Dependence of the Thermopower on Temperature and Crystal Direction in the Highly Anisotropic Organic Semiconductor TEA (TCNQ)<sub>2</sub><sup>1</sup>)

Parges, J. P.; Brau, A.

doi:10.1002/pssb.2220640131

Physica Status Solidi (b)

1974

DOI: 10.1002/pssb.2220640131

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Dependence of the Thermopower on Temperature and Crystal Direction in the Highly Anisotropic Organic Semiconductor TEA (TCNQ)₂¹)

J. P. Parges

A. Brau

Abstract: An investigation is made of the thermopower in the three available directions of crystals of TEA(TCNQ), and on a moulding pellet a t temperatures between 100 and 300 O K . The thermopower is found to be highly anisotropic with an anomalous sign for one direction; i t is negative in the directions of highest and lowest electrical conductivity but positive in the direction of intermediate conductivity.Nous presentons une etude du pouvoir thermoelectrique sur des cristaux de TEA(TCNQ),, suivant les trois directio… Show more

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Cited by 21 publications

References 9 publications

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Phase transition in the TCNQ complex salt formed from the cation (methyl-1-N-ethyl benzimidazolium)+?

Farges

Grassi

Brau

et al. 1979

Phys. Stat. Sol. (a)

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During cooling, the electrical conductivity measured in crystalline needles of (Me 1—NEt Bz)+ · (TCNQ) 2− undergoes a discontinuity from which it drops by a factor which can be as large as 300. The temperature at which the discontinuity occurs, of the order of 250 K, varies from needle to needle. If the needle is then re‐heated, its conductivity increases quite regularly and continuously, and after thermal cycling the starting value is practically recovered. The discontinuity is never observed with larger specimens of the same material, produced by re‐crystallisation. In this case it is then replaced by a steep but continuous conductivity anomaly.

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Phase transition in the TCNQ complex salt formed from the cation (methyl-1-N-ethyl benzimidazolium)+?

Farges

Grassi

Brau

et al. 1979

Phys. Stat. Sol. (a)

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Infrared Studies of TEA(TCNQ)2 Crystals Damaged by Electron Irradiation and Mechanical Treatment

Olejniczak

Graja

Brau

et al. 1994

Phys. Stat. Sol. (a)

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Infrared absorption and reflection spectra of the organic semiconductor TEA (TCNQ)2 nominally pure and damaged by electron irradiation and mechanical treatment are investigated. It is stated that in the salt damaged by mechanical treatment TEA (TCNQ)2 units are destroyed but not the individual TCNQ molecules. As opposed to that, the radiation‐damaged salt undergoes partial decomposition of the TCNQ molecules. This means that the mechanical and radiational damages of the TEA (TCNQ)2 salt are dissimilar from one another.

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Electrical Properties of (DEPE) (TCNQ)₄

Somoano

Hádek

Yen

et al. 1977

Physica Status Solidi (b)

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Conductivity measurements are performed on single crystals of two phases of (1,2-di(N-ethyl-4-pyridininm)ethylene2+) (7,7,8,8-tetracyanoquinodimethane):-, (DEPE) (TCNQ),. Conductivities are determined by four probe andMontgomery methods, and the highest values measured are those along the bo-axis for the monoclinic phase (I) crystals, = 50 (a cm)-l a t room temperature.The resistivities are in general exponentially activated (semiconducting behavior). Thermoelectric power measurements are performed along the b,-axis of phase I crystals and the thermopower tends to saturate a t high temperatures to -60 pV/K, characteristic of a quarter-filled correlated band. No evidence for the existence of a stable metallic state reported by Ashwell et al. was found. The preliminary crystal structures of both phases are discussed.An Einkristallen von zwei Phasen von (1,2-di(N-ethyl-4-pyridinium)ethylen2+) (7,7,8,8-tetracyanoquinodimethan)i-, (DEPE) (TCNQ), werden LeitfB;higkeitsmessungen durchgefuhrt. Die Leitfiihigkeiten werden mit der Vier-Sonden-Methode und der Methode von Montgomery bestimmt; die hochsten gemessenen Werte werden in Richtung der b,-Achse fur Kristalle der monoklinen Phase (I) zu = 50 (n cm)-l bei Zimmertemperatur bestimmt. Die Leitfiihigkeiten sind im allgemeinen exponentiell aktiviert (Halbleiterverhalten). Messungen der Thermokraft werden in Richtung der bo-Achse der Kristalle der Phase I durchgefiihrt, wobei die Thermospannung bei hohen Temperaturen einem Sattigungswert yon -60 pV/K zustrebt, was auf ein korreliertes, viertelgefulltes Band hinweist. Fur die Existenz eines stabilen metallischen Zustands. wie von Ashwell et al. berichtet, wird kein Hinweis gefunden. Die vorliiufigen Kristallstrukturen beider Phasen werden diskutiert.

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Dependence of the Thermopower on Temperature and Crystal Direction in the Highly Anisotropic Organic Semiconductor TEA (TCNQ)₂¹)

Cited by 21 publications

References 9 publications

Phase transition in the TCNQ complex salt formed from the cation (methyl-1-N-ethyl benzimidazolium)+?

Phase transition in the TCNQ complex salt formed from the cation (methyl-1-N-ethyl benzimidazolium)+?

Infrared Studies of TEA(TCNQ)2 Crystals Damaged by Electron Irradiation and Mechanical Treatment

Electrical Properties of (DEPE) (TCNQ)₄

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Dependence of the Thermopower on Temperature and Crystal Direction in the Highly Anisotropic Organic Semiconductor TEA (TCNQ)21)

Cited by 21 publications

References 9 publications

Phase transition in the TCNQ complex salt formed from the cation (methyl-1-N-ethyl benzimidazolium)+?

Phase transition in the TCNQ complex salt formed from the cation (methyl-1-N-ethyl benzimidazolium)+?

Infrared Studies of TEA(TCNQ)2 Crystals Damaged by Electron Irradiation and Mechanical Treatment

Electrical Properties of (DEPE) (TCNQ)4

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Product

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Dependence of the Thermopower on Temperature and Crystal Direction in the Highly Anisotropic Organic Semiconductor TEA (TCNQ)₂¹)

Electrical Properties of (DEPE) (TCNQ)₄