Interpretation of diffusion coefficients in nanostructured materials from random walk numerical simulation
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Other documents of the author: Anta, Juan A.; Dittrich, Thomas; Bisquert, Juan; Mora-Sero, Ivan
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Show full item recordcomunitat-uji-handle:10234/9
comunitat-uji-handle2:10234/2507
comunitat-uji-handle3:10234/6973
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Title
Interpretation of diffusion coefficients in nanostructured materials from random walk numerical simulationDate
2008Publisher
Royal Society of ChemistryISSN
14639076Type
info:eu-repo/semantics/articleVersion
info:eu-repo/semantics/acceptedVersionAbstract
We make use of the numerical simulation random walk (RWNS) method to compute the ‘‘jump’’
diffusion coefficient of electrons in nanostructured materials via mean-square displacement. First,
a summary of analytical ... [+]
We make use of the numerical simulation random walk (RWNS) method to compute the ‘‘jump’’
diffusion coefficient of electrons in nanostructured materials via mean-square displacement. First,
a summary of analytical results is given that relates the diffusion coefficient obtained from RWNS
to those in the multiple-trapping (MT) and hopping models. Simulations are performed in a
three-dimensional lattice of trap sites with energies distributed according to an exponential
distribution and with a step-function distribution centered at the Fermi level. It is observed that
once the stationary state is reached, the ensemble of particles follow Fermi–Dirac statistics with a
well-defined Fermi level. In this stationary situation the diffusion coefficient obeys the theoretical
predictions so that RWNS effectively reproduces the MT model. Mobilities can be also computed
when an electrical bias is applied and they are observed to comply with the Einstein relation when
compared with steady-state diffusion coefficients. The evolution of the system towards the
stationary situation is also studied. When the diffusion coefficients are monitored along simulation
time a transition from anomalous to trap-limited transport is observed. The nature of this
transition is discussed in terms of the evolution of electron distribution and the Fermi level. All
these results will facilitate the use of RW simulation and related methods to interpret steady-state
as well as transient experimental techniques [-]
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