Authors:
Douglas J. C. Gomes
1
;
Silvia G. Motti
2
and
Paulo B. Miranda
1
Affiliations:
1
Sao Carlos Institute of Physics and University of Sao Paulo, Brazil
;
2
Center for Nano Science and Technology @PoliMi and IIT, Italy
Keyword(s):
Sum-Frequency Generation, Organic Transistors, Electric-Field Poling.
Related
Ontology
Subjects/Areas/Topics:
Mobile Software and Services
;
Nonlinear Optics
;
Optics
;
Photonics
;
Photonics, Optics and Laser Technology
;
Spectroscopy, Imaging and Metrology
;
Telecommunications
;
Wireless Information Networks and Systems
Abstract:
Organic Field-Effect Transistors (OFETs) have attracted much research interest due to their potential for
unique applications, such as flexible electronics. The operation of OFETs depends on the charge
accumulation at the interface between an organic semiconductor and a dielectric material, induced by the
voltage applied at the gate electrode. Direct measurements of the electric-field distribution in an operating
device are useful for proposing and validating theoretical models for OFET operation. Here we propose
using the second-order nonlinear optical process of Sum-Frequency Generation vibrational spectroscopy
(SFG spectroscopy) to probe the presence of an electric-field in the dielectric layer of OFETs, in a noninvasive,
non-destructive and remote fashion. The OFETs were fabricated with a dielectric layer consisting
of poly(methyl-methacrylate) – PMMA, and an active layer based on poly(3-hexyl thiophene) – P3HT, and
SFG spectra were acquired from the channel region of op
erating OFETs. It was observed the appearance of
vibrational bands due to carbonyl groups (~ 1720 cm-1) of the PMMA layer, whose ?(2) were induced by the
electric-field within the dielectric, similarly to a reversible poling of polymers. This phenomenon opens up
the possibility of mapping the spatial charge distribution in the conducting channel using SFG microscopy
in operating devices.
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