An Equilibrium Based Mean-Field Model for Diffusion in Solids With a Distributed Density of States

1997 ◽  
Vol 469 ◽  
Author(s):  
A. J. Franz ◽  
J. L. Gland
Keyword(s):  
Amorphous Silicon ◽  
Density Of States ◽  
Chemical Potential ◽  
Energy Levels ◽  
Mean Field ◽  
Diffusion In Solids ◽  
Mean Field Model ◽  
Discrete Energy ◽  
Mobile Species

ABSTRACTDetermination of transport mechanisms and energetics in amorphous silicon presents an interesting modeling challenge. Transport in amorphous silicon films is likely to involve energetically distributed traps and mobile species, as in the case of hydrogen and electron diffusion. Detailed kinetic models using discrete energy levels have been developed, however, the density of states of the diffusing species in amorphous silicon is likely to be continuous and distributed, due to the amorphous nature of the films. We have developed a mean-field, equilibrium based model which utilizes a continuous density of states for the diffusing species. The transport in amorphous silicon is modeled as a function of a gradient in the quasi-chemical potential, rather than concentration, of the diffusing species. The model is applicable when the local equilibration processes are fast relative to the transport process. This approach is extremely numerically efficient, as well as flexible, allowing for modeling of tracer experiments, such as deuterium diffusion in a-Si:H films, and possible changes in density of states with time, temperature, and diffusing species concentration. We demonstrate the utility of the model by simulating hydrogen evolution from a-Si:H films.

Determination of Hydrogen Density of States in Amorphous Silicon Using Fractional Evolution Experiments

1997 ◽  
Vol 467 ◽  
Author(s):  
A. J. Franz ◽  
W. B. Jackson ◽  
J. L. Gland
Keyword(s):  
Amorphous Silicon ◽  
Density Of States ◽  
Silicon Film ◽  
Mean Field ◽  
Frequency Factor ◽  
Silicon Films ◽  
Hydrogen Density ◽  
Heating And Cooling ◽  
Novel Method

ABSTRACTHydrogen plays an important role in the electronic behavior, structure and stability of amorphous silicon films. Therefore, determination of the hydrogen density of states (DOS) and correlation of the hydrogen DOS with the electronic film properties are important research goals. We have developed a novel method for determination of hydrogen DOS in silicon films, based on fractional evolution experiments. Fractional evolution experiments are performed by subjecting a silicon film to a series of linear, alternating heating and cooling ramps, while monitoring the hydrogen evolution rate. The fractional evolution data can be analyzed using two complementary memods, the fixed frequency factor approach and Arrhenius analysis. Using a rigorous, mean-field evolution model, we demonstrate the applicability of the two approaches to obtaining the hydrogen DOS in silicon films. We further validate both methods by analyzing experimental fractional evolution data foran amorphous silicon carbide film. Both types of analysis yield a similar double peaked density of states for the a-Si:C:H:D film.

scholarly journals Mean-field model of interacting quasilocalized excitations in glasses

2021 ◽  
Vol 4 (2) ◽  
Author(s):  
Corrado Rainone ◽  
Pierfrancesco Urbani ◽  
Francesco Zamponi ◽  
Edan Lerner ◽  
Eran Bouchbinder
Keyword(s):  
Elastic Medium ◽  
Density Of States ◽  
Field Model ◽  
Mean Field ◽  
Mean Square Displacement ◽  
Decisive Role ◽  
Future Research ◽  
Model Parameters ◽  
Mean Field Model ◽  
Structural Glasses

Structural glasses feature quasilocalized excitations whose frequencies \omegaω follow a universal density of states {D}(\omega)\!\sim\!\omega^4D(ω)∼ω4. Yet, the underlying physics behind this universality is not fully understood. Here we study a mean-field model of quasilocalized excitations in glasses, viewed as groups of particles embedded inside an elastic medium and described collectively as anharmonic oscillators. The oscillators, whose harmonic stiffness is taken from a rather featureless probability distribution (of upper cutoff \kappa_0κ0) in the absence of interactions, interact among themselves through random couplings (characterized by a strength JJ) and with the surrounding elastic medium (an interaction characterized by a constant force hh). We first show that the model gives rise to a gapless density of states {D}(\omega)\!=\!A_{g}\,\omega^4D(ω)=Agω4 for a broad range of model parameters, expressed in terms of the strength of the oscillators’ stabilizing anharmonicity, which plays a decisive role in the model. Then — using scaling theory and numerical simulations — we provide a complete understanding of the non-universal prefactor A_{g}(h,J,\kappa_0)Ag(h,J,κ0), of the oscillators’ interaction-induced mean square displacement and of an emerging characteristic frequency, all in terms of properly identified dimensionless quantities. In particular, we show that A_{g}(h,J,\kappa_0)Ag(h,J,κ0) is a non-monotonic function of JJ for a fixed hh, varying predominantly exponentially with -(\kappa_0 h^{2/3}\!/J^2)−(κ0h2/3/J2) in the weak interactions (small JJ) regime — reminiscent of recent observations in computer glasses — and predominantly decays as a power-law for larger JJ, in a regime where hh plays no role. We discuss the physical interpretation of the model and its possible relations to available observations in structural glasses, along with delineating some future research directions.

Photothermal Investigation of Surfaces and Interfaces in Amorphous Silicon Films

1990 ◽  
Vol 192 ◽  
Author(s):  
G. Amato ◽  
L. Boarino ◽  
Giuliana Benedetto ◽  
R Spagnolo
Keyword(s):  
Amorphous Silicon ◽  
Density Of States ◽  
Theoretical Approach ◽  
Interference Fringe ◽  
Fringe Pattern ◽  
Experimental Results ◽  
Surface And Interface ◽  
Surfaces And Interfaces ◽  
Interference Fringe Pattern

ABSTRACTA method for the determination of surface and interface states is suggested, based on the observation of interference fringe pattern in photo-thermal spectra. Some experimental results are presented and interpreted by means of a theoretical approach. The method allows in most cases to get an evaluation of surface and interface density of states.

scholarly journals STRANGENESS PRODUCTION AT FINITE TEMPERATURE AND BARYON DENSITY IN AN EFFECTIVE RELATIVISTIC MEAN FIELD MODEL

2012 ◽  
Vol 21 (03) ◽  
pp. 1250028
Author(s):  
F. IAZZI ◽  
R. INTROZZI ◽  
A. LAVAGNO ◽  
D. PIGATO ◽  
M. H. YOUNIS
Keyword(s):  
Field Model ◽  
Chemical Potential ◽  
Mean Field ◽  
Baryon Density ◽  
Strangeness Production ◽  
Coupling Scheme ◽  
Mean Field Model ◽  
Relativistic Mean Field ◽  
Kaon Condensation ◽  
Wide Range

We study the strangeness production in hot and dense nuclear medium, by requiring the conservation of the baryon density, electric charge fraction and zero net strangeness. The hadronic equation of state is investigated by means of an effective relativistic mean field model, with the inclusion of the full octet of baryons and kaon mesons. Kaons are considered taking into account of an effective chemical potential depending on the self-consistent interaction between baryons. The obtained results are compared with a minimal coupling scheme, calculated for different values of the anti-kaon optical potential and with noninteracting kaon particles. In this context, we also consider the possible onset of the kaon condensation for a wide range of temperatures and baryon densities.

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