）为 390mK。通过对基本噪声过程进行建模，我们预计进一步减小器件尺寸可以显著提高热响应率；在室温下，NETD 低于 10mK 似乎是可行的。
