Revealing controllable nanowire transformation through cationic exchange for RRAM application

Area of Science:

• Materials Science
• Nanotechnology
• Solid-State Chemistry

Background:

• One-dimensional metal oxide nanostructures exhibit unique functional properties.
• Piezoelectric and photocatalytic materials, such as zinc oxide (ZnO) and titanium dioxide (TiO2), are of significant research interest.
• Developing advanced nanostructures for electronic applications like resistive random-access memory (RRAM) is crucial.

Purpose of the Study:

• To transform piezoelectric ZnO into photocatalytic TiO2 to form TiO2/ZnO axial heterostructure nanowires.
• To investigate the kinetic behavior and growth rate of TiO2 during the transformation.
• To design and analyze Pt/ZnO/TiO2/ZnO/Pt heterostructures for complementary resistive switching (CRS) applications to mitigate sneak-peak currents in RRAM.

Main Methods:

• Solid-to-solid cationic exchange reactions in a high-vacuum transmission electron microscope (TEM) (approx. 10⁻⁸ Torr).
• In situ TEM video analysis to measure the nanoscale growth rate of TiO2.
• Energy dispersive spectrometry (EDS) analysis to confirm the role of oxygen migration and TiO2 as a reservoir.

Main Results:

• Successfully synthesized TiO2/ZnO axial heterostructure nanowires with flat interfaces.
• Systematically analyzed the kinetic behavior and measured the nanoscale growth rate of TiO2.
• Demonstrated unique Pt/ZnO/TiO2/ZnO/Pt heterostructures exhibiting complementary resistive switching (CRS) characteristics.

Conclusions:

• The study provides a novel method for exploring material transformation mechanisms at the nanoscale.
• The synthesized ZnO/TiO2 heterostructures show potential for application in nanoscale crossbar array resistive random-access memory (RRAM).
• The observed resistive switching behavior is attributed to oxygen migration, with the TiO2 layer acting as an oxygen reservoir.