Novel transistors and logic devices based on nanotechnology concepts are under intense development. The potential for ultra-low-power circuitry makes nanotechnology attractive for applications such as digital electronics and sensors. For NASA applications, nanotechnology offers tremendous opportunities for increased onboard data processing, and thus autonomous decisionmaking ability, and novel sensors that detect and respond to environmental stimuli with little oversight requirements. Polyaniline/polyethylene oxide (PANi/PEO) nanofibers are of interest because they have electrical conductivities that can be changed from insulating to metallic by varying the doping levels and conformations of the polymer chain.
Scanning electron microscope image of electro-spun PANi/PEO fibers over a prepatternedSi/SiO2 substrate.
Long description.
At the NASA Glenn Research Center, we have observed field effect transistor (FET) behavior in electrospun PANi/PEO nanofibers doped with camphorsulfonic acid. The nanofibers were deposited onto Au electrodes, which had been prepatterned onto oxidized silicon substrates. The preceding scanning electron image shows the device used in the transistor measurements. Saturation channel currents are observed at surprisingly low source/drain voltages (see the following graph). The hole mobility in the depletion regime is 1.4×10-4 cm2/V·sec, whereas the one-dimensional charge density (at zero gate bias) is calculated to be approximately 1 hole per 50 two-ring repeat units of polyaniline, consistent with the rather high channel conductivity (~10-3 S/cm). Reducing or eliminating the PEO content in the fiber is expected to enhance device parameters. Electrospinning is thus proposed as a simple method of fabricating one-dimensional polymer FET's.
Current-voltage characteristics of the FET device. Inset: Current-voltage characteristics of the device with no applied back gate voltage.
Long description.
Glenn contacts: Noulie Theofylaktos, 216-433-2702, Onoufrios.Theofylaktos-1@nasa.gov;
Daryl C. Robinson, 216-433-3553, Daryl.C.Robinson@nasa.gov; and Dr.
Félix A. Miranda, 216-433-6589, Felix.A.Miranda@nasa.gov
Analex contact: Dr. Carl H. Mueller, 216-433-8853, Carl.H.Mueller@grc.nasa.gov
Authors: Dr. Carl H. Mueller, Onoufrios Theofylaktos, Daryl C. Robinson, and Dr. Félix A. Miranda
Headquarters program office: OAT
Programs/Projects: DDF, Space Science--such as Magnetospheric
Constellation, Deep Space Probes(e.g., missions to Mars and Jupiter)
Last updated: January 20, 2005
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