Failure of Arrhenius plots for investigation of localized levels

Abstract

2014 L'étude de l'ionisation Poole Frenkel, lorsque les niveaux localisés sont distribués en bandes, est réalisée en prenant la température T comme variable. Un grand nombre de simulations a révélé le même comportement qualitatif des diagrammes d'Arrhénius de la conductivité (log 03C3, 1/T), que celui présenté par un seul niveau. De nombreux exemples sont traités, pour montrer clairement que des portions linéaires étendues peuvent être obtenues sur les courbes, quelle que soit la largeur de la distribution. En conséquence, les énergies d'activation, déduites de ces diagrammes, ne peuvent plus être assignées à un niveau d'énergie réel quelconque. Nous croyons avoir montré que, poser comme principe que les niveaux d'un système à niveaux multiples peuvent toujours être séparés en leurs composantes, est en contradiction avec la statistique de Fermi-Dirac.

Electrical Conductivity and Dielectric Properties of Solid Asphaltenes

“…First, as noted above, this model accounts for not only transport of free (collectivized) charge carriers and unidirectional hopping of localized carriers between spatially neighboring traps but also a “random walk” hopping of carriers between traps close in energy but of variable distances away from each other. Second, Arrhenius-type models are known to account primarily for “shallow” traps in the band tails, while the VRH model also accounts for “deep” traps near the middle of the energy gap. , Third, the use of the Arrhenius-type approach and the concept of activation energy seems to rely on an apparently common sense principle, that of “splittability of energy levels”, which is not always working . Well-splitted levels of localized traps may be expected to arise from dopants and impurities, while traps from structural disorder commonly possess a practically uniform (non-splitted) distribution of states. ,, …”

“…Second, Arrhenius-type models are known to account primarily for “shallow” traps in the band tails, while the VRH model also accounts for “deep” traps near the middle of the energy gap. , Third, the use of the Arrhenius-type approach and the concept of activation energy seems to rely on an apparently common sense principle, that of “splittability of energy levels”, which is not always working . Well-splitted levels of localized traps may be expected to arise from dopants and impurities, while traps from structural disorder commonly possess a practically uniform (non-splitted) distribution of states. ,, …”

“…44,45 Third, the use of the Arrheniustype approach and the concept of activation energy seems to rely on an apparently common sense principle, that of "splittability of energy levels", which is not always working. 52 Wellsplitted levels of localized traps may be expected to arise from dopants and impurities, while traps from structural disorder commonly possess a practically uniform (non-splitted) distribution of states. 44,52,53 Summarizing, the results discussed in this section suggest a presence of both "bulk" and "surface" electron conductivity in asphaltenes, with the latter being predominant in powder (dispersed) samples.…”

“…52 Wellsplitted levels of localized traps may be expected to arise from dopants and impurities, while traps from structural disorder commonly possess a practically uniform (non-splitted) distribution of states. 44,52,53 Summarizing, the results discussed in this section suggest a presence of both "bulk" and "surface" electron conductivity in asphaltenes, with the latter being predominant in powder (dispersed) samples. In turn, three types of electron transport mechanisms, mentioned above, may be distinguished.…”