散射式太赫兹扫描近场光学显微技术研究

基于散射式近场探测原理,设计并搭建了散射式太赫兹扫描近场光学显微系统(THz s-SNOM),实现了纳米量级空间分辨率的太赫兹近场显微成像测量。该系统以输出频率范围为0.1~0.3THz的太赫兹倍频模块为发射源,通过纳米探针的针尖产生纳米光源与样品相互作用,并将样品表面的倏逝波转化为可在远场测量的辐射波。通过探针逐点扫描样品表面,同时获得了样品表面的形貌图和太赫兹近场显微图。该系统的显微分辨率取决于探针针尖的曲率半径,而与太赫兹波的波长无关。使用该系统测量了金薄膜/硅衬底样品和石墨烯样品的近场显微图,结果表明,近场显微的空间分辨率优于60nm,波长与空间分辨率之比高达λ/26000。

Study on scattering-type terahertz scanning near-field optical microscopy

Based on the theory of near-field scanning detection,a scattering terahertz scanning near-field optical microscopy(THz s-SNOM)system is designed and built.The system achieves nanoscale spatial resolution,breaking the diffraction limit.Using a frequency multiplier module with an operating frequency of 0.1?0.3 THz as the emission source,the THz beam is focused onto the tip of an atomic force microscope(AFM)probe.The tip of the needle acts as a nano-light source,interacting with the sample.After the evanescent waves are converted into radiation waves,they are collected by the parabolic mirrors and imaged point by point in the far field.The topography image of the sample surface and the near-field amplitude map without background can be obtained simultaneously.The resolution of the system depends on the tip radius of the AFM probe,which is independent on the wavelength of the beam used.The near-field image obtained by scanning different samples shows that the resolution is less than 60 nm and spatial resolution achievesλ/26000.