Fabrication And Properties Studies Of The Organic Ferroelectric Thin Films

Ferroelectrics are electroactive materials which have been widely used in thermal imaging, data storage, mechanical actuation, energy harvesting and so on, since their spontaneous polarizations can be controlled by temperature, electric field and mechanical stress, as well as magnetic field. Presently, applications of ferroelectrics have been dominated by inorganic perovskite-type materials, such as lead zirconate titanate (PZT) and barium titanate (BTO). The drawbacks in spontaneous polarization, transition temperature, and thermal stability limit the applications of molecular ferroelectrics. However, molecular ferroelectrics have some advantages including light weight, mechanical flexibility, easily designing, and environmentally friendly synthesizing compared with inorganic ferroelectrics, especially those containing toxic heavy metals like Lead.Ferroelectric thin films may exhibit different properties from that of crystals. Diisopropylammonium Bromine (DIPAB) and Diisopropylammonium Perchlorate (DIPAP) are two newly discovered molecular ferroelectrics, especially DIPAP displays an above-room-temperature ferroelectric to paraelectric transition temperature (Tc=338 K).We use the convenient and inexpensive spin-coating method to make a smooth thin film with single orientation at (101) plane on Si (001) substrates. The roughness of DIPAP thin film is less than 4 nm in a range of 10 μm, which fully meets the requirements of practical applications. The dielectric properties show that the thin film of DIPAP is a typical ferroelectric relaxor, which is completely different from the crystal. The ferrolelectricity of DIPAP thin films are confirmed by PFM, pyroelectricity, and hysteresis loop, which show a very small coercive electric filed. It is very important for the applications of ferroelectric thin films.