研究目的
To investigate the effect of the oxygen pressure in the deposition chamber on the material properties of titanium oxide thin films, including mechanical and tribological properties such as modulus of elasticity, hardness, and adhesion force.
研究成果
The research concludes that decreasing oxygen pressure during deposition increases film thickness and roughness, improves mechanical properties (hardness and modulus of elasticity), but reduces adhesion force. These changes are attributed to variations in grain size and film density. The findings are significant for optimizing TiO2 thin films for applications such as thermoelectric devices, emphasizing the importance of deposition conditions on material performance. Future studies could explore a broader range of parameters or long-term durability.
研究不足
The study is limited to specific deposition conditions (e.g., substrate temperature fixed at 700°C, laser parameters constant) and may not account for other variables like different substrates or laser settings. The use of AFM for measurements might have resolution constraints, and the focus on oxygen pressure effects may overlook interactions with other deposition parameters. Potential optimizations could include varying more parameters or using complementary characterization techniques.
1：Experimental Design and Method Selection:
The study uses Pulsed Laser Deposition (PLD) to fabricate TiO2 thin films under varying oxygen pressures. Characterization is performed using atomic force microscopy (AFM) with nanoindentation and spectroscopy modules to measure thickness, roughness, mechanical properties (hardness and modulus of elasticity), and tribological properties (adhesion force). The Oliver and Pharr method is employed for data analysis from load-displacement curves.
2：Sample Selection and Data Sources:
N-doped Si (100) substrates (5mm×10mm) are used, cleaned in acetone, ethanol, water, and ultrasonic baths, then rinsed with distilled water. TiO2 films are deposited from a rutile target.
3：List of Experimental Equipment and Materials:
Equipment includes a PLD system with a KrF excimer laser (λ=248nm, pulse duration 20ns), AFM (XE70 model by Park Systems Co.) with nanoindentation module, diamond AFM tip, and Si3N4 AFM tip for adhesion tests. Materials include TiO2 target, N-doped Si substrates, acetone, ethanol, distilled water.
4：Experimental Procedures and Operational Workflow:
Substrate temperature is maintained at 700°C during deposition. Laser fluence is set to 2J/cm2 with a frequency of 5Hz for 1 hour. Oxygen pressure is varied from 1×10?? mbar (vacuum) to 3×10?3 mbar. AFM measurements are conducted at 20°C and 40% relative humidity. Thickness is measured by scanning film edges, roughness by tapping mode, mechanical properties by nanoindentation with a force of 40 μN, and adhesion force by spectroscopy-in-point mode.
5：Data Analysis Methods:
Data are analyzed using the Oliver and Pharr method for hardness and modulus of elasticity from load-displacement curves. Roughness parameters (e.g., Ra) are derived from AFM scans. Adhesion force is determined from the unloading part of AFM curves.
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