AVS 53rd International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP19
The Effect of Chemical Bonding on Energy Dissipation in Functionalized Silicon Resonators

Tuesday, November 14, 2006, 6:00 pm, Room 3rd Floor Lobby

Session: Surface Science Poster Session
Presenter: A.M. Richter, Cornell University
Authors: A.M. Richter, Cornell University
D. Sengupta, Cornell University
M.A. Hines, Cornell University
Correspondent: Click to Email
Low cost chemical or biological sensors could potentially be fabricated from micromechanical resonators, such as simple cantilevers; however, the realization of this goal has been impeded by the low performance and stability of current micromechanical devices. The sensitivity of a resonant detector is determined, in part, by its rate of mechanical energy dissipation. High mechanical energy dissipation (i.e. low quality factor, Q) leads to poor sensitivity. In previous research, we have shown that the rate of mechanical energy dissipation in MHz-range silicon resonators is profoundly affected by the chemical state of the surface. By changing a single monolayer of molecules on the surface of a 5-µm-wide, 250-nm-thick silicon resonator - less than 0.07% of the total mass - the quality factor of the resonator can be improved at least 70%. In this study, we probe the chemical origins of this effect by comparing the performance of two different types of alkyl-terminated resonators. In the first type, the alkyl chain is directly bonded to the silicon surface through a Si-C bond, whereas in the second type, the alkyl chain is bonded through a Si-O-C linkage. These monolayers were formed by the direct reaction of primary alkenes (Si-C linkage) or primary alcohols or aldehydes (Si-O-C linkage) with H-terminated silicon surfaces. The monolayers were characterized using surface infrared spectroscopy, then their affect on resonator performance was characterized using interferometric detection. Both the chemical linkage (Si-C vs. Si-O-C) and the monolayer precursor (alcohol vs. aldehyde) significantly affected performance. The chemical basis of these differences will be discussed.