Mapping nanoscale carrier confinement in polycrystalline graphene by terahertz spectroscopy
Mapping nanoscale carrier confinement in polycrystalline graphene by terahertz spectroscopy
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DOI：
10.1038/s41598-024-51548-z
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发表时间：
2024-02-07
影响因子：
4.6
通讯作者：
Boggild，Peter
中科院分区：
文献类型：
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作者：
Whelan，Patrick R.;De Fazio，Domenico;Boggild，Peter
太赫兹时域光谱（THz-TDS）可用于绘制石墨烯中电导率、载流子密度和载流子迁移率等电性能的空间变化。在这里，我们考虑通过化学气相沉积在锗上生长的晶圆级石墨烯，由于生长过程中衬底的重建而具有不均匀性和小域。太赫兹电导率谱符合现象学德鲁德-史密斯模型对由边界和线缺陷引起的非各向同性散射的导体的预测。我们比较了太赫兹- tds测定的载流子平均自由程与拉曼光谱测定的平均缺陷距离以及透射电子显微镜测定的晶界尺寸。结果表明，即使石墨烯颗粒内小于5°的小角度取向变化也会影响散射行为，这与晶界对后向散射的显著贡献一致。
Terahertz time-domain spectroscopy (THz-TDS) can be used to map spatial variations in electrical properties such as sheet conductivity, carrier density, and carrier mobility in graphene. Here, we consider wafer-scale graphene grown on germanium by chemical vapor deposition with non-uniformities and small domains due to reconstructions of the substrate during growth. The THz conductivity spectrum matches the predictions of the phenomenological Drude–Smith model for conductors with non-isotropic scattering caused by backscattering from boundaries and line defects. We compare the charge carrier mean free path determined by THz-TDS with the average defect distance assessed by Raman spectroscopy, and the grain boundary dimensions as determined by transmission electron microscopy. The results indicate that even small angle orientation variations below 5° within graphene grains influence the scattering behavior, consistent with significant backscattering contributions from grain boundaries.