研究目的
To investigate and demonstrate the first gate-controlled field emission from a WSe2 monolayer, leading to the development of a vertical field emission transistor for vacuum electronics applications.
研究成果
The study successfully demonstrates the first vertical field emission transistor based on a WSe2 monolayer, with gate-modulated emission current stable under ～100 V μm?1 electric field. Optimization through edge emission, reduced contact resistance, and high-k dielectrics could enhance performance for vacuum electronics applications.
研究不足
The device exhibits low mobility (～0.01 cm2 V?1 s?1) and high contact resistance due to Schottky barriers, limited by interfacial trap density and SiO2 gate dielectric. Field emission is from the flat part of the flake, not exploiting sharp edges for higher enhancement factors. Operational voltages are high, and device stability can be affected by adsorbates and defects.
1：Experimental Design and Method Selection:
The study involved synthesizing WSe2 monolayers via chemical vapor deposition (CVD) on SiO2/Si substrates, fabricating back-gated transistors with Ni contacts, and characterizing electrical and field emission properties under high vacuum using a semiconductor parameter analyzer and scanning electron microscopy (SEM) setup.
2：Sample Selection and Data Sources:
WSe2 flakes were grown on heavily doped p-Si substrates with 300 nm SiO2, selected based on optical microscopy, Raman, and photoluminescence spectroscopy to identify monolayers.
3：List of Experimental Equipment and Materials:
Equipment includes a two-zone quartz tube furnace for CVD, GATAN 682 Precision Etching and Coating System (PECS) for sputtering, Zeiss LEO 1530 SEM chamber for measurements, Keithley 4200-SCS semiconductor parameter analyzer, piezoelectric-driven arms with W-tips, and materials such as WOx seed layer, Se, Ar:H2 gas, Ni/Au contacts.
4：Experimental Procedures and Operational Workflow:
Steps include CVD growth of WSe2, patterning Ni/Au contacts via electron beam lithography, electrical measurements in high vacuum, field emission measurements with W-tip anode at controlled distances, and data collection for output and transfer characteristics.
5：Data Analysis Methods:
Analysis involved Fowler-Nordheim theory for field emission, calculation of field enhancement factors, mobility estimation using transistor equations, and statistical evaluation of current-voltage characteristics.
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