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

Abstract

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.

Local and Spatial Disorder in β‘ ‘-(ET)2SF5RSO3 Solid Solutions (R = CH2CF2, CHF, CHFCF2)

“…Disorder is a well-known rival of superconductivity, as found for a variety of materials in a number of different forms. Examples include crystallographic disorder, solvent disorder, radiation-induced disorder, localization disorder, thermal disorder, cooling-rateinduced disorder, structural disorder due to composition changes, orientational disorder by chemical design, and magnetic disorder, [1][2][3][4][5][6][7][8][9][10][11][12][13] to name but a few. The effect of various types of disorder on molecular superconductors has been an area of particular interest ever since superconductivity was observed in these systems.…”

“…The effect of various types of disorder on molecular superconductors has been an area of particular interest ever since superconductivity was observed in these systems. 3,7,[14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] For instance, the superconducting state of the first ambient pressure molecular superconductor, (TMTSF) 2 -ClO 4 , where TMTSF is tetramethyltetraselenalfulvalene, is suppressed by anion disorder created by thermal quenching, defects induced by doping with small amounts of TMTTF, and to a lesser extent by radiation damage to the conducting chains. [14][15][16] More recently, the superconducting transition temperature of the intriguing κ-(ET) 2 Cu + (2-x-y) Cu 2+ x (CN) (3-2y) [N(CN) 2 ] y system, where ET refers to BEDT-TTF or bis(ethylenedithio)tetrathiafulvalene), can be tuned between 3.2 and 10 K by adjusting the x and y parameters.…”

“…The effects of disorder are evident in key physical properties such as the lowering of a superconducting transition temperature, T c , and the broadening of vibrational modes in an infrared spectrum. 3,32 Among the organic solids, the β′′-(ET) 2 SF 5 RSO 3 family of materials has attracted attention because of the tunable nature of the counterion and the different ground states that are observed in this system. [33][34][35][36][37][38] In the β′′ system, R ) CH 2 CF 2 , CHF, and CHFCF 2 yield superconducting (T c ∼ 5.2 K), metallic, and metalinsulator materials, respectively.…”

“…Examples include crystallographic disorder, solvent disorder, radiation-induced disorder, localization disorder, thermal disorder, cooling-rate-induced disorder, structural disorder due to composition changes, orientational disorder by chemical design, and magnetic disorder, − to name but a few. The effect of various types of disorder on molecular superconductors has been an area of particular interest ever since superconductivity was observed in these systems. ,,− For instance, the superconducting state of the first ambient pressure molecular superconductor, (TMTSF) 2 ClO 4 , where TMTSF is tetramethyltetraselenalfulvalene, is suppressed by anion disorder created by thermal quenching, defects induced by doping with small amounts of TMTTF, and to a lesser extent by radiation damage to the conducting chains. − More recently, the superconducting transition temperature of the intriguing κ-(ET) 2 Cu + (2 - x - y ) Cu 2+ x (CN) (3 - 2 y ) [N(CN) 2 ] y system, where ET refers to BEDT-TTF or bis(ethylenedithio)tetrathiafulvalene), can be tuned between 3.2 and 10 K by adjusting the x and y parameters. , Various types of imperfections cause disorder over different length scales. Radiation-induced disorder creates large length-scale damage, crystallographic disorder and alloying create medium-length irregularities, and solvent and orientational disorder result in localized, molecular-scale disorder.…”

“…Radiation-induced disorder creates large length-scale damage, crystallographic disorder and alloying create medium-length irregularities, and solvent and orientational disorder result in localized, molecular-scale disorder. The effects of disorder are evident in key physical properties such as the lowering of a superconducting transition temperature, T c , and the broadening of vibrational modes in an infrared spectrum. , …”