研究目的
Investigating the anisotropic friction domains of MoS2 grown by chemical vapor deposition (CVD) under various sulfur pressure conditions and by mechanical exfoliation process, and understanding the universality of anisotropic frictional behaviors in 2D materials.
研究成果
The study demonstrates the universality of anisotropic friction domains in 2D materials with hexagonal honeycomb structures, attributed to linearly aligned ripples along crystallographic axes due to inhomogeneous strain fields. This understanding is crucial for the application of 2D materials in electronic devices and nanomechanical systems.
研究不足
The study is limited by the resolution of AFM in detecting very smooth ripples with low aspect ratios. The origin of anisotropic friction domains is still debated, with competing explanations involving strain-induced ripples versus periodic chemical adsorbates.
1:Experimental Design and Method Selection:
The study involved the growth of MoS2 by CVD under various sulfur pressure conditions and mechanical exfoliation. Friction force microscopy (FFM) and atomic force microscopy (AFM) were used to study the anisotropic friction domains. Second-harmonic generation (SHG) measurements were conducted to determine the crystallographic orientation.
2:Sample Selection and Data Sources:
MoS2 samples were grown by CVD and mechanically exfoliated. The samples were characterized using FFM, AFM, and SHG.
3:List of Experimental Equipment and Materials:
Park Systems XE-100 AFM system, silicon AFM tips (Nanosensors PPP-LFMR), MikroMasch Hi’Res-C15/Cr-Au probe, Ti-sapphire femtosecond laser (Cohernet Vitara-T), photomultiplier tube.
4:Experimental Procedures and Operational Workflow:
MoS2 crystals were grown by CVD, characterized by FFM and AFM, and their crystallographic orientation was determined by SHG. The friction anisotropy was studied by rotating the sample and measuring the TFM signal.
5:Data Analysis Methods:
The TFM signal was analyzed to determine the periodicity and shift between domains. SHG intensity was analyzed to determine the crystallographic orientation.
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