Testing With Bars From Dynamic to Quasi-static

International audienceThe numerical calculation of the dynamic loading of a structure includes a great number of steps in which various fundamental or engineering problems are involved. Most of them are addressed in the present course at CISM. In this paper, we discuss the testing of materials in order to model their behaviour

Trap-limited transport in rubrene transistors

The charge carrier mobility in the transport channel of an organic transistor is estimated within the framework of a trap-and-release model. The model accounts for the observed dependence of the mobility on the dielectric constant "epsilon" of the gate insulator. This dependence is attributed to both the effective mass of the carrier and the energetic depth of transport traps due to interface defects being functions of "epsilon". These results are used to describe the critical role of the interface between the organic semiconductor and the dielectric material in governing charge transport in organic transistors

Charge transport mechanisms in microcrystalline silicon

A heterogeneous charge transport model for microcrystalline silicon based on fluctuation-induced tunneling is presented that fits the low-temperature saturation observed in dark conductivity measurements and accounts for the film microstructure. Excellent agreement is found when the model is applied to data reported in the literature, particularly for highly crystalline samples, which produce the highest performance transistors. Values obtained for the three fitting parameters are consistent with typical measurements of microcrystalline silicon film morphology and the conduction band offset between amorphous and crystalline silicons

Hopping and trapping mechanisms in organic field-effect transistors

A charge carrier in the channel of an organic field-effect transistor (OFET) is coupled to the electric polarization of the gate in the form of a surface Fröhlich polaron [N. Kirova and M. N. Bussac, Phys. Rev. B 68, 235312 (2003)]. We study the effects of the dynamical field of polarization on both small-polaron hopping and trap-limited transport mechanisms. We present numerical calculations of polarization energies, band- narrowing effects due to polarization, hopping barriers, and interface trap depths in pentacene and rubrene transistors as functions of the dielectric constant of the gate insulator and demonstrate that a trap-and-release mechanism more appropriately describes transport in high-mobility OFETs. For mobilities on the order 0.1 cm^2/V s and below, all states are highly localized and hopping becomes the predominant mechanism

Numerical model for injection and transport in multilayers OLEDs

International audienceWe present a recently developed numerical code for OLED simulation. This code contains a detailed description of contacts, charge transport and recombination. Its efficiency is briefly shown through examples of single- and bilayer devices and discussed in more detail through the investigation of the action of a LiF thin film on injection. In particular, we show how the code can help to discriminate between several possible explanations for this phenomeno

Sawtooth stabilization by energetic trapped particles

Recent experiments involving high power radio-frequency heating of a tokamak plasma show strong suppression of the sawtooth oscillation. A high energy trapped particle population is shown to have a strong stabilizing effect on the internal resistive kink mode. Numerical calculations are in reasonable agreement with experiment. 13 refs., 2 figs

Influence of an energetic ion population on Tokamak plasma stability

Submitted to Physics of FluidsSIGLEITItal

MOLED: Simulation of multilayer organic light emitting diodes

International audienc