Web Release Date: October 16,
Photocurrent Imaging of p-n Junctions in Ambipolar Carbon Nanotube Transistors
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Division of Energy Systems Research, Ajou University, Suwon 443-749, Korea, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, Department of Physics and Astronomy, Seoul National University, Seoul 151-742, Korea, and The Rowland Institute at Harvard, Harvard University, Cambridge, Massachusetts 02142
Received June 27, 2007
Revised August 22, 2007
Abstract:
We use scanning photocurrent microscopy (SPCM) to investigate the properties of internal p-n junctions in ambipolar carbon nanotube (CNT) transistors. Our SPCM images show strong signals near metal contacts whose polarity and positions change depending on the gate bias. SPCM images analyzed in conjunction with the overall conductance also indicate the existence and gate-dependent evolution of internal p-n junctions near contacts in the n-type operation regime. To determine the p-n junction position and the depletion width with a nanometer scale resolution, a Gaussian fit was used. We also measure the electric potential profile of partially suspended CNT devices at different gate biases, which shows that induced local fields can be imaged using the SPCM technique. Our experiment clearly demonstrates that SPCM is a valuable tool for imaging and optimizing electrical and optoelectronic properties of CNT based devices.
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