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Low‐Operating‐Voltage Organic Transistors Made of Bifunctional Self‐Assembled Monolayers
Author(s) -
Mottaghi M.,
Lang P.,
Rodriguez F.,
Rumyantseva A.,
Yassar A.,
Horowitz G.,
Lenfant S.,
Tondelier D.,
Vuillaume D.
Publication year - 2007
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200600179
Subject(s) - materials science , bifunctional , monolayer , self assembled monolayer , thin film transistor , optoelectronics , alkyl , organic electronics , transistor , nanotechnology , organic semiconductor , threshold voltage , layer (electronics) , voltage , organic chemistry , chemistry , electrical engineering , catalysis , engineering
Self‐assembled monolayers (SAMs) are molecular assemblies that spontaneously form on an appropriate substrate dipped into a solution of an active surfactant in an organic solvent. Organic field‐effect transistors are described, built on an SAM made of bifunctional molecules comprising a short alkyl chain linked to an oligothiophene moiety that acts as the active semiconductor. The SAM is deposited on a thin oxide layer (alumina or silica) that serves as a gate insulator. Platinum–titanium source and drain electrodes (either top‐ or bottom‐contact configuration) are patterned by using electron‐beam (e‐beam) lithography, with a channel length ranging between 20 and 1000 nm. In most cases, ill‐defined current–voltage ( I–V ) curves are recorded, attributed to a poor electrical contact between platinum and the oligothiophene moiety. However, a few devices offer well‐defined curves with a clear saturation, thus allowing an estimation of the mobility: 0.0035 cm 2 V –1 s –1 for quaterthiophene and 8 × 10 –4 cm 2 V –1 s –1 for terthiophene. In the first case, the on–off ratio reaches 1800 at a gate voltage of –2 V. Interestingly, the device operates at room temperature and very low bias, which may open the way to applications where low consumption is required.