Attenuation of Surface Acoustic Waves by Carbon Nanotubes
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Attenuation of Surface Acoustic Waves by Carbon Nanotubes Daumantas Ciplys1,4, Sergey Rumyantsev1, Michael S. Shur1, Robert Vajtai2, Bingqing Wei2, Pulickel Ajayan2, Remis Gaska3, and Romualdas Rimeika4 1 Department of Electrical, Computer, and Systems Engineering and Center for Integrated Elelectronics, Rensselaer Polytechnic Institute, Troy, NY 12180, U.S.A. 2 Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, U.S.A. 3 Sensor Electronic Technology, Inc., 1195 Atlas Road, Columbia, SC 29209, U.S.A. 4 Department of Radiophysics, Vilnius University, Vilnius 2040, Lithuania
ABSTRACT A strong attenuation of surface acoustic waves in the range of 30 to 100 MHz by singlewalled carbon nanotube layers deposited on the surface of piezoelectric lithium niobate single crystal has been observed. The attenuation exhibits non-monotonous dependence on nanotube density. This attenuation is attributed to the acoustoelectronic interaction between electric fields of the SAW and charge carriers in the nanotubes. The experimental results are in the qualitative agreement with the theory of acoustoelectronic interaction in inhomogeneous structures.
INTRODUCTION The carbon nanotubes (CNTs) have attracted considerable interest due to their onedimensional structure and unique electromagnetic and mechanical properties [1,2]. They also offer a potential to serve as building blocks for future electronic devices [3]. For using the CNTs in different microelectronic devices, the ac behavior becomes important [4]. Investigations of carbon nanotube properties at high frequencies encounter difficulties of electrical contact preparation. The surface acoustic waves (SAWs), which are used in material science as an effective tool for studying the properties of solids and thin layers [5], allow the contactless application of high-frequency electric fields. Therefor, the interaction between a SAW and nanotubes might lead to interesting effects and yield information about nanotube properties [6]. We report on the observation of strong attenuation of surface acoustic waves due to singlewall carbon nanotubes deposited on the surface of piezoelectric crystal. We explain this attenuation in terms of acoustoelectronic interaction.
EXPERIMENTAL DETAILS The SAW attenuation measurements were performed using the YZ-LiNbO3 plate. Three pairs of interdigital transducers (IDTs) for excitation and receiving of surface acoustic waves have been deposited on the plate surface as shown in Fig. 1. Their resonant acoustic wavelengths were 30, 60, and 120 µm, corresponding to SAW frequencies 107, 57, and 28.5 MHz, and the
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NANOTUBES 4 RF INPUT
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Figure 1. Sample configuration; interdigital surface acoustic wave transducers (1-3), electrodes for dc resistance measurements (4). distances between transducers were 12, 17, and 24 mm for pair 1, 2, and 3, respectively. Each transducer had the same aperture width, 1.8 mm, and the same number 15 of the electrode pairs. Transverse elec
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