Low‐Field Negative‐Resistance Effect in a Charge‐Ordered State of Thiazyl‐Radical Crystals

Abstract

Resistance is useful: A thiazyl‐radical salt, [NT]3[GaCl4] (see structural diagram), exhibits negative resistance (see graph) in a charge‐ordered state of the square columnar network of NT molecules. As the negative‐resistance effect is observed at low electrical fields and high temperatures (290 K), it is potentially attractive for applications such as electrical devices.

A Mechanism of DC-AC Conversion in the Organic Thyristor

“…This dc-ac conversion (inverter effect) indicates that the organic thyristor can be used for an oscillating circuit like a conventional thyristor device. After this discovery, the nonlinear conduction in organic conductors has received a renewed attention [5,6,7], although many of organic materials were recognized for non-ohmic conductors long before. [8,9,10,11,12,13] The current oscillation has been also searched and discovered in various strongly correlated systems [14,15].…”

Electron-Transfer Processes in Highly-Correlated Electron Systems of Thiazyl Radicals

“…In this section, we describe the crystal structure of these 3:1 salts, which exhibit a characteristic charge-ordering and nonlinear transport probably due to a partial melting of this ordering. Figure 4 shows the crystal structure of (NT) 3 [GaCl 4 ] at 173 K, 55,56 which includes crystallographically independent 2D layers of NT, Layers A and B (Figure 4a), though their structures are nearly the same. Each layer is formed by a 2D square network of NT with short S£N contacts, in which the molecular planes of NT are parallel to the layer.…”

“…By using the relation between the average SN bond distance l SN and the charge μ on NT, which is obtained by the analyses of the neutral NT molecule, 53 the NT + cation in (NT)Cl, 54 and a mixed-valence state (NT)(TCNQ), 55 the values of μ for the four crystallographically-independent NT molecules in (NT) 3 [GaCl 4 ] can be estimated as (i) 0.8, (ii) 0, (iii) 0.5, and (iv) 0.1. 55,56 The crystal structure of (NT) 3 [GaCl 4 ] can be characterized by a significant charge ordering. Such a 3D charge alternation is gaining much attention as a characteristic insulating state induced by intermolecular Coulomb repulsions in strongly correlated systems.…”

Molecular-based light-activated thyristor

“…14 In the current-voltage ͑I-V͒ characteristics, field-induced switching effects have been discovered recently in several molecular conductors. 5,[15][16][17] The fieldinduced switching effect can, in general, be attributed to the differential-negative-resistance ͑DNR͒ effect in the I-V characteristic curve of materials. 18,19 The structural change upon the switching has been investigated for a few molecular conductors using x-ray crystallographic methods.…”

“…These values are rather small in comparison with those of other organic materials that show the field-induced DNR effect. 15 This feature may be technically advantageous since the pulsed voltage with a height lower than 10 V can induce the DNR effect, as shown in Figs. 1 and 2, and this range of …”