tesi R. Miscioscia.pdf - EleA@UniSA

60 State of the Art
it is important to remember the Halik and Klauk paper published in
2005 on Nature [36] in which a SAM dielectric of only 2.5 nm is
inserted in a benchmark structure, bottom-gate top contacts, made on
silicon wafers.
figure 30: Performance of an organic transistor made by the deposition of a SAM dielectric on
which are grown by vapour phase three molecular layers of pentacene thin film [36].
The figure 30 shows the structure of the transistor made by the
SAM technique to which we are referring. The mobility obtained with
this kind of devices is of the order of 1cm 2 /V*s the on/off ratio about
10 6 and operating voltages in the active region less than 3V.
The natural evolution of SAM dielectrics, as for the above
mentioned high-k insulator, is the multi-layer structure (see figure 31):
we will refer to these systems with a more properly name, Self-
Assembled Multilayer (SAMT) [37]. These dielectrics exhibit very
high gate capacitance (up to 2500nF/cm 2 ) and, like the SAM, may be
deposited from solution on flexible substrates in order to realize both
n-type and p-type transistors [37]. The on/off ratio is still low (about
10 3 ) as often happens in the case of SAM.