Structure and properties of the highly conductive Langmuir–Blodgett films based on ditetradecyldimethylammonium-Au(dmit) 2 salt

•The structure and properties of the Au(dmit)2 LB film have been studied.•The Au(dmit)2 dimers are partially oxidized even in the as-deposited film.•The number of the oxidized Au(dmit)2 dimers increases with the electro-oxidation.•Some IR-inactive modes are observed by electron-molecular vibration coupling.•The electro-oxidized LB film consists of insulating and conducting domains.