Ambacher, Oliver

Brückner, Klemens

Cengher, Dorin

Cimalla, Volker

Haupt, Christian

Hein, Matthias

Stephan, Ralf

Tonisch, Katja

Will, Florentina

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  PROCEEDINGS 11-15 September 2006      FACULTY OF ELECTRICAL ENGINEERING AND INFORMATION SCIENCE    INFORMATION TECHNOLOGY AND ELECTRICAL ENGINEERING - DEVICES AND SYSTEMS, MATERIALS AND TECHNOLOGIES FOR THE FUTURE      Startseite / Index: http://www.db-thueringen.de/servlets/DocumentServlet?id=12391 51. IWK Internationales Wissenschaftliches Kolloquium International Scientific Colloquium Impressum  Herausgeber: Der Rektor der Technischen Universität llmenau  Univ.-Prof. Dr. rer. nat. habil. Peter Scharff  Redaktion: Referat Marketing und Studentische Angelegenheiten  Andrea Schneider   Fakultät für Elektrotechnik und Informationstechnik  Susanne Jakob  Dipl.-Ing. Helge Drumm  Redaktionsschluss: 07. Juli 2006  Technische Realisierung (CD-Rom-Ausgabe):  Institut für Medientechnik an der TU Ilmenau  Dipl.-Ing. Christian Weigel  Dipl.-Ing. Marco Albrecht  Dipl.-Ing. Helge Drumm  Technische Realisierung (Online-Ausgabe):  Universitätsbibliothek Ilmenau    Postfach 10 05 65  98684 Ilmenau  Verlag:   Verlag ISLE, Betriebsstätte des ISLE e.V.  Werner-von-Siemens-Str. 16  98693 llrnenau   © Technische Universität llmenau (Thür.) 2006  Diese Publikationen und alle in ihr enthaltenen Beiträge und Abbildungen sind urheberrechtlich geschützt. Mit Ausnahme der gesetzlich zugelassenen Fälle ist eine Verwertung ohne Einwilligung der Redaktion strafbar.   ISBN (Druckausgabe): 3-938843-15-2 ISBN (CD-Rom-Ausgabe): 3-938843-16-0  Startseite / Index: http://www.db-thueringen.de/servlets/DocumentServlet?id=12391  51st Internationales Wissenschaftliches Kolloquium Technische Universität Ilmenau  September 11 – 15, 2006  F. Will, K. Tonisch, V. Cimalla, D. Cengher, Christian Haupt, K. Brückner, R. Stephan, M. Hein and O. Ambacher  Micro- and nanomechanical resonators for sensing applications  Due to the combination of mechanical structures with electrically active elements for actuation and sensing, the technology of micro- and nanoelectromechanical systems (MEMS/NEMS) bears a huge potential for sensing applications. Common resonant mass sensors like quartz oscillators operate by providing a frequency shift which is directly proportional to the increase of mass when any kind of material accumulates at its surface. Small active masses enhance the sensitivity for very small mass loadings which leads to a trend of miniaturization into the submicron domain [1]. Reported resonant frequencies up to 1 GHz and quality factors of 10 000 can be achieved only at low temperatures and ultra-high vacuum. For sensing applications, especially biological ones, it is necessary to work under ambient conditions or even in liquids. In this work we demonstrate MEMS and NEMS resonators which operate with a magnetomotive actuation on ambient conditions. This approach paves the way to other sensing applications like examining the viscosity of picoliter-droplets or the detection of single molecules or viruses within a liquid in case of functionalized surfaces [2]. However, the quality factor Q of typical nanomechanical structures is significantly lower than that for the above mentioned macroscopic system (several 100 compared to 100.000) which makes the performance on ambient conditions difficult to achieve. The active layers of MEMS and NEMS were realized using silicon carbide (SiC) deposited by high-vacuum chemical vapor deposition and polycrystalline aluminum nitride (AlN) grown by reactive sputtering on silicon substrates. The top electrode necessary for magnetomotive actuation consists of an evaporated titanium/gold layer system. The resonator design is based on free-standing single- and double-clamped resonators with beam lengths of 10 to 500 µm (fig. 2) and widths of 0.9 to 8 µm [3]. In case of the magnetomotive actuation, the oscillation of the beams is caused by an applied alternating voltage in a permanent magnetic field induced by the Lorenz force. Because of the inherently low read-out voltage a measurement setup was established which separates the excitation signal and the response signal from each other. This method allows to observe the free decay of the oscillations, from which the resonant frequency and quality factor can be derived. 030060090012000 250 500beam length [µm]fres [kHz] SiC AlN The resonators have been characterized on ambient conditions. The resonant frequencies of the AlN and SiC-beams were in the range of 5 to 750 kHz and 0.32 to 2 MHz (fig. 1), respectively. The values of the resonant frequencies were affected by film thickness, beam length and internal homogeneous strain. The quality factors in air reached values up to 350. In order to test the sensitivity of the resonators, an additional mass loading of 50 to 250 pg was applied to AlN-beams of 105 nm thickness by sputtering thin layers of metal. This resulted in a clearly detectable shift of the resonant frequency of about 5%. Similar experiments with SiC-beams and a mass loading of a very thin metal layer indicated a resonant frequency shift of 1.8%, which agrees with calculations based on theoretical models. First observations of oscillations in liquids like propanol showed promising results. Though the amplitude was lowered by damping effects, it remained visible. Thus with an optimized geometry it should be possible to determine the viscosity of surrounding liquids. In addition measurements of resonators with functionalized surfaces will allow to detect molecules or even viruses in liquids. With a controlled growth of nanowires on the basic beam geometries it should also be possible to enable further applications like flow sensors.  This work was supported by the German Science Foundation SPP 1157.  References:    [1] M. L. Roukes, Phys. world 14, 25 (2001) [2] B. Ilic, D. Czaplewski, M. Zalalutinov, and H. G. Craighead, J. Vac. Sci. Technol. B  19, 6 (2001) [3] Ch. Foerster, V. Cimalla, K. Brueckner, V. Lebedev, R. Stephan, M. Hein, O. Ambacher, phys. stat. sol. (a) 202, 4 (2005)  Authors:    Florentina Will, Katja Tonisch, Dr. Volker Cimalla, Dr. Dorin Cengher, Christian Haupt, Klemens Brückner, Ralf Stephan, Prof. Matthias Hein, Prof. Oliver Ambacher Insitute for Micro- and Nanotechnologies; TU Ilmenau; P.O.B. 100565 98693 Ilmenau Phone: 03677 69 3352 Fax: 03677 69 3499 E-mail: florentina.will@tu-ilmenau.de Figure 1: Resonance frequency of AlN and SiC double-clamped beams of different length.  Figure 2: SEM pictures of AlN-based double-clambed beams of different length. 

Micro- and nanomechanical resonators for sensing applications

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Micro- and nanomechanical resonators for sensing applications

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