Manipulation of charge carrier injection into organic field-effect transistors by self-assembled monolayers of alkanethiols Asadi, Kamal; Gholamrezaie, Fatemeh; Smits, Edsger C. P.; Blom, Paul W. M.; de Boer, Bert
The threshold voltage is an important property of organic field-effect transistors. By applying a self-assembled monolayer (SAM) on the gate dielectric, the value can be tuned. After electrical characterization, the semiconductor is delaminated. The surface potentials of the revealed SAM perfectly agree with the threshold voltages, which demonstrate that the shift is not due to the dipolar contribution, but due to charge trapping by the SAM.
This work describes n‐type self‐assembled monolayer field‐effect transistors (SAMFETs) based on a perylene derivative which is covalently fixed to an aluminum oxide dielectric via a phosphonic acid linker. N‐type SAMFETs spontaneously formed by a single layer of active molecules are demonstrated for transistor channel length up to 100 μm. Highly reproducible transistors with electron mobilities of 1.5 × 10−3 cm2 V−1 s−1 and on/off current ratios up to 105 are obtained. By implementing n‐type and p‐type transistors in one device, a complimentary inverter based solely on SAMFETs is demonstrated for the first time.
Quinquethiophene-based monolayer organic field-effect transistors (OFETs) prepared by Langmuir-Blodgett (LB) technique show hole mobilities up to 10−2 cm2/Vs and On/Off ratios up to 106. Functional logic LB monolayer devices operating in air have been demonstrated. The performance of LB OFETs is comparable to self-assembled monolayer field-effect transistors (SAMFETs) devices prepared by self-assembly from solution using the same organosilicon oligothiophene despite the LB OFET monolayer is weakly bounded to the dielectric surface. Taking into account that the LB technique is a fast and rather easy process, these findings highlight a high potential of LB technique for ultrathin organic electronics.
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