Charge-transfer mechanism and electronic properties of a new metallic Langumuir-Blodgett films

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1. The present investigators have made a success to make a new metallic Langmuir-Blodgett films of BEDO-TTF and stearic acid showing the dc conductivity 100 S/cm at room temperature. The present molecular system forms bi-layer organization with upper stearic acid and lower BEDO-TTF layers leading the formation of charge-transfer complex as (BO)2ィイD1+ィエD1(RCOO-H..OOCR)ィイD1-1ィエD1. Consequently, it has become unnecessary neither to attach a long di-hydrocarbon chain to the electroactive molecule nor to put additional fatty acid to increase the stability.2. The LB films of BEDO-TTF and stearic acid with 1:1 mixing exhibit the logarithmic increase of the dc resistance with decreasing temperature below 120 K. As a result of the study of transverse magnetoresistance down to 1.8 K we found out the negative magnetoresistance, for which we interpreted the characteristics of the existence of weakly localized two-dimensional (2D) electronic system. A theory developed by Hikami et al. was applied to the quantitative fit to obtain several microscopic parameters govern the present single carrier quantum interference phenomena. We got the quantitative values of sheet resistance and Thouless length as a function of temperature which gives an evidence of the 2D electronic system with weal localization under the coherent regime.3. The present LB films are not superconducting but classified as a dirty metal as in graphite GIC compounds and/or semiconductor superlattice. The suppression of the localization is crucial to survey of low-temperature electronic ground state such as superconductivity with zero resistance in a macroscopic scale.