研究目的
Investigating the influence of thickness and post deposition annealing temperature on the structural and optical properties of thermally evaporated molybdenum oxide films.
研究成果
Molybdenum oxide films show amorphous nature in as-deposited and low-temperature annealed states, transitioning to polycrystalline with α-MoO3 and MoO2 phases at 250°C annealing. Optical properties, including refractive index, band gap, and conductivity, are significantly influenced by thickness and annealing temperature, with improvements in homogeneity and optical response at lower thicknesses and higher annealing.
研究不足
The study is limited to thermally evaporated films on glass substrates; other deposition techniques or substrates are not explored. The annealing temperatures are up to 250°C, and higher temperatures might yield different results. Thickness measurement discrepancies exist, especially for thicker films.
1：Experimental Design and Method Selection:
The study uses thermal evaporation for film deposition, with variations in source-substrate distance and post-deposition annealing temperature. Characterization methods include XRD for structural analysis, SEM for morphology, UV-Vis spectrophotometry for optical properties, and PL spectroscopy.
2：Sample Selection and Data Sources:
Molybdenum oxide films are deposited on glass substrates at different source-substrate distances (6 to 12 cm) and annealed at temperatures from 27°C to 250°C. Samples are coded S1 to S12 based on parameters.
3：List of Experimental Equipment and Materials:
Equipment includes a thermal evaporation unit (HINDHIVAC 12″ vacuum coating unit, 12A4D), SEM (JEOL JSM-IT 300), XRD (Rigaku Ultima (IV)), UV-Vis spectrophotometer (Shimadzu UV-VIS 2600), spectrofluorometer (Horbia JovinYvon Fluromax-4). Materials include molybdenum oxide powder (Aldrich, purity 99.97%) and glass substrates.
4：4). Materials include molybdenum oxide powder (Aldrich, purity 97%) and glass substrates.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Substrates are cleaned and annealed before deposition. Films are deposited at elevated substrate temperature (~100°C) under base pressure ~2×10^{-5} Torr. Post-deposition annealing is done for 1 hour at specified temperatures. Thickness is measured using Tolansky method, SEM cross-sections, and optical methods. Structural, morphological, and optical characterizations are performed as per standard protocols.
5：Data Analysis Methods:
Data analysis includes Scherrer's formula for crystallite size, R. Swanepoel's envelope method for refractive index and thickness, Tauc plots for band gap, Urbach energy calculation, and Lorentz-Lorenz equation for film density.
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