Epitaxial iron oxide nanocrystals with memory function grown on Si substrates

High-density Fe₃O_4-δ nanocrystals (NCs) were epitaxially grown on Si substrates by molecular beam epitaxy with epitaxial Ge NCs being used as nucleation sites. Scanning tunneling spectroscopy measurements showed that the surface bandgap of the as-grown Fe₃O_4-δ NCs was ~0.2 eV, consistent with that reported for Fe₃O_4-δ films. Conductive atomic force microscopy measurements of the NCs revealed hysteresis in the voltage- current curves, indicating bipolar resistive switching behavior. The measurement results established the superiority of the NCs to thin conventional polycrystalline Fe₃O_4-δ films/Si in terms of resistive switching characteristics. This demonstrated the possibility of developing resistance random access memory devices composed of ubiquitous Fe₃O_4-δ NC materials.