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Localization: Self-Trapping
Published in Yuzo Shinozuka, Electron-Lattice Interactions in Semiconductors, 2021
In Chapter 2, we have seen that the interaction between a carrier and the crystal phonons makes them a compound quasiparticle, polaron. The character of a polaron is classified into two types: large polaron and small polaron. A large polaron is realized when the electron–lattice (e–L) interaction is weak, where the wave function of an electron extends over large area and accompanied lattice distortion is weak. When the electron–lattice interaction is strong, a small polaron is realized where the extension of the electron wave function is small and accompanied lattice distortion is strong. In this chapter, we further discuss self-trapping of a carrier in semiconductors in two different approaches: One is the effective mass approximation with a continuum model and the other is a tight binding approach with a discrete model. Finally, we discuss the photoabsorption and photoemission processes in connection with self-trapping.
Electrochromism And Electrochromic Devices
Published in P.J. Gellings, H.J.M. Bouwmeester, Electrochemistry, 2019
The t2g band is almost full in IrO2, RhO2, delithiated LiCoO2, and, possibly, deprotonated Ni(OH)2 (the latter materials were referred to as “CoO2” and “NiO2” in Table 16.1). These oxides are strongly absorbing. Polaron absorption is not observed, and intraband absorption in a composite material characterized by parts having various electron densities (conductivities) and shapes is a more likely cause for the optical behavior. In principle, effective medium theory40 could account for the optical properties, but in the absence of substantial evidence for a composite structure the proposed absorption mechanism must be regarded as conjectural. Electron insertion, associated with a filling of t2g band, leads to optical transparency, as noted above.
Mechanism in charge transfer and electrical stability
Published in Ze Zhang, Mahmoud Rouabhia, Simon E. Moulton, Conductive Polymers, 2018
Wen Zheng, Jun Chen, Peter C. Innis
Conductivity in ICPs is attributed to the presence of charge carriers, which are typically p-type polarons, bipolarons in nondegenerate ICPs, or solitons in degenerate PA (Bredas and Street 1985). The observed electrical conductivity can be described by semiconductor theory incorporating electron–lattice or electron–electron interactions (Baeriswyl et al. 1992), which are free to move along the conjugated polymer backbone of the ICP as a result of π-bond delocalization. In chemical terminology, polarons and bipolarons correspond to stable un-spin-paired radical cations and spinless divalent cations, respectively. Solitons arise from bond alternation defects or misfits in polyenes and only exist in degenerate polymer systems such as PA (Figure 4.4). Under an electrical field, the movement of polarons and bipolarons conducts charge.
Synthesis and characterization of NiZnO nanoparticles
Published in Inorganic and Nano-Metal Chemistry, 2018
Chinnasamy Thangamani, Kuppusamy Pushpanathan
Variation of ac electrical conductivity of NiO sample studied at various temperatures is shown in the Figure 10(c). It can be seen that the conductivity remains constant at low frequency but for higher frequency the conductivity increases. NiO is probably a defect semiconductor due to absorption of oxygen. Here cation vacancy produces holes in the valence band. Electrical conductivity is caused by the polaron conduction i.e., highly localized carriers bound to the lattice with an accompanying lattice strain.
Erbium-doped GeSbSe glassy semiconductors and theoretical analysis of constraint, electronic and thermal properties
Published in Phase Transitions, 2021
Chandresh Kumari, S. C. Katyal, Pankaj Sharma
Polaron is a quasiparticle that basically defines the interaction of electrons, how electrons interact with atom in solids. Electrons do have a lattice distortion within that allow them to move from one place to other. Polaron formation reduces electron mobility in a semiconductor. With the addition of atoms, the size of the polaron should reduce. The polaron radius is determined utilizing the relation [36]
Some characterizations of a new metal–organic framework (n-C14H29NH3)2CdCl4 and the role of hydrogen bonding
Published in Phase Transitions, 2018
In general, when a conduction electron moving through a primarily ionic solid, it polarizes and distorts the lattice in its vicinity. A polaron consists of the charge carrier and the distortion of the ionic lattice induced by the carrier itself. We have two types of polarons: small polaron and large polaron and hence there are two models.