Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, Vol.284, 161-182, 1996
Thin-Films of BEDT-TTF and Bedo-TTF Radical-Cation Salts
In this communication we describe the fabrication and characterization of thin films of the radical cation salts alpha-, alpha(t)-(BEDT-TTF)(2)I-3 and (BEDO-TTF)(2.4)I-3. Thin films of these compounds were made by evaporation of the salts in high vacuum onto several substrates. They were characterized by X-ray diffraction, scanning electron microscopy, infrared absorption, Raman scattering, de-conductivity measurements and magnetically modulated microwave absorption. Depending on the temperature of the substrate and the evaporation rate, the films of alpha-(BEDT-TTF)(2)I-3 exhibit different degrees of microcrystallinity which under the right conditions can be strongly reduced to obtain relatively smooth, completely covering films. Additionally such films have a high degree of orientation with respect to the substrate plane. The conversion into films of the superconducting alpha(t)-phase is possible and the high orientation is maintained. Due to grain boundaries, the dc-conductivity is thermally activated, but the single grains are superconducting. The best results in the fabrication of smooth, completely covering films were obtained with (BEDO-TTF)(2.4)I-3 on NaCl single crystals. Here the orientation of the donor molecule with respect to the substrate plane is different from the one found in the (BEDT-TTF)(2)I-3 salts.
Keywords:DEPENDENT MICROWAVE-ABSORPTION;DIMENSIONAL ORGANIC METAL;SUPERCONDUCTORS;ALPHA-(BEDT-TTF)2I3;(BEDT-TTF)2CU(NCS)2;SPECTRA;1ST