SWCNT-FET

Semiconductive SWCNT FET transistors capable of operating at room temperature were constructed several years ago and their operation in the terahertz frequency range was predicted [160]. These early devices had p-type characteristics (hole... 

Figure 26.6 Model of geometric gate capacitances for (a) back-gated and (b) electrochemically gated SWCNT-FETs. In the case of back-gating, the geometric capacitance is determined by the capacitance of the Si02 dielectric. During electrochemical gating the electro-...

Figure 26.8 Removal of hysteresis through chemical modification demonstrated hy the hack-gate dependence of conductance of a single s-SWCNT FET (V s =100 mV).

Figure 26.9 Electrochemical gating of SWCNT-FETs covered with two different solid polymer electrolytes (SPEs). The SPEs were spotted from solution on top of the FET surface and heated at 60 °C for an hour. Conductance of the same individual s-SWCNT (F(js = 0.1 V) with two different SPEs is plotted as a function of the voltage at the polymer-electrolyte-gate (Fpec)- An adjacent microfabricated AuPd electrode ( 200 pm distance) on the substrate was...

The implementation of eomplementary logic requires not only p-type but also n-type transistors. Chemieal doping has proven to be a viable approaeh for converting p- into n-type SWCNT-FETs [54, 55], albeit the effieaey laeks sig-... 

Figure 26.16 Scanning photocurrent microscopy (SPCM) of an ambipolar s-SWCNT-FET with data recorded in the p-type (a, c, e) and n-type (b, d, f) regimes. (a, b) SPCM images showing the spatial variation of the photocurrent at zero drain-source bias. An optical image of the device is overlaid in order to identify the position of the contacts (black...

Further to this, the increasing activities in the field of biosensors based upon CNT-FETs could strongly benefit from the development of more elaborate (electro-)chemical functionalisation methods, in particular with regard to achieving ultimate selectivity and biocompatibility [74]. Another stimulating impact may be on the elucidation of the exact mechanism by which SWCNT-FETs detect analytes in solution, specifically whether charge transfer or enhanced carrier scattering is the predominant effect of molecule adsorption [39, 75]. 

The success of FET-based CNT gas sensors quickly attracted interest for use in biosensing applications, particularly since biomolecules such as DNA and proteins are heavily charged under normal conditions. SWCNT FETs are expected to be more sensitive than chemisorbed gas molecules to the binding of such charged species. However, the wet chemical environment with the presence of various ions and other biomolecules makes it much more complicated than gas environments. Studies demonstrated that proteins in the solution tend to adsorb irreversibly onto the bare CNT surface and induce significant change in FET characteristics [67,68]. Thus, extensive efforts have been made to passivate CNT with various polymers, such as PEI, poly(ethylene glycol) (PEG), Nafion, or Tween 20 [67,69,70]. It is conunonly accepted that a polymer or surfactant... 

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