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

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.


(a) Raman surface mapping of the M1, M2, M1 + M2 and R phases as measured at 67.5 °C (each dot correspond to 1 × 1 μm2 analysis area) and (b) Raman spectra corresponding to the color-coded used in the mapping.
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f8: (a) Raman surface mapping of the M1, M2, M1 + M2 and R phases as measured at 67.5 °C (each dot correspond to 1 × 1 μm2 analysis area) and (b) Raman spectra corresponding to the color-coded used in the mapping.

Mentions: Therefore, Raman mapping was performed at 67.5 °C for both wavenumbers (M2:650 cm−1 and M1:620 cm−1), Fig. 8a, to spatially localize the distribution of M1, M2 and R phases. This enables the spatial mapping of polycrystalline VO2 surface to visualize the random distribution of different phases. Each pixel corresponds to a 1 × 1 μm2 analysis area. The red dots in Fig. 8a represent M1 phase, whereas the green and yellow dots represent M2 and M1 + M2 domains respectively. The black background illustrates the presence of the R phase of VO2. The spectra of the aforementioned colored points in the Raman map are displayed in Fig. 8b. Hence, Raman mapping evidences clearly the self-assembly of a disordered M1-M2-R metamaterial at the transition temperature. It is worth mentioning that the presence of M2 phase was not evidenced above 70 °C, which is likely due to the excessive dominance of the metallic rutile phase. The entire SEM micrograph, Fig. 2, depicts a certain number of crystals and grain boundaries in an area that nearly corresponds to 1 × 1 μm2, which is the size of a single pixel in Fig. 8. This means that every single pixel (Fig. 8) contains a large number of grains/crystals and grain boundaries. Therefore, correlating the detection of M2 phase with morphological features such as grain boundary seems unlikely.


Electrical Switching in Semiconductor-Metal Self-Assembled VO 2 Disordered Metamaterial Coatings
(a) Raman surface mapping of the M1, M2, M1 + M2 and R phases as measured at 67.5 °C (each dot correspond to 1 × 1 μm2 analysis area) and (b) Raman spectra corresponding to the color-coded used in the mapping.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f8: (a) Raman surface mapping of the M1, M2, M1 + M2 and R phases as measured at 67.5 °C (each dot correspond to 1 × 1 μm2 analysis area) and (b) Raman spectra corresponding to the color-coded used in the mapping.
Mentions: Therefore, Raman mapping was performed at 67.5 °C for both wavenumbers (M2:650 cm−1 and M1:620 cm−1), Fig. 8a, to spatially localize the distribution of M1, M2 and R phases. This enables the spatial mapping of polycrystalline VO2 surface to visualize the random distribution of different phases. Each pixel corresponds to a 1 × 1 μm2 analysis area. The red dots in Fig. 8a represent M1 phase, whereas the green and yellow dots represent M2 and M1 + M2 domains respectively. The black background illustrates the presence of the R phase of VO2. The spectra of the aforementioned colored points in the Raman map are displayed in Fig. 8b. Hence, Raman mapping evidences clearly the self-assembly of a disordered M1-M2-R metamaterial at the transition temperature. It is worth mentioning that the presence of M2 phase was not evidenced above 70 °C, which is likely due to the excessive dominance of the metallic rutile phase. The entire SEM micrograph, Fig. 2, depicts a certain number of crystals and grain boundaries in an area that nearly corresponds to 1 × 1 μm2, which is the size of a single pixel in Fig. 8. This means that every single pixel (Fig. 8) contains a large number of grains/crystals and grain boundaries. Therefore, correlating the detection of M2 phase with morphological features such as grain boundary seems unlikely.

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.