Nanometric locking of the tight focus for optical microscopy and tip-enhanced microscopy
Nanometric locking of the tight focus for optical microscopy and tip-enhanced microscopy
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DOI：
10.1088/0957-4484/23/46/465203
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发表时间：
2012-11-23
期刊：
影响因子：
3.5
通讯作者：
Kawata, S.
中科院分区：
文献类型：
--
作者：
Hayazawa, N.;Furusawa, K.;Kawata, S.
我们已经成功地将光学显微镜的样品表面上的紧密聚焦稳定在+/- 1.0 nm范围内，持续时间几乎不受限制。紧聚焦的随时间变化的热漂移和样品表面的机械倾斜由基于电容传感器的非光学装置同时感测，并进行实时补偿。这种非光学方案是有希望的抑制背景光源的光学显微镜。焦点稳定对于界面处的显微测量至关重要，特别是在扫描大表面积时，因为样品基底总是存在一定量的机械倾斜，这会降低图像的对比度。当对纳米级材料如碳纳米管或硅纳米线成像时，需要相对于这些样品更严格的焦点位置的纳米稳定性，否则通常难以解释观察结果。此外，样品体积越小，信号变得越小，导致在每个位置处的长曝光时间。从这个意义上说，紧密聚焦的长期稳定性对于微观大面积扫描和纳米尺寸样品扫描（高分辨率/大面积成像）都是必不可少的。此外，最近开发的针尖增强显微镜需要针尖、样品和焦点位置的相对位置的长期稳定性。我们能够以相同的方式成功地证明尖端增强显微镜的稳定性改善。紧聚焦的稳定性使我们能够进行长期和稳健的测量，而不会使光学信号发生任何退化，从而能够实现具有良好再现性和高精度的真正纳米光学成像。该技术是一个简单的附加任何类型的光学显微镜。
We have successfully stabilized the tight focus onto the sample surface of an optical microscope within +/- 1.0 nm for a virtually unlimited time duration. The time-dependent thermal drift of the tight focus and the mechanical tilt of the sample surface were simultaneously sensed by a non-optical means based on a capacitive sensor and were compensated for in real-time. This non-optical scheme is promising for the suppression of background light sources for optical microscopy. The focus stabilization is crucial for microscopic measurement at an interface, particularly when scanning a large surface area, because there is always a certain amount of mechanical tilt of the sample substrate, which degrades the contrast of the image. When imaging nanoscopic materials such as carbon nanotubes or silicon nanowires, more stringent nanometric stabilization of the focus position relative to such samples is required, otherwise it is often difficult to interpret the results from the observations. Moreover, the smaller the sample volume is, the smaller the signal becomes, resulting in a long exposure time at each position. In this sense, long-term stability of the tight focus is essential for both microscopic large area scanning and nanosized sample scanning (high-resolution/large-area imaging). In addition, the recently developed tip-enhanced microscopy requires long-term stability of the relative position of the tip, sample and focus position. We were able to successfully demonstrate a stability improvement for tip-enhanced microscopy in the same manner. The stabilization of the tight focus enables us to perform long-term and robust measurements without any degradation of optical signal, resulting in the capability of true nanometric optical imaging with good reproducibility and high precision. The technique presented is a simple add-on for any kind of optical microscope.