Vacuum-evaporated ferroelectric films and heterostructures of vinylidene fluoride/trifluoroethylene copolymer
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ACE AND THIN FILMS Dedicated to the memory of A.V. Shubnikov
VacuumEvaporated Ferroelectric Films and Heterostructures of Vinylidene Fluoride/Trifluoroethylene Copolymer Yu. A. Draginda, S. G. Yudin, V. V. Lazarev, S. V. Yablonskii, and S. P. Palto Shubnikov Institute of Crystallography, Russian Academy of Sciences, Leninskii pr. 59, Moscow, 119933 Russia email: [email protected] Received March 2, 2011
Abstract—The potential of the vacuum method for preparing ferroelectric films and photonic heterostruc tures from organic materials is studied. Vacuumevaporated films of fluoropolymers and heterostructures on their basis are obtained and their ferroelectric and spectral properties are studied. In particular, homogeneous films of the wellknown piezoelectric polymer polyvinylidene fluoride and ferroelectric material vinylidene fluoride/trifluoroethylene copolymer (P(VDF/TFE)) are produced. Experimental studies of vacuumevap orated P(VDF/TFE) films confirmed their ferroelectric properties. The heterostructures composed of alter nating layers of P(VDF/TFE) copolymer molecules and azodye molecules are fabricated by vacuum evapo ration. Owing to the controlled layer thickness and a significant difference in the refractive indices of the P(VDF/TFE) copolymer and azodyes, these heterostructures exhibit properties of photonic crystals. This finding is confirmed by the occurrence of a photonic band in the absorption spectra of the heterostructures. DOI: 10.1134/S1063774512020071
INTRODUCTION Presently, both traditional and new technologies of ferroelectric polymer films are actively developed and improved. Wellknown techniques of this kind are centrifugation [1] and the Langmuir–Blodgett (LB) method [2]. The purpose of this study was to obtain ferroelectric polymeric films and heterostrictures based on these films by vacuum evaporation. The technology of ferroelectric polymeric films based on the LB method has been developed for a long time (since 1995), and several tens of studies on this subject have been published [2–6]. At the same time, there are few publications on the application of the vacuum evaporation of polyvinylidene fluoride (PVDF) poly mers and their copolymers [7–10]. The vacuum method is widely used to produce thin films of various inorganic materials (metals, semicon ductors, and dielectrics). In some cases it is also employed to evaporate organic substances. This method ensures the high quality of coatings, which determines its application in various hightech pro cesses. Since vacuum evaporation is related to the heating of substances to high temperatures, there are problems in the evaporation of organic materials, which can decompose and lose their functional prop erties above 300°С. Very special materials with low molecular weight were used in the aforementioned few works. The absence of studies in this field can be related to specific features of the vacuum thermal evaporation of ferroelectric polymers possessing high molecular weight. The vacuum technique of deposi tion offers wide poss
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