The authors report pH -dependent conductance behaviors of single-walled carbon nanotube (SWCNT) multilayer thin-film sensors. SWCNTs are functionalized with carboxylic groups, and layer-by-layer assembled alternatively with polycation, polydiallyldimethyammonium chloride on the microfabricated metal electrodes. Current-voltage (I-V) characteristics show that the conductance of SWCNT multilayer thin-film sensors decreases with increase of pH values. On the other hand, the multilayer resistors with polymethylmethacrylate (PMMA) as a passivation layer demonstrate the increasing conductance with pH, opposite to the case of the absence of PMMA layer. The conductance change in the absence of PMMA attributes to doping/undoping of holes as charge carriers by molecular protonation/deprotonation of p -type semiconducting SWCNTs. With PMMA layer, concentration gradient of hydrogen ions on the dielectric forms the gate bias voltage, which changes the conductance of underlying semiconducting SWCNT layer. Each pH -dependent behavior has versatile applications for chemical and biological detections.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures|
|State||Published - 2009|
Bibliographical noteFunding Information:
This work was partially supported by the DARPA M/NEMS Science and Technology Fundamental Research Program through the Micro/Nano Fluidic Fundamental Focus (MF3) Center. The authors would like to thank the Nanofabrication Center and Characterization Facility at the University of Minnesota for the help with fabrication and characterization.