Synthetic Metals, 60 (1993) 111-114 111 Conducting Langmuir-Blodgett films of hexadecyl-BEDT-TTF charge-transfer salts with inorganic compounds Tatiana S. Berzina and Vladimir I. Troitsky Zelenograd Research Institute of Physical Problems, 103460 Moscow (Russian Federation) Elisa Stussi, Marcello Mul6 and Danilo De Rossi Centro 'E. Piaggio; University o f Pisa, via Diotisalvi 2, 1-56122 Pisa (Italy) (Received December 11, 1992; in revised form March 18, 1993; accepted March 19, 1993) Abstract A method for forming conducting Langmuir-Blodgett films of charge-transfer salts based on the interaction between surfactant donor molecules spread at the air/water interface and inorganic compounds dissolved in water is proposed. Films of hexadecylbis(ethylenedithio)tetrathiafulvalene with small additions of surfactant acceptor molecules were deposited from water subphases containing FeCI3 or CuSO4. High quality films with conductivity of 2 ~-~ cm -1 were deposited at pH of 3.8 when Fe 3÷ ions at a concentration of 10 -4 M were used. In order to study the interaction of donor molecules with the compounds dissolved in water, electron probe analysis of the films was carried out. Variants of charge-transfer salt formation are discussed. Introduction Conducting Langmuir-Blodgett (LB) films [1] are promising components for the development of molecular electronic devices. Conducting layers can be introduced into assemblies of alternating LB monolayers [2] to provide electron transfer in horizontal planes. In ad- dition, discovery of field effect in conducting LB layers [3] makes conductivity modulation possible by means of an external electric field. Film conductance was proved to be destroyed by electron beam effect [4]. Therefore, high resolution patterns can be created using the electron beam lithography technique. Patterning of conducting paths can be obtained in principle with much higher spatial resolution by the effect of the current of the STM tip. In order to realize such possibilities, highly conductive, uniform and stable LB films with good sensitivity to the electron beam are necessary. In the pioneering work on conducting LB films of docosylpyridinium charge-transfer salt with TCNQ [1], precursor nonconducting films with a high degree of charge transfer between pyridinium and TCNQ groups were deposited. Then, stacks of TCNQ- anions were partially oxidized by iodine to obtain con- ductivity. The same procedure of iodine doping was used for preparing conducting films of one-component donor molecules [5]. In many cases some uncontrolled doping took place in the process of deposition and conductance without any treatment was observed. Two- component LB films consisting of alternating surfactant donor and acceptor monolayers [6] were used in another attempt. LB films consisting of mixed monolayers of such compounds [7] were also formed to provide charge transfer between donor and acceptor molecules. Electrically conducting polypyrrole LB films were deposited from the surface of a subphase containing ferric chloride [8, 9]. This inorganic compound was used to polymerize and oxidize the mixture of pyrrole monomer and surface active pyrrole derivative at the air/water interface, giving rise to electrical conductance. The best value of conductivity obtained was equal to 0.1 l'1-1 cIr1-1. In the present work we used a procedure for forming LB films of charge-transfer salts based on the interaction between surfactant donor molecules spread at the air/ water interface and inorganic compounds dissolved in water. Conducting films of hexadecylbis(ethylenedi- thio)tetrathiafulvalene (C16-BEDT-TrF) with small ad- ditions of surfactant acceptor molecules were deposited from water subphases containing FeC13, or CuSO4 at different concentrations and pH values. Quality of the deposited films was verified by optical microscopy and conductivity was measured. Electron probe analysis of the films deposited onto ultrathin collodion substrates was carried out in order to study the interaction of donor molecules with the compounds dissolved in water. 0379-6779/93/$6.00 © 1993- Elsevier Sequoia. All rights reserved