低维纳米材料的近场光学表征  

Near-field optical characterization of low-dimensional nanomaterials

作　　者：胡德波[1] 戴庆[1] Debo Hu;Qing Dai(Division of Nanophotonics,National Center for Nanoscience and Technology,Beijing 100190,China)

机构地区：[1]国家纳米科学中心纳米光子学研究部,北京100190

出　　处：《科学通报》2018年第35期3747-3759,共13页Chinese Science Bulletin

基　　金：国家重大科学研究计划(2015CB932400);国家自然科学基金(11704085);中国科学院仪器研制项目资助

摘　　要：光学显微术作为一种快速、无损的表征手段在材料研究领域得到了广泛应用,但是受光的波动性制约,传统远场光学显微术无法满足低维纳米材料表征对亚衍射极限空间分辨率的需求.近年来,随着散射式扫描近场光学显微术(s-SNOM)的发展进步,光学成像的空间分辨率已经达到10nm量级,突破了光学衍射极限.本文首先简要阐述了s-SNOM的成像原理,然后按照s-SNOM的工作模式分类介绍了其在低维纳米材料表征领域的应用研究进展,最后对s-SNOM技术未来的发展及应用进行展望.Due to the wave nature of light,the spatial resolution of traditional far-field optical microscopy is fundamentally prohibited to be much smaller than the wavelength,thus cannot fulfill the requirement of nano-characterization of low-dimensional materials.This diffraction limit can be circumvented by the optical version of scanning probe microscopy via incorporating the near-field optical information into the imaging process.In the last one and a half decades,scanning near-field optical microscopic techniques,especially scattering-type scanning near-field optical microscopy(s-SNOM),have undergone tremendous development.The wavelength independent spatial resolution of s-SNOM goes far beyond the diffraction limit,leading to an explosive amount of applications that spread throughout the field of materials science.The instrument of s-SNOM is a delicate combination of optical and scanning probe techniques.It utilizes the sharp tip of an atomic force microscope(AFM) probe to achieve nanoscale spatial resolution.Specifically,the light beam from a source is focused onto the apex of the AFM tip by a parabolic mirror.The tip serves as a nanoscale light confiner and enhancer,inducing a strong electromagnetic field(hot spot) underneath the tip apex.When the tip is brought into contact with the investigated sample,this field is modified by its interaction with the sample and carries near-field information of the sample.Then the tip acting as an optical antenna scatters the near-field information into far-field.The back-scattered near-field signals are feed into a photodetector to register a near-field image of the sample.By modulating the near-field signal via tapping the AFM tip and demodulating at the high order harmonics of the tip-tapping frequency,the noise from the background and stray light can be greatly suppressed.Since the near-field hot spot is on the same scale with the tip apex,the spatial resolution of s-SNOM is predominantly defined by the dimensions of the tip;a value of 20 nm is routinely achievable with comm

关 键 词：衍射极限 低维材料 近场成像 电磁模式 纳米红外 

分 类 号：TB383.1[一般工业技术—材料科学与工程]