  Ferroelectricity in van der Waals (vdW) layered material has attracted a
great deal of interest recently. CuInP$_2$S$_6$ (CIPS), the only vdW layered
material whose ferroelectricity in the bulk was demonstrated by direct
polarization measurements, was shown to remain ferroelectric down to a
thickness of a few nanometers. However, its ferroelectric properties have just
started to be explored in the context of potential device applications. We
report here the preparation and measurements of metal-ferroelectric
semiconductor-metal heterostructures using nanosheets of CIPS obtained by
mechanical exfoliation. Four bias voltage and polarization dependent resistive
states were observed in the current-voltage characteristics, which we attribute
to the formation of ferroelectric Schottky diode, along with switching
behavior.
