激光偏振拉曼的CVD多晶石墨烯表征

石墨烯具有优异的物理化学性质,在MEMS器件、光电检测材料、柔性显示屏、新能源电池、复合材料等方面成为研究热点。目前大面积石墨烯制备主要依赖于化学气相沉积技术(chemical vapor deposition, CVD),但其生长的晶体质量直接影响到电化学特性和实际应用,因此需要一种快速而准确的表征方法。实验利用背向散射的偏振激光散射装置测量CVD生长的石墨烯拉曼光谱。通过分析实验获得的300 nm SiO2/Si基底上的单层、五层和十层左右的石墨烯角分辨偏振拉曼光谱,发现单层生长的石墨烯偏振特性与机械剥离单晶石墨烯一致;随着层数的增加,G峰偏振响应差异更加明显,表现出明显的椭圆特性;在不同石墨烯层数上的D峰也呈现出一定的偏振响应差异性。偏振拉曼测试结果表明目前CVD生长的缺陷和多晶特性与石墨烯层数呈现正相关特征。

Characterization of polycrystalline graphene based CVD by laser polarization Raman

Graphene has excellent physical and chemical properties, and has become a research hotspot in the fields of MEMS devices, photoelectric detection materials, flexible display screens, new energy batteries and composite materials. At present, the preparation of large area graphene mainly depends on chemical vapor deposition (CVD), but the crystal quality of graphene growth directly affects the electrochemical characteristics and practical applications, so a fast and accurate characterization method is needed. Raman spectra of graphene grown by CVD were measured by backscattering polarized laser scattering device. Angular resolved polarization Raman spectra of graphene on 300 nm SiO₂/Si substrates were analyzed. It was found that the polarization characteristics of graphene grown in single layer were consistent with those of mechanically stripped graphene. The polarization response of G peak was more distinct with the increase of the number of layers, showing obvious elliptical characteristics. In graphene samples with different layers, the defects in the samples showed obvious D peaks and polarization responses due to the increase of layers. The polarization states of the 2D peaks were not significantly different in different samples and were not affected by the number of layers. Polarization Raman measurements show that the defects and polycrystalline properties of CVD growth are positively correlated with the number of graphene layers.