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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.

No MeSH data available.


XRD patterns (a) and Raman spectra (b) of (1) as-grown film, (2) pure phase orthorhombic V2O5 (PDF no-750457) obtained after oxidation and (3) monoclinic VO2 M1 phase (PDF no-03-065-2358) obtained upon V2O5 annealing under vacuum. The average crystallite size of V2O5 and VO2 is 22 nm and 27 nm respectively.
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f1: XRD patterns (a) and Raman spectra (b) of (1) as-grown film, (2) pure phase orthorhombic V2O5 (PDF no-750457) obtained after oxidation and (3) monoclinic VO2 M1 phase (PDF no-03-065-2358) obtained upon V2O5 annealing under vacuum. The average crystallite size of V2O5 and VO2 is 22 nm and 27 nm respectively.

Mentions: The as-grown films using cyclohexane as a liquid carrier (step 1) are XRD-amorphous (Fig. 1a), which contrasts with the crystalline VO2 films obtained with ethanol at this temperature range23. On the other hand, cyclohexane is thermally more stable than ethanol at 600 °C31. For instance, the pyrolysis of ethanol in the temperature range 576–624 °C produces essentially methane, hydrogen and oxygen containing compounds as acetaldehyde and carbon monoxide32. In contrast to cyclohexane, ethanol is able to participate into the deposition chemistry as a potential source of oxygen. It is worth mentioning that the as-grown films represent the VO2 characteristic Raman signature (Fig. 1b) but do not feature any obvious sudden change of electrical resistivity upon heating. It is therefore necessary to apply post-deposition treatments to improve the crystallinity of VO2 films and decrease the density of the grain boundaries.


Electrical Switching in Semiconductor-Metal Self-Assembled VO 2 Disordered Metamaterial Coatings
XRD patterns (a) and Raman spectra (b) of (1) as-grown film, (2) pure phase orthorhombic V2O5 (PDF no-750457) obtained after oxidation and (3) monoclinic VO2 M1 phase (PDF no-03-065-2358) obtained upon V2O5 annealing under vacuum. The average crystallite size of V2O5 and VO2 is 22 nm and 27 nm respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: XRD patterns (a) and Raman spectra (b) of (1) as-grown film, (2) pure phase orthorhombic V2O5 (PDF no-750457) obtained after oxidation and (3) monoclinic VO2 M1 phase (PDF no-03-065-2358) obtained upon V2O5 annealing under vacuum. The average crystallite size of V2O5 and VO2 is 22 nm and 27 nm respectively.
Mentions: The as-grown films using cyclohexane as a liquid carrier (step 1) are XRD-amorphous (Fig. 1a), which contrasts with the crystalline VO2 films obtained with ethanol at this temperature range23. On the other hand, cyclohexane is thermally more stable than ethanol at 600 °C31. For instance, the pyrolysis of ethanol in the temperature range 576–624 °C produces essentially methane, hydrogen and oxygen containing compounds as acetaldehyde and carbon monoxide32. In contrast to cyclohexane, ethanol is able to participate into the deposition chemistry as a potential source of oxygen. It is worth mentioning that the as-grown films represent the VO2 characteristic Raman signature (Fig. 1b) but do not feature any obvious sudden change of electrical resistivity upon heating. It is therefore necessary to apply post-deposition treatments to improve the crystallinity of VO2 films and decrease the density of the grain boundaries.

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.