Steve Park†, Hang Woo Lee‡, Huiliang Wang†, Selvapraba Selvarasah§, Mehmet R. Dokmeci§, Young Jun Park
, Seung Nam Cha, Jong Min Kim*, and Zhenan Bao‡*
, Seung Nam Cha, Jong Min Kim*, and Zhenan Bao‡*†Department of Materials Science & Engineering and‡Department of Chemical Engineering, Stanford University, Stanford, California 94305, United States
§ Department of Electrical & Computer Engineering,Northeastern University, Boston, Massachusetts 02115, United States
Frontier Research Lab, Samsung Advanced Institute of Technology, KoreaACS Nano, Article ASAP
DOI: 10.1021/nn204875a
Publication Date (Web): February 21, 2012
Copyright © 2012 American Chemical Society
We have verified a highly effective separation of semiconducting single-walled carbon nanotubes (sc-SWNTs) via statistical analysis of short-channel devices fabricated using multipen dip-pen nanolithography. Our SWNT separation technique utilizes a polymer (rr-P3DDT) that selectively interacts with and disperses sc-SWNTs. Our devices had channel lengths on the order of 300–500 nm, with an average of about 3 SWNTs that directly connected the source–drain electrodes. A total of 140 SWNTs were characterized, through which we have observed that all of the SWNTs exhibited semiconducting behavior with an average on/off current ratio of 
106. Additionally, we have characterized 50 SWNTs after the removal of rr-P3DDT, through which we have again observed semiconducting behavior for all of the SWNTs with similar electrical characteristics. The relatively low average on-conductance of 0.0796 μS was attributed to the distribution of small diameter SWNTs in our system and due to the non-ohmic Au contacts on SWNTs. The largely positive threshold voltages were shifted toward zero after vacuum annealing, indicating that the SWNTs were doped in air. To the best of our knowledge, this is the first time numerous SWNTs were electrically characterized using short-channel devices, through which all of the measured SWNTs were determined to be semiconducting. Hence, our semiconducting single-walled carbon nanotube sorting system holds a great deal of promise in bringing forth a variety of practical applications in SWNT electronics.
106. Additionally, we have characterized 50 SWNTs after the removal of rr-P3DDT, through which we have again observed semiconducting behavior for all of the SWNTs with similar electrical characteristics. The relatively low average on-conductance of 0.0796 μS was attributed to the distribution of small diameter SWNTs in our system and due to the non-ohmic Au contacts on SWNTs. The largely positive threshold voltages were shifted toward zero after vacuum annealing, indicating that the SWNTs were doped in air. To the best of our knowledge, this is the first time numerous SWNTs were electrically characterized using short-channel devices, through which all of the measured SWNTs were determined to be semiconducting. Hence, our semiconducting single-walled carbon nanotube sorting system holds a great deal of promise in bringing forth a variety of practical applications in SWNT electronics. 
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