  We report the fabrication and the electrical characterization of back-gated
field effect transistors with black phosphorus channel. We show that the
hysteresis of the transfer characteristic, due to intrinsic defects, can be
exploited to realize non-volatile memories. We demonstrate that gate voltage
pulses allow to trap and store charge inside the defect states, which enable
memory devices with endurance over 200 cycles and retention longer than 30
minutes. We show that the use of a protective poly (methyl methacrylate) layer,
positioned on top of the black phosphorus channel, does not affect the
electrical properties of the device but avoids the degradation caused by the
exposure to air.
