Short-channel effects simulation

In Fig. 2 are shown the I-V characteristics of a 12 pm channel length a-6T FET together with calculated characteristics using Eqs (3) and (4) and it can be observed that the agreement between data and the simulation is good. At such channel lengths, short-channel effects are negligible. 

We fabricated organic transistors with channel lengths L < 1 [im using only a few simple technological steps which are used in microelectronics [42, 43]. In order to avoid short-channel effects from the very beginning, necessary design parameters have been estimated by numerical two-dimensional simulations. 

Another way to avoid the short-channel effect is to use a Schottky contact at drain, as proposed in [51 ]. However, our simulation has shown that this is connected with a strong reduction of the drain current [52]. Therefore, this approach must be excluded for practical applications. 

Low-cost polymer films are typically realized by solution-based technology. The resulting hole mobilities, however, lie below that of vapor deposited layers. Consequently, the performance of solution-based organic field effect transistors is limited. In Chap. 6, Susanne Scheinert and Gernot Paasch address the problems of low-cost sub-micrometer devices and present experimental results, contact problem simulations, and simulations of short-channel effects, which lead to short-channel design rules. 

The QM/MM and ab initio methodologies have just begun to be applied to challenging problems involving ion channels [73] and proton motion through them [74]. Reference [73] utilizes Hartree-Fock and DFT calculations on the KcsA channel to illustrate that classical force fields can fail to include polarization effects properly due to the interaction of ions with the protein, and protein residues with each other. Reference [74] employs a QM/MM technique developed in conjunction with Car-Parrinello ab initio simulations [75] to model proton and hydroxide ion motion in aquaporins. Due to the large system size, the time scale for these simulations was relatively short (lOps), but the influences of key residues and macrodipoles on the short time motions of the ions could be examined. 

There are many chemically reacting flow situations in which a reactive stream flows interior to a channel or duct. Two such examples are illustrated in Figs. 1.4 and 1.6, which consider flow in a catalytic-combustion monolith [28,156,168,259,322] and in the channels of a solid-oxide fuel cell. Other examples include the catalytic converters in automobiles. Certainly there are many industrial chemical processes that involve reactive flow tubular reactors. Innovative new short-contact-time processes use flow in catalytic monoliths to convert raw hydrocarbons to higher-value chemical feedstocks [37,99,100,173,184,436, 447]. Certain types of chemical-vapor-deposition reactors use a channel to direct flow over a wafer where a thin film is grown or deposited [219]. Flow reactors used in the laboratory to study gas-phase chemical kinetics usually strive to achieve plug-flow conditions and to minimize wall-chemistry effects. Nevertheless, boundary-layer simulations can be used to verify the flow condition or to account for non-ideal behavior [147]. 

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