研究目的
To achieve controllable synthesis of high-quality hexagonal boron nitride (h-BN) with large domains and varied morphologies for industrial applications in 2D devices, by reducing nucleation density and altering growth mechanisms through silicon doping in copper substrates.
研究成果
The introduction of silicon into Cu substrates successfully reduces h-BN nucleation density by over two orders of magnitude and enables growth of large domains up to 0.25 mm with controllable morphologies from dendritic to triangular shapes. Silicon alters the growth mechanism to diffusion-limited mode, facilitated by enhanced dehydrogenation. This provides a novel pathway for large-scale, high-quality h-BN synthesis, with potential applications in 2D devices and beyond.
研究不足
The study is limited to Cu-Si alloy substrates with specific Si concentrations and growth temperatures; it may not generalize to other substrates or conditions. The phase-field model and simulations are qualitative and based on assumed parameters. Transfer processes could introduce defects, and characterization methods like Raman lack sensitivity for certain crystallographic details.
1：Experimental Design and Method Selection:
Low-pressure chemical vapor deposition (CVD) was employed using ammonia borane as a solid precursor to deposit h-BN on Cu-Si alloy substrates. The growth mechanism was studied through phase-field modeling and first-principles calculations to understand dynamics such as B-N diffusion, desorption, flux, and reactivity.
2：Sample Selection and Data Sources:
Cu-Si alloy substrates were prepared by melting mixtures of Si and Cu particles under hydrogen protection, with Si concentrations varied from 0 to 2.8 at%. Samples were characterized using scanning electron microscopy (SEM), Raman spectroscopy, and second harmonic generation (SHG) mapping.
3：8 at%. Samples were characterized using scanning electron microscopy (SEM), Raman spectroscopy, and second harmonic generation (SHG) mapping.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment includes a CVD furnace, quartz tube, annealing furnace, SEM (Zeiss EVO 18), Raman spectrometer (HORIBA LabRAM HR Evolution), and SHG setup with a femtosecond laser. Materials include Cu particles (99.99%), Si particles, ammonia borane, hydrogen gas, phosphoric acid, hydrofluoric acid, deionized water, and polymethyl methacrylate (PMMA) for transfer.
4：99%), Si particles, ammonia borane, hydrogen gas, phosphoric acid, hydrofluoric acid, deionized water, and polymethyl methacrylate (PMMA) for transfer.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Substrates were prepared by melting, polishing, and cleaning. CVD growth involved heating to target temperatures (e.g., 1000-1035°C) with ammonia borane source heated to 60-80°C. Transfer was done using a bubbling method with PMMA. Characterization included SEM imaging, Raman analysis at 532 nm laser, and SHG with 1100 nm laser.
5：Data Analysis Methods:
Nucleation density and coverage ratios were calculated from SEM images. Phase-field simulations modeled growth dynamics with parameters like diffusion coefficient and desorption time. First-principles calculations assessed dehydrogenation energy barriers.
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