Nanoionic memristive phenomena in metal oxides: the valence change mechanism

Moisture Effect on the Threshold Switching of TOPO-Stabilized Sub-10 nm HfO2 Nanocrystals in Nanoscale Devices

“…By further decreasing voltage, we find the same hysteresis as described for positive applied voltages. This symmetry can be attributed to the symmetric device design Au/TOPO-HfO 2 NC/Au . It results from average identical interface interactions at both TOPO-HfO 2 NC/Au interfaces, as described, for example, for a recently reported Pt/TiO 2 /Pt nanobelt device .…”

“…The presence of interstitial cations (Hf or other cations through doping) or oxygen vacancies, V o •• , is one requirement for the formation of conductive filaments in HfO 2 materials and thus for the enabling of resistive switching. , Here, we employ crystalline HfO 2 NC, which are not expected to have a high defect density, as an insulating material between two metal electrodes with a high work function. At these noble metal electrodes, no oxygen exchange reaction is possible, leading essentially to an electron transport through the Au/TOPO-HfO 2 NC interface.…”

“…At these noble metal electrodes, no oxygen exchange reaction is possible, leading essentially to an electron transport through the Au/TOPO-HfO 2 NC interface. For this scenario, the main contribution to the current transport is based on an interface-limited, trap-assisted tunneling. , Most likely, in the NC­(dry) film, the surface of the monoclinic HfO 2 NC or the TOPO molecules may serve as charge carrier traps.…”

“…1,9−11 It is known that in HfO 2 ReRAM, the resistive hysteresis is generated by an oxygen vacancy drift and linked redox reactions due to an applied electric field. 9,12,13 A well-established ligand for the synthesis of NC is tri-noctylphosphine oxide (TOPO), which enables the formation of nanocrystallites with narrow size distribution and a high colloidal stability in organic solvents. TOPO itself is soluble in a variety of common solvents, such as toluene, hexane, or methanol.…”

“…HfO 2 is used in metal–oxide semiconductor field-effect transistors, ferroelectric field-effect transistors, highly scaled dynamic random access memories, and resistive random access memories (ReRAM). Especially, its proven CMOS compatibility and full scalability make it an advantageous material for future nanoelectronic devices. ,− It is known that in HfO 2 ReRAM, the resistive hysteresis is generated by an oxygen vacancy drift and linked redox reactions due to an applied electric field. ,, …”