Evaluation of Electroactive LB Films as

3 EVALUATION OF ELECTROACTIVE LB FILMS AS ACTIVE COMPONENTS OF THIN FILM DEVICES 

The first demonstration of the use of a conducting poljmo based LB film as the active element of an electronic device was made by Stubb s group in Hnland [38]. In diis woik, it was shown that mixed LB films of poly(3-hexylthiophene) and arachidic add (60 mole % P3HT) could be fabricated into wori g field effect transistors Q ETs) in which the undoped polymer served as the active semiconductor. Devices with film thicknesses ranging from a single monolayer (37A) to 35 monolayas (1295 A) were fabricated into 

FETs having a channel width and length of 8 cm and 5 pm respectively. Using this approach, it was possible to observe field-effects in the devices fabricated from a sin e monolayer. The mobilities and conductivities were found to decrease as the thickness of the LB film decreased. The mobilities of the LB film based devices (about 7 x 10 cm A s for a thick film) were also found to be lower than that reported for a spin coated film of pure P3HT (lx 10 cm /Vs) and this was attributed to the presence of die surface active molecules. 

In the undoped state, it can be seen that mobility and conductivity increase slightly with increasing film thickness. The magnitu of this effect is smaller than that observed in the LB film based FETs fabricated with P3HT and arachidic acid suggesting that the charge 

Although still in an early stage of development, research on the fabrication and evaluation of LB multilayer thin films of conducting polymers has already proven that this approach can be used to control the molecular and supomolecular organizations of these extremely interesting matoials. As this area matures, it should be possible to fabricate a wide variety of complex molecular assemblies with electrical and optical propmies tiiat can be tailored at the molecular and supermolecular level. It is also anticipated that significantly more 

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