Gate Dielectric Layers

There are some important demands for gate dieleetries in organic field effect transistors. For example  

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The gradual channel approximation (described above) may fail, as the channel length of the FET is shortened. The electrostatics of the FET limit L > 1.5 q in a molecular FET, where the dielectric constant of the gate dielectric layer and semiconductor channel may be similar [22, 23]. This is particularly important in monolayer transistors, as many monolayer FETs studied have been limited to tens of nanometers channel length by the tens of nanometers size of ordered domains, and therefore require thin gate dielectric layers. Only recently (described below) have routes been shown to form more extended ordered molecular monolayers, allowing micron-scale FET channel lengths to be explored. 

Three-methods have been pursued to organize monolayers from different organic compounds to form molecular monolayer FETs (1) thermal evaporation of approximately monolayer thickness on the dielectric surface of FETs, (2) Langmuir-Blodgett assembly on the water surface and transfer to device surfaces, and (3) self-assembly of functionalized organic compounds on the surface of the gate, or gate dielectric layers of FETs. 

Fig. 11 (a) Schematic of an a-substituted quinquethiophene liquid crystalline monolayer assembled on an SU8 organic gate dielectric layer of an FET. (b) Transfer characteristics in the linear and saturation regimes for a 20 pm channel length monolayer FET fabricated (inset) in a ring geometry... 

Fig. 13 Monolayer KETs assembled on SU8 organic gate dielectric layers configured to form different circuits, (a) dc transfer characteristics of an inverter at different supply voltages (Rdd) (b) output characteristics of a 7-stage ring oscillator, and (c) output of a 4-bit code generator (continuous line) and the preprogrammed code (dotted line)...

An OTFT comprises three electrodes (source, drain, and gate), a gate dielectric layer, and an organic or polymer semiconductor layer. In operation, an electric field is applied across the source-drain electrodes, and the transistor is turned on when a voltage (VG) is applied to the gate electrode, which induces a current flow (fD) from the source electrode to drain electrode. When VG = 0, the transistor is turned off, fD should in theory be 0, that is, no current is flowing. 

Besides the general insulating properties of insulating materials, chemical and thermal stability is required and excellent film-forming properties and methods for patterning the insulating layer. Therefore, the most common polymers (e.g. polyethylene, polypropylene, polyvinylchloride etc.) have not yet been used as gate-dielectric layers. 

Using TFTs with thermally cross-linked PVP as gate-dielectric layer a wide range of integrated circuits have been demonstrated. By building on coplanar bottom-... 

Compared with conventional photolithography, laser drilling is a dry process and keeps the surface of polyimide gate dielectric layer away from water, etching solution, or other solvent, which often degrade the polyimide surface. We have confirmed that the electronic performance of transistors with laser via holes is identical with that without laser via holes. 

Polymer electronics on foils require mechanically flexible gate dielectric layers. Unfortunately, inorganic insulating films suffer from high deposition temperatures and a lack of mechanical elasticity. In a first step the inorganic gate dielectric is substituted by a polymer film, still using a silicon substrate because of their smooth and well-known surface. 

In summary, the measured results confirmed that the gate dielectric layer at the pentacene/dielectric interface is essential origins, which considerably influenced the carrier transport phenomena and achievable drain current of pentacene OFETs. 

Cui, T.H. and Liang, G.R., Dual-gate pentacene organic field-effect transistors based on a nanoassembled SiOj nanoparticle thin film as the gate dielectric layer, Appl. Phys. Lett. 86 (6), 064102, 2005. 

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