1. A nonvolatile memory device, comprising: at least one memory cell which comprises a diode and a metal oxide antifuse dielectric layer, the diode including a doped polycrystalline material that comprises a plurality of grains and a plurality of grain boundaries; and a first electrode and a second electrode electrically contacting the at least one memory cell; wherein in use, the diode acts as a read/write element of the memory cell by switching from a first stable resistivity state to a second stable resistivity state different from the first resistivity state in response to an applied bias such that at least some dopant atoms move from at least some of the plurality of grain boundaries to at least some of the plurality of grains; wherein the resistivity state of the diode corresponds to a memory state of the memory cell.