Showing papers by "Vittorio Romano published in 2001"

Non‐parabolic band hydrodynamical model of silicon semiconductors and simulation of electron devices

Abstract: A consistent hydrodynamical model for electron transport in silicon semiconductors, free of any fitting parameter, has been formulated in Anile and Romano (Continuum Mechanics Thermodynamics 1999; 11:307–325) and Romano (Continuum Mechanics Thermodynamics 1999; 12:31–51) on the basis of the maximum entropy principle, by considering the energy band described by the Kane dispersion relation. Explicit constitutive functions for fluxes and production terms in the macroscopic balance equations of density, crystal momentum, energy and energy flux have been obtained. Scatterings of electrons with non-polar optical phonons (both for intervalley and intravalley interactions), acoustic phonons and impurities have been taken into account. In this article we show the link with other macroscopic models describing the motion of charge carriers. In particular, under suitable scaling assumptions, an energy transport model is recovered. An analysis of the formal properties is given by showing that the evolution equations form a hyperbolic system in the physically relevant region of the space of the dependent variables. At last, by using the numerical method developed in Liotta et al. (International Series of Numerical Mathematics 1999; 130:651–660) and Liotta et al. (SIAM Journal on Numerical Analysis 1999, to appear) simulations for bulk silicon and n+–n–n+ silicon diode are performed. The obtained results are in good agreement with the Monte Carlo data. Copyright © 2001 John Wiley & Sons, Ltd.

Simulation of Submicron Silicon Diodes with a Non-Parabolic Hydrodynamical Model Based on the Maximum Entropy Principle

Abstract: A hydrodynamical model for electron transport in silicon semiconductors, free of any fitting parameters, has been formulated in [1,2] on the basis of the maximum entropy principle, by considering the energy band described by the Kane dispersion relation and by including electron-non polar optical phonon and electron-acoustic phonon scattering.

Relation between growth dynamics and diffusional limitations in Saccharomyces cerevisiae cells growing as entrapped in an insolubilised gelatin gel

Abstract: Flow-cytometric analysis was employed to investigate growth dynamics of a yeast cell population immobilised in an insolubilised gelatin gel by means of the quantitative determination of the average protein content per cell. This analysis was carried out on both the immobilised cell population considered as a whole and the subpopulations colonising the gelatin matrix at different depths. The results show that growth of the gelatin-immobilised yeast population was affected by the existence of a gradient of nutrient concentrations through the matrix and are in agreement with the unsteady-state diffusion model employed for the description of glucose transfer in the gel.

Stability of the equilibrium state for a hydrodynamical model of charge transport in semiconductors

Abstract: Lyapunov stability and, under a certain restriction on the doping density, asymptotic stability of the equilibrium state for the hydrodynamical model of charge transport in semiconductors based on Extended Thermodynamics [1, 2, 3] is proved in the linear approximation for a typical one dimensional problem.

Numerical Investigation of Shock Waves in a Radiating Gas Described by a Variable Eddington Factor

Abstract: Recently a numerical method suitable for dealing with hyperbolic systems of conservation laws also in the presence of source terms, both in stiff and non-stiff case, has been developed (Liotta et al, 1999a, b) Here we use such a scheme for getting numerical solutions of the shock structure problem for the model of a radiating gas described by a variable Eddington factor (Anile et al, 1991, 1992; Kremer and Muller, 1992) in the framework of extended thermodynamics

Asymptotic Waves in the Hydrodynamical Model of Semiconductors Based on Extended Thermodynamics

Abstract: An analysis of asymptotic wave solutions for the hydrodynamical model of semiconductors based on Extended Thermo-dynamics [1, 2, 3, 4] is presented. The evolution equations form a quasilinear hyperbolic system, coupled to the Poisson equation for the electric potential. The aim of this article is to describe the far field for such a model by a suitable adaptation of the asymptotic expansion proposed in [5, 6, 7]. The stationary solution for uniformly doped semiconductor has been taken as unperturbed state. We distinguish two cases: perturbations with wavelength smaller than the scaled Debye length and perturbations of the same order of the Debye length. In the first case the perturbation of the electric field is negligible and the resulting model equation exhibits nonlinear and relaxation effects. In the second case a drift term due to the presence of a non negligible perturbation of the electric field arises as well.