AVS 61st International Symposium & Exhibition
    MEMS and NEMS Wednesday Sessions
       Session MN-WeM

Paper MN-WeM11
Dynamic Range Effect on the Mass Sensitivity of Optomechanically Transduced NEMS Devices with a Poorer Q Value

Wednesday, November 12, 2014, 11:20 am, Room 301

Session: Optomechanics, Photonics, and Quantum Nanosystems
Presenter: S.K. Roy, University of Alberta and The National Institute for Nanotechnology, Canada
Authors: S.K. Roy, University of Alberta and The National Institute for Nanotechnology, Canada
V.T.K. Sauer, University of Alberta and The National Institute for Nanotechnology, Canada
W.K. Hiebert, University of Alberta and The National Institute for Nanotechnology, Canada
Correspondent: Click to Email
Suitable control over the oscillatory properties and tunable nonlinearities has made nanomechanical resonators attractive to the research community not only for their ultra-sensing ability but also for rich physics behind their optomechanical properties. Optomechanical transduction of these devices has become promising for optimizing device applications. The present work is aimed at studying the interplay between dynamic range (DR), mass sensitivity, and mechanical quality factor (Q), and measurement bandwidth in state-of-the-art optomechanical NEMS devices. While poorer Q is normally assumed to lead to degradation in mass sensing performance, there are situations where performance can be recovered, and even improved, through the dynamic range dependencies on Q. This is welcome news for applications at atmospheric pressure such as sensitive gas sensing. In quest of an appropriate mass or gas sensor, nonlinear oscillatory behaviour was studied on a doubly clamped beam of 8.75μmx220nmx160nm which is 160 nm away from a racetrack resonator optical cavity. To get the upper end of DR, the resonator was driven close to nonlinearity, i.e. to the amplitude where 1dB compression was observed. Thermomechanical noise signals were measured to achieve the bottom end of the DR. At high vacuum (<10-5 torr), 6 torr and 1atm the obtained experimental DR values are 53, 64 and 55 respectively. The corresponding Q values are 2866, 944 and 26. According to these experimental results, calculated mass sensitivity for the device were found 0.3, 0.2 and 28 Zepto g at high vacuum, 6 torr and 1atm respectively. An atmospheric pressure room temperature mass sensitivity of 28 zeptogram for Q value of 26 is an intriguing value. Such a surprising result of better mass sensitivity with poorer Q can be explained based on existing theories.