What is it about?

Modulation of insulator metal transition (IMT) of vanadium dioxide (VO2) films with crystallization of capping chalcogenide GST layer was demonstrated. The chalcogenide germanium- antimony-telluride (Ge2Sb2Te5: GST) shows large volume reduction of 6.8% with its phase change from amorphous to crystal. Thus, crystallization of GST film on VO2 films results in lattice length change between V-V atoms of the VO2 film, which is parallel to the Al2O3 (001) single crystalline substrate. We also introduced VO2 film grown on TiO2 (001) substrate, where direction of V-V chains is perpendicular to the TiO2 (001) substrate, hence crystallization of GST resulted in counter shift of IMT of VO2 films. The obtained results open a way to realize large resistance change of IMT under constant temperature by controlling GST phases.

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Why is it important?

Vanadium dioxide is known as phase transition compound which shows insulator metal transition (IMT) with large resistance change over three orders of magnitudes at around 68 °C. However, this IMT is volatile characteristic, where resistance shows reversible change with temperature change. This study focuses on shift of IMT temperature by the strong compression by capped GST layer on the VO2 films grown on single crystalline substrates. Observed shift of the IMT by crystallization of GST layer suggests possibility of nonvolatile resistance change with the change of GST between amorphous and crystalline states.


The results obtained in this study suggested that the large resistance change of phase transition VO2 film can be controlled by the crystallization and amorphization of capping GST layer. If we succeed in amorphization of GST, then we will see nonvolatile control of resistance value of VO2 film which opens a way to new electrical memory device.

Kunio Okimura
Tokai University

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This page is a summary of: Modulation of insulator metal transition of VO₂ films grown on Al2O3 (001) and TiO2 (001) substrates by the crystallization of capping Ge2Sb2Te5 layer, Journal of Applied Physics, December 2023, American Institute of Physics,
DOI: 10.1063/5.0176810.
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