研究目的
To develop a van der Waals epitaxial growth method for large single-crystal α-MoO3 nanosheets on various 2D materials and to characterize their crystal structure, band structure, and electrical properties.
研究成果
The van der Waals epitaxial growth method successfully produced high-quality single-crystal α-MoO3 nanosheets on various 2D materials. The epitaxially grown MoO3 has a large band gap of 2.9–3.2 eV and a small work function of 4.6 eV, making it highly n-doped. FETs based on α-MoO3 showed n-type transport behavior with an on/off ratio of 103 and field-effect mobility of 0.03 cm2/Vs. Layered oxide materials can be a missing block, wide-bandgap semiconductor, and insulating layer for future electronics based on 2D materials.
研究不足
The study is limited by the instability of monolayer MoO3 and the weak binding force at the heterointerface. Further optimization is needed to improve the field-effect mobility of MoO3 FETs.
1：Experimental Design and Method Selection:
The growth of α-MoO3 nanosheets was achieved by evaporating amorphous molybdenum oxide thin film in ambient conditions on 2D substrates. The crystal structure and band structure of the epitaxially grown α-MoO3 nanosheets were characterized using various techniques.
2：Sample Selection and Data Sources:
2D flakes of graphene, hBN, mica, MoSe2, and WSe2 were used as growth templates. The samples were characterized using Raman spectroscopy, AFM, TEM, XPS, UV-vis spectrometer, and GIXRD.
3：List of Experimental Equipment and Materials:
Raman spectroscopy (Renishaw Raman, inVia Confocal Raman microscope with a 532-nm excitation laser), AFM (Park systems, NX-10), TEM (JEOL, JEM-ARM 200F), XPS (Thermo Scientific, monochromatic Al Kα as X-ray source), UV-vis spectrometer (Agilent, Cary5000), GIXRD (Rigaku, SmartLab).
4：Experimental Procedures and Operational Workflow:
Mo films of 50-nm thickness were deposited on a Si substrate covered with 285-nm-thick SiO2 using a DC magnetron sputter. The deposited Mo film was placed onto a pre-heated heater of 550 °C in ambient conditions. The target substrate with 2D materials was placed upside down with a distance of 0.5 mm.
5：5 mm.
Data Analysis Methods:
5. Data Analysis Methods: The band gap of MoO3 was evaluated using Tauc’s equation from UV-vis absorption spectra. The work function was calculated from the UPS spectrum. The electrical properties were measured using a semiconductor analyzer (Keithely 4200).
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