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Electrophoretic Deposition of Single Wall Carbon Nanotube Films and Characterization Junyoung Lim, Maryam Jalali, Stephen A. Campbell Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455, U.S.A.

ABSTRACT Electrophoretic deposition enables the rapid deposition of single wall carbon nanotube films at room temperature. An accurate, reproducible film thickness can be obtained by controlling electric field strength, suspension concentration, and time. To investigate the electrical and mechanical properties of such films, we recorded electric resistance and Young’s modulus using I-V characterization and a nanoindenter, respectively. The measured resistivity of the films varied from 2.14  10-3 to 7.66  10-3 Ωcm, and the Young’s modulus was 4.72 to 5.67 GPa, independent of film thickness from 77 to 134 nm. These results indicated that the mechanical and electrical properties of film are comparable with previously reported methods such as layer by layer deposition even though we achieved much higher deposition rates. We also measured the film mass density which is usually unrecorded even though it is an important parameter for MEMS/NEMS device actuation. The film density was found with conventional thickness measurement and Rutherford backscattering spectrometry. It varied from 0.12 to 0.54 g/cm3 as the film thickness increased. This method could be extended to applications of CNT films for flexible electronics or high frequency RF MEMS devices. INTRODUCTION Carbon nanotubes (CNTs) represent a nearly ideal material for enabling high performance micro/nano-electromechanical (MEMS/NEMS) devices because of their extraordinary mechanical and electrical properties [1]. The mechanical properties of carbon nanotubes allow one to make MEMS devices that operate at extremely high speed with a potential for far lower power dissipation than conventional CMOS device [2]. Early device demonstrations used discrete CNTs placed randomly until one happened to bridge a pair of electrodes. More recently, techniques for depositing continuous films of CNTs have been investigated. This approach allows the use of standard lithography and etching processes to produce arbitrary patterns at any desired location on a substrate. In order to grow continuous CNT films, high temperature process such as chemical vapor deposition is often required. These processes are incompatible with many substrates including metallized wafers. A low-temperature (< 300 oC) CNT film deposition process such as electrophoretic deposition (EPD) is well suited to fabricate continuous CNT films even on flexible substrates. EPD is a low-cost and versatile processing method for room temperature deposition of CNTs [3]. EPD uses the motion of charged particles which are dispersed in suspension under an applied electric field [4]. This method can be used to deposit thin and thick films, and composite coatings with complex shapes and surface patterns [5]. Here we report on the deposition process of CNT film using EPD processing and the electrical/mec