Strain-induced superconductor/insulator transition and field effect in a thin single crystal of molecular conductor

Abstract

The strain in an organic field-effect channel was controlled using a pressure-sensitive organic superconductor -͑BEDT-TTF͒ 2 Cu͓N͑CN͒ 2 ͔Br ͓BEDT-TTF= bis͑ethylenedithio͒tetrathia-fulvalene͔. The difference in thermal properties between the channel and the substrate induced strain with cooling, resulting in a phase transition. An unshrinkable SiO 2 / Si substrate was used to strain the subject material to the insulating state at low temperature, whereas a shrinkable polymer-based substrate allowed it to be a superconductor. The strain-induced insulating phase on SiO 2 / Si is at the vicinity of the phase boundary with the superconducting phase, actualizing field-effect transistor behavior.

Gate-Induced Thermally Stimulated Current on the Ferroelectric-like Dielectric Properties of (BEDT-TTF)(TCNQ) Crystalline Field Effect Transistor

“…Thermal expansion coefficient of Si wafer is much smaller than that of the organic materials. Therefore, if there is no slippage at the interface, the in-plane (b-c plane) lattice parameter of the organic crystal at around the interface of the Si wafer is effectively expanded with decreasing temperature compared to its thermal expansion in free crystal [24,25]. In fact, in our preliminary result, distance of (0kl) planes are expanded compared to the free (0kl) plane distance (to be published elsewhere).…”

Asymmetric Phase Transitions Observed at the Interface of a Field‐Effect Transistor Based on an Organic Mott Insulator

“…If V G was applied, the device showed simple ambipolar characteristics (Figure 2, a) at temperatures higher than 11 K. This is the first example of a clear ambipolar Mott FET made from κ-Br, and we have only observed n-type or ptype behavior before. [2,5] This observation of an ambipolar field effect originates under the clean conditions used in the device fabrication process, under which a lower midgap state density is achieved. The device mobility (μ) for the ntype region, which was determined by the formula μ = 1/C(dσ/dV G ), well exceeded that for the p-type region.…”

“…[2,5] In those experiments, the κ-Br crystals were expanded or shrunk as the device was cooled down, because of the mismatch in thermal expansion coefficients between κ-Br and the substrates. However, the extent of the strain was evaluated only by indirect methods such as resistivity and magnetization measurements.…”

Organic field‐effect transistors fabricated by solution process using TMTSF‐TCNQ complex crystals grown at various temperatures

“…In Fig. 3, the diffraction peak of the planar crystals denoted as a 11 , positioned at 2θ = 7.29°, is assigned to the fundamental one from planes whose lattice spacing is calculated to be 1.21 nm. The other peaks at 14.61° denoted as a 12 Fig.…”