tesi R. Miscioscia.pdf - EleA@UniSA

Chapter 2 75
One interesting character of PANI is its qualitatively different
behaviour respect to Gold when employed for contacts. In fact, as
reported by Blanchet et al. in [49], the output characteristics in linear
regime of a BC-OTFT using PANI contacts show ohmic trend, while
the corresponding TC-OTFT acts differently (see figure 45).
figure 45: left, output characteristics in linear regime of a BC-OTFT with PANI S and D; right, the
corresponding TC-OTFT. Both devices use pentacene semiconductor [49]
2.7.3 Composite materials for Source and Drain
electrodes
Composite materials, as Gate insulator and as electrodes, are
one of the approaches employed to improve the OTFT performances.
In paragraph 2.7.1.3, we have already seen that a dispersion of Gold
nanoparticles can be applied to fabricate patterned electrodes.
Also Carbon nanotubes are quite often applied. For example,
in [57], a dispersion of Single-Walled NanoTubes (SWNT) is
deposited using spin-coating technique. To have contacts conductive
enough to be employed in OTFTs, but not increasing the SWNT
concentration beyond the percolation limit (and other important
effects), authors apply the self-assembling of a matrix of poly(styreneblock-4vinylpyridine)
(PS-b-P4VP) doped with HAuCl4.3H2O and
with SWNT dispersed into, to increase electrical conductivity and not
reduce film transparency.
In figure 46, clear field TEM images are shown for a stabilized
film (a) and at the highest possible concentration of doping (b). In (c),