Ultrathin copolymer films of vinylidene fluoride and trifluoroethylene were deposited on Al-coated polyimide substrates, by the Langmuir-Blodgett method. A top Al electrode was evaporated onto the polymer film, to form an Al/polymer/Al structured infrared detector. The pyroelectric voltage response of the detector under various polarizing processes was characterized. The detector with only one transferred polymer layer exhibited a preferential polarization direction. This was considered to result from the self-polarization of the ultrathin polymer film. It was due to the preferred alignment of the dipoles on the Al substrates. This process can be applied for designing stable fast-response infrared detectors. (C) 2013 Elsevier B. V. All rights reserved.