Ferroelectricity of a hemicyanine dye in ultrathin organized molecular films: hysteresis and pyroelectric effects

Pyroelectricity of the optical nonlinear hemicyanine dye in organized molecular films has been demonstrated by using the electric polarization and second harmonic generation measurements. The typical hysteresis loop of the samples confirmed existence of the remnant polarization of hemicyanine molecules which is 600 μC m−2. The pyroelectric coefficient of hemicyanine was found to be 12 μC m−2 K−1 at room temperature and enhanced with increasing temperature monotonically which was well explained by using a molecular dipole reorientation model.