tesi R. Miscioscia.pdf - EleA@UniSA

Chapter 4
Morphology-mobility relationship in
dielectrics with optimized surfaceenergy
and its exceptions studied by
means of density of states
Gate-dielectric properties and dielectric-semiconductor interface
physics are known to govern growth of pentacene channel films with a
tremendous impact on the morphology of their polycrystalline phase
[1][2][3][9]; in this context, surface wettability can be considered as a
measure of interface energy properties reflecting on the growth of the
first molecular layers of channel semiconductor on the top of the gate
dielectric layer.
In the scope of the present work there’s the development and
optimization of gate-dielectrics to enhance channel properties and then
device performances.
As a result of the research work, it has been developed a device
based on an organic-inorganic hybrid insulator deposited from
solution phase by sol-gel processing. It has been studied by using an
OTFT as a characterization experiment in comparison with known
results. We found such dielectric layer (named after its acronym
PFTEOS:TEOS) exhibiting anomalous trends in a well-assessed
morphology-mobility relationship.
The nature of this class of OTFTs has been studied by thermal
activation of charge mobility characterizations which showed the
innovative dielectric having a behavior in contrast with common
polymeric gate insulator-based transistors. Such singularity has been
related to density of states in the valence band and to microscopic
disorder which cannot be evaluated by common morphological
characterizations (Scanning Electron Microscope etc.).