研究目的
Investigating the effects of film thickness on the microstructure, surface morphology, and thermochromic performance of vanadium dioxide (VO2) thin films grown by magnetron sputtering.
研究成果
The research demonstrates that film thickness significantly influences the microstructure, optical, and electrical properties of VO2 thin films. Thicker films exhibit improved crystallinity, larger grain sizes, lower optical band gaps, enhanced IR switching efficiency, but reduced visible transmittance. A thickness range of 80-100 nm offers a balanced combination of high visible transmittance and good solar switching efficiency, making it suitable for smart window applications. The phase transition temperature is lower than that of single-crystal VO2, attributed to factors like intrinsic stress and oxygen vacancies. Future studies could optimize other deposition parameters and explore applications in laser protection or other devices.
研究不足
The study is limited to VO2 films on soda-lime glass substrates prepared by DC magnetron sputtering at a specific low temperature (320 °C). The findings may not generalize to other deposition methods, substrates, or temperatures. The EDS measurements are semi-quantitative, and oxygen contributions from the substrate could affect accuracy. The range of thicknesses studied (12-264 nm) might not cover all possible variations, and industrial scalability aspects are not deeply explored.
1：Experimental Design and Method Selection:
VO2 films were deposited on soda-lime glass using direct current magnetron sputtering at 320 °C to study the influence of film thickness on properties. The method was chosen for its advantages in producing high packing density, uniform large-area coatings, and potential for industrialization.
2：Sample Selection and Data Sources:
Samples with varying thicknesses (12, 79, 102, 154, 173, 216, 264 nm) were prepared by controlling deposition time. Thickness was measured using a step profiler.
3：List of Experimental Equipment and Materials:
Equipment includes a DC magnetron sputtering system with a vanadium target, step profiler (Bruker Dektak XT), X-ray diffractometer (Rigaku Ultima IV), Raman microscope (Horiba Scientific XploRA PLUS), spectrophotometer (Lambda 950), SEM (Zeiss Supra 5S Sapphire), four-point probe system with Keithley 2400 source meter, and Peltier heating stage. Materials include soda-lime glass substrates, high-purity vanadium target (99.99%), Ar and O2 gases.
4：99%), Ar and O2 gases.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The vacuum chamber was pumped to 6×10^-4 Pa, pre-sputtering was done for 10 min, sputtering with Ar (40 sccm) and O2 (1.8 sccm) at 0.5 Pa pressure, 120 W power, -125 V bias voltage, and 320 °C temperature. Thickness was varied by deposition time. Characterization involved XRD, Raman spectroscopy, UV/VIS/NIR transmittance measurements, SEM imaging, and electrical resistivity measurements with temperature control.
5：8 sccm) at 5 Pa pressure, 120 W power, -125 V bias voltage, and 320 °C temperature. Thickness was varied by deposition time. Characterization involved XRD, Raman spectroscopy, UV/VIS/NIR transmittance measurements, SEM imaging, and electrical resistivity measurements with temperature control.
Data Analysis Methods:
5. Data Analysis Methods: XRD patterns were analyzed for crystallinity and grain size using Scherrer's equation. Raman spectra identified vibrational modes. Transmittance spectra were used to calculate luminous transmittance and solar switching efficiency. Electrical resistivity data were plotted to determine phase transition temperature and hysteresis.
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