Electrical Properties of PVDF/InSe and P (VDF·TFE)/InSe Junction Systems

Indium monoselenide (InSe) is a layer structure semiconductor, with interlayer bonding by van der Waals' force, and because of the small number of dangling bonds at layer cleavage planes. InSe is well suited to forming junction systems with different substances. Polyvinylidene-fluoride (PVDF) and vinylidene fluoride-tetrafluoroethylene copolymer [P(VDF·TFE)=β PVDF type], on the other hand, readily form ferroelectric thin films. The PVDF polarized in to flying clusters in the vacuum vapor deposition atmosphere, so that the probability of sticking differs depending on the kind of substrate. InSe single crystals prepared by the synthesis solute diffusion (SSD) method had n-type electric conduction, electric conductivity σ of 3.1×10-1S/cm, Hall mobillity μ of 200cm2/v·s, and a band gap of 1.1eV at room temperature. Thin films of PVDF were formed by vacuum vapor deposition on the InSe cleavage layer planes. The equivalent circuit of the PVDF/InSe junction system obtained was a parallel circuit consisting of a resistance and a condenser, and differences were observed in the capacity-voltage curve for the junction system due to polarization, according to whether the PVDF was α or β. The change in this curve becomes greater as the dielectric constant of the PVDF increases. In the PVDF/InSe junction system, a variation of the space-charge density were dependent on polarization voltage and molecule structure of the PVDF.