title: Ultrahigh density alignment of carbon nanotube arrays by dielectrophoresis.
abstract: We report ultrahigh density assembly of aligned single-walled carbon nanotube (SWNT) two-dimensional arrays via AC dielectrophoresis using high-quality surfactant-free and stable SWNT solutions. After optimization of frequency and trapping time, we can reproducibly control the linear density of the SWNT between prefabricated electrodes from 0.5 SWNT/μm to more than 30 SWNT/μm by tuning the concentration of the nanotubes in the solution. Our maximum density of 30 SWNT/μm is the highest for aligned arrays via any solution processing technique reported so far. Further increase of SWNT concentration results in a dense array with multiple layers. We discuss how the orientation and density of the nanotubes vary with concentrations and channel lengths. Electrical measurement data show that the densely packed aligned arrays have low sheet resistances. Selective removal of metallic SWNTs via controlled electrical breakdown produced field-effect transistors with high current on-off ratio. Ultrahigh density alignment reported here will have important implications in fabricating high-quality devices for digital and analog electronics.
authors.affiliation: Nanoscience Technology Center, Department of Physics, School of Electrical Engineering and Computer Science, University of Central Florida, Orlando, FL 32826, USA.
authors.forename: Shashank
authors.initials: S
authors.lastname: Shekhar
authors.forename: Paul
authors.initials: P
authors.lastname: Stokes
authors.forename: Saiful I
authors.initials: SI
authors.lastname: Khondaker
mesh_terms: D003460:Crystallization / Q000379:methods*; D004586:Electrophoresis / Q000379:methods*; D004595:Electroplating / Q000379:methods*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D036103:Nanotechnology / Q000295:instrumentation; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D013499:Surface Properties; D014173:Transistors, Electronic
chemical_list: D046911:Macromolecular Substances; D037742:Nanotubes, Carbon