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Electrical Switching in Semiconductor-Metal Self-Assembled VO 2 Disordered Metamaterial Coatings

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ABSTRACT

As a strongly correlated metal oxide, VO2 inspires several highly technological applications. The challenging reliable wafer-scale synthesis of high quality polycrystalline VO2 coatings is demonstrated on 4” Si taking advantage of the oxidative sintering of chemically vapor deposited VO2 films. This approach results in films with a semiconductor-metal transition (SMT) quality approaching that of the epitaxial counterpart. SMT occurs with an abrupt electrical resistivity change exceeding three orders of magnitude with a narrow hysteresis width. Spatially resolved infrared and Raman analyses evidence the self-assembly of VO2 disordered metamaterial, compresing monoclinic (M1 and M2) and rutile (R) domains, at the transition temperature region. The M2 mediation of the M1-R transition is spatially confined and related to the localized strain-stabilization of the M2 phase. The presence of the M2 phase is supposed to play a role as a minor semiconducting phase far above the SMT temperature. In terms of application, we show that the VO2 disordered self-assembly of M and R phases is highly stable and can be thermally triggered with high precision using short heating or cooling pulses with adjusted strengths. Such a control enables an accurate and tunable thermal control of the electrical switching.

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(a) Thermal imaging of VO2 film near the phase transition showing the formation of small metallic clusters as purple spots that grow in size with temperature. (b) The fraction of monoclinic and rutile phases calculated from the change of color in the thermal images during the cooling stage.
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f5: (a) Thermal imaging of VO2 film near the phase transition showing the formation of small metallic clusters as purple spots that grow in size with temperature. (b) The fraction of monoclinic and rutile phases calculated from the change of color in the thermal images during the cooling stage.

Mentions: NIR images in Fig. 5a display the evolution of the rutile metallic domains (low emissivity) with increasing temperature across the transition. These domains grow rapidly in size with a small increase in temperature until coalescence. Similar to temperature dependent XRD patterns and NIR reflection behavior, we notice a difference of ΔT = 1–2 K between the heating and cooling stages, which confirms the small width of the hysteresis curve. The fraction and distribution of the metallic domains at 67–67.5 °C during the heating stage are equivalent to these at 66–66.5 °C in the cooling stage.


Electrical Switching in Semiconductor-Metal Self-Assembled VO 2 Disordered Metamaterial Coatings
(a) Thermal imaging of VO2 film near the phase transition showing the formation of small metallic clusters as purple spots that grow in size with temperature. (b) The fraction of monoclinic and rutile phases calculated from the change of color in the thermal images during the cooling stage.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121613&req=5

f5: (a) Thermal imaging of VO2 film near the phase transition showing the formation of small metallic clusters as purple spots that grow in size with temperature. (b) The fraction of monoclinic and rutile phases calculated from the change of color in the thermal images during the cooling stage.
Mentions: NIR images in Fig. 5a display the evolution of the rutile metallic domains (low emissivity) with increasing temperature across the transition. These domains grow rapidly in size with a small increase in temperature until coalescence. Similar to temperature dependent XRD patterns and NIR reflection behavior, we notice a difference of ΔT = 1–2 K between the heating and cooling stages, which confirms the small width of the hysteresis curve. The fraction and distribution of the metallic domains at 67–67.5 °C during the heating stage are equivalent to these at 66–66.5 °C in the cooling stage.

View Article: PubMed Central - PubMed

ABSTRACT

As a strongly correlated metal oxide, VO2 inspires several highly technological applications. The challenging reliable wafer-scale synthesis of high quality polycrystalline VO2 coatings is demonstrated on 4” Si taking advantage of the oxidative sintering of chemically vapor deposited VO2 films. This approach results in films with a semiconductor-metal transition (SMT) quality approaching that of the epitaxial counterpart. SMT occurs with an abrupt electrical resistivity change exceeding three orders of magnitude with a narrow hysteresis width. Spatially resolved infrared and Raman analyses evidence the self-assembly of VO2 disordered metamaterial, compresing monoclinic (M1 and M2) and rutile (R) domains, at the transition temperature region. The M2 mediation of the M1-R transition is spatially confined and related to the localized strain-stabilization of the M2 phase. The presence of the M2 phase is supposed to play a role as a minor semiconducting phase far above the SMT temperature. In terms of application, we show that the VO2 disordered self-assembly of M and R phases is highly stable and can be thermally triggered with high precision using short heating or cooling pulses with adjusted strengths. Such a control enables an accurate and tunable thermal control of the electrical switching.

No MeSH data available.


Related in: MedlinePlus