Jahng Junghoon, Lee Sunho, Hong Seong-Gu, Lee Chang Jun, Menabde Sergey G, Jang Min Seok, Kim Dong-Hyun, Son Jangyup, Lee Eun Seong
Hyperspectral Nano-imaging Team, Korea Research Institute of Standards and Science, Daejeon, 34113, Republic of Korea.
Department of Aerospace Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
Light Sci Appl. 2023 Nov 24;12(1):281. doi: 10.1038/s41377-023-01320-1.
We, for the first time, report the nanoscopic imaging study of anomalous infrared (IR) phonon enhancement of bilayer graphene, originated from the charge imbalance between the top and bottom layers, resulting in the enhancement of E mode of bilayer graphene near 0.2 eV. We modified the multifrequency atomic force microscope platform to combine photo-induced force microscope with electrostatic/Kelvin probe force microscope constituting a novel hybrid nanoscale optical-electrical force imaging system. This enables to observe a correlation between the IR response, doping level, and topographic information of the graphene layers. Through the nanoscale spectroscopic image measurements, we demonstrate that the charge imbalance at the graphene interface can be controlled by chemical (doping effect via Redox mechanism) and mechanical (triboelectric effect by the doped cantilever) approaches. Moreover, we can also diagnosis the subsurface cracks on the stacked few-layer graphene at nanoscale, by monitoring the strain-induced IR phonon shift. Our approach provides new insights into the development of graphene-based electronic and photonic devices and their potential applications.
我们首次报道了双层石墨烯异常红外（IR）声子增强的纳米级成像研究，其源于顶层和底层之间的电荷不平衡，导致双层石墨烯在0.2 eV附近的E模式增强。我们对多频原子力显微镜平台进行了改进，将光诱导力显微镜与静电/开尔文探针力显微镜相结合，构成了一种新型的混合纳米级光电力成像系统。这使得能够观察石墨烯层的红外响应、掺杂水平和形貌信息之间的相关性。通过纳米级光谱图像测量，我们证明了石墨烯界面处的电荷不平衡可以通过化学（通过氧化还原机制的掺杂效应）和机械（掺杂悬臂的摩擦电效应）方法来控制。此外，通过监测应变诱导的红外声子位移，我们还可以在纳米尺度上诊断堆叠的几层石墨烯的亚表面裂纹。我们的方法为基于石墨烯的电子和光子器件的发展及其潜在应用提供了新的见解。
