Space charge polarization-induced symmetrical negative resistive switching in individual p-type GeSe2:Bi superstructure nanobelts for non-volatile memory

Abstract

Layered GeSe₂ nanobelts doped with Bi have been synthesized by thermal reduction of Bi₂Se₃ nanopowder using germanium (Ge). The nanobelts prepared showed excellent p-type conductivity, with hole mobility as high as 690 cm² V⁻¹ s⁻¹. The introduction of Bi leads to the formation of a commensurate superstructure, and induces the growth of nanobelts along the [010] direction. Two-terminal devices, based on individual GeSe₂:Bi nanobelts with Ag electrodes, showed symmetrical resistive switching (RS) behavior accompanied by negative differential resistance. A space charge polarization model has been proposed. For the doping of Bi, the ordered superstructure defects and variable valences create trap centers, in which charges can effectively be captured and stored to generate polarization effects under a relatively large applied electric field. Additionally, the relatively large negative RS window can further be utilized as a non-volatile resistance random access memory (RRAM). The superior stability, reversibility, non-destructive readout and good cycling performance of the nanodevices demonstrated that Bi-doped GeSe₂ nanobelts have considerable potential in next-generation non-volatile memory applications.