研究目的
Investigating the use of laser reflectivity for in situ monitoring and control of the nucleation and growth kinetics of atomically-thin 2D materials during pulsed laser deposition.
研究成果
The laser reflectivity technique demonstrated high sensitivity for in situ monitoring of 2D material growth, showing excellent agreement with ex situ STEM analysis. The sigmoidal growth kinetics indicated a nucleation-limited initial phase followed by accelerated growth. This approach offers a simple and effective method for real-time control of 2D material deposition, with potential applications across various growth techniques.
研究不足
The calculations assumed ideal stacks of layers without roughness or imperfections. The dielectric constants used were room temperature values, not accounting for elevated deposition temperatures. The technique's sensitivity to nucleation stages may vary with material and deposition conditions.
1：Experimental Design and Method Selection:
The study utilized a pulsed laser deposition (PLD) setup with in situ laser reflectivity diagnostics to monitor the growth of MoSe2 layers. The optical contrast was optimized through Fresnel’s equations considering layer thickness, substrate, laser wavelength, incidence angle, and polarization.
2：Sample Selection and Data Sources:
MoSe2 films were deposited on SiO2/Si substrates with varying SiO2 thicknesses. Atomic resolution STEM analysis was used for ex situ validation of layer thickness and coverage.
3：List of Experimental Equipment and Materials:
A KrF excimer laser (248 nm) for PLD, HeNe laser (632.8 nm) for reflectivity monitoring, Si photodiodes with 633 nm filters, and Keithley 2400 SourceMeter for data acquisition.
4：8 nm) for reflectivity monitoring, Si photodiodes with 633 nm filters, and Keithley 2400 SourceMeter for data acquisition.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The substrate was heated to 600°C in vacuum. The PLD process was monitored in real-time using the HeNe laser reflectivity setup, with growth arrested at specific reflectivity points for STEM analysis.
5：Data Analysis Methods:
Reflectivity data was compared with theoretical predictions based on Fresnel’s equations. Growth kinetics were modeled using an autocatalytic kinetic model to describe nucleation and growth stages.
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