Valence-Alternation Model for Localized Gap States in Lone-Pair Semiconductors

Kastner, M. A.; Adler, David; Fritzsche, H.

doi:10.1103/physrevlett.37.1504

Cited by 1,283 publications

(444 citation statements)

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“…It is during the analysis of charged defects in the parent structure that we will be able to make a connection between the present approach and the much earlier specific proposals on the defect states in chalcogenides. 40,41 The large spatial extent of the malcoordination-based states is a result of the lattice's attempt to mitigate the energy cost of what would have been a local defect in the parent structure. The converse is also true: According to Eq.…”

Section: The Charge On the Coordination Defects And The Relation Tmentioning

confidence: 99%

“…12, including Ch + 3 , Ch − 3 , Ch + 1 , and Pn + 4 , have been proposed as relevant defect species earlier, based on the putative presence of dangling bonds 40,41 vector-type chargedensity waves, 42 and molecular dynamics studies using energies determined by tight-binding methods. 43 Specifically in the venerable approach of Kastner et al 40 , pairs of defects, called valence-alternation pairs (VAP), could spontaneously arise in glass because of a presumed instability of a pair of dangling bonds toward creation of two charged defects: 2Ch 0 3 →Ch + 3 +Ch − 1 or 2Pn 0 4 →Pn + 4 +Ch − 1 . Despite common features with the VAP theory, the present picture is distinct in several key aspects, in addition to the aforementioned ones.…”

Section: The Charge On the Coordination Defects And The Relation Tmentioning

confidence: 99%

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Electronic structure and the glass transition in pnictide and chalcogenide semiconductor alloys. II. The intrinsic electronic midgap states

Zhugayevych

Lubchenko

2010

The Journal of Chemical Physics

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We propose a structural model that treats in a unified fashion both the atomic motions and electronic excitations in quenched melts of pnictide and chalcogenide semiconductors. In Part I (submitted to J. Chem. Phys.), we argued these quenched melts represent aperiodic ppσ-networks that are highly stable and, at the same time, structurally degenerate. These networks are characterized by a continuous range of coordination. Here we present a systematic way to classify these types of coordination in terms of discrete coordination defects in a parent structure defined on a simple cubic lattice. We identify the lowest energy coordination defects with the intrinsic midgap electronic states in semiconductor glasses, which were argued earlier to cause many of the unique optoelectronic anomalies in these materials. In addition, these coordination defects are mobile and correspond to the transition state configurations during the activated transport above the glass transition. The presence of the coordination defects may account for the puzzling discrepancy between the kinetic and thermodynamic fragility in chalcogenides. Finally, the proposed model recovers as limiting cases several popular types of bonding patterns proposed earlier, including: valence-alternation pairs, hypervalent configurations, and homopolar bonds in heteropolar compounds.

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Section: The Charge On the Coordination Defects And The Relation Tmentioning

confidence: 99%

Section: The Charge On the Coordination Defects And The Relation Tmentioning

confidence: 99%

Electronic structure and the glass transition in pnictide and chalcogenide semiconductor alloys. II. The intrinsic electronic midgap states

Zhugayevych

Lubchenko

2010

The Journal of Chemical Physics

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“…In the valence-alternation pair ͑VAP͒ model, these defects can be formed close to each other due to Coulomb attraction and are called intimate VAPs ͑IVAP͒. [32][33][34] VAP and IVAP are also known as random and nonrandom defects, respectively. 35 The intrinsic defects discussed above are considered the major contributors to the gap states in insulators.…”

Section: Introductionmentioning

confidence: 99%

Structural conditions that leads to photoluminescence emission in SrTiO3: An experimental and theoretical approach

Longo

Figueiredo

Lázaro

et al. 2008

Journal of Applied Physics

154

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• ͒ vacancies were identified in disordered SrTiO 3 powders prepared by the polymeric precursor method, based on experimental measurements by x-ray absorption near edge structure spectroscopy. The paramagnetic complex states of ͓TiO 5 · V O • ͔ and ͓SrO 11 · V O • ͔ with unpaired electrons were confirmed by electron paramagnetic resonance spectroscopy. The disordered powders showed strong photoluminescence at room temperature. Structural defects of disordered powders, in terms of band diagram, density of states, and electronic charges, were interpreted using high-level quantum mechanical calculations in the density functional framework. The four periodic models used here were consistent with the experimental data and explained the presence of photoluminescence.

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“…Ve suppose that ioiiising effect of electron irradiation results in excess density of the existing charge defects C ; and C ; according to the scheme: ...etastable states of cheloogen atom (C;)* exist only during the electronic irradietion. After the irradiation one of lone-pzir electrons snould better pass into the bonciinr state fonin; a C; defect center and "atomic shift" defect densities (iV) for the glass network elements (As2S3 and As2Se3) in table 1 are given. Bere atomic shift energy threshold is supposed to be Ed-25ev, and = 6 I (according to the (2) Thus it may be supposed that high-energy electrons irradiation of chalcogenide glasses gives rise to the excess valence-alternation pairs defects density, essentially affecting their electrica1,photoelectrical and optical properties.…”

Section: Sm Kirov Kaaakh S T a T E U N I V E R S I T Y 480091 Almentioning

confidence: 99%