Confocal Raman microscopy: Why the depth resolution and spatial accuracy can be much worse than you think
Confocal Raman microscopy: Why the depth resolution and spatial accuracy can be much worse than you think
复制标题
DOI：
10.1366/0003702001948439
复制
发表时间：
2000-10-01
影响因子：
3.5
通讯作者：
Everall, NJ
中科院分区：
文献类型：
--
作者：
Everall, NJ
本文介绍了对共焦拉曼显微镜的深度分辨率和空间精度的折射的影响的持续研究。以前的工作表明，界面的表观位置，以及它们的宽度，是严重的错误时，“光学切片”进行高功率冶金物镜（商业共焦拉曼仪器的常见配置）。提出了简单的方程模型，这些影响只给出了物镜的数值孔径和样品的折射率。本文将这些研究延伸到测量的位置和厚度的掩埋结构，并显示如何折射理论提供了一个很好的基础，解释拉曼强度-深度剖面已获得的光学切片的复杂结构。总结一下这个问题的严重性，典型的情况是，一个埋层的视厚度和位置深度大约是真实值的一半，因此，在解释强度-深度剖面时，折射校正是至关重要的。为了使影响最小化，可以使用专门的物镜（例如，油浸物镜）以减少样品表面的折射。数据表明，与这样的目标获得的结构的表观位置和厚度更接近实际值，即使当样品的指数是不完全匹配的耦合液。如果要尝试通过光学切片进行深度剖析，则强烈建议使用浸没物镜。
This paper describes continuing studies on the effect of refraction on the depth resolution and spatial accuracy of confocal Raman microscopy. Previous work showed how the apparent position of interfaces, and their breadth, was grossly in error when "optical sectioning" was carried out with a high-power metallurgical objective (the usual configuration for commercial confocal Raman instruments). Simple equations were presented which model these effects given only the numerical aperture of the objective and sample refractive index. This paper extends these studies to the measurement of the position and thickness of buried structures and shows how the refraction theory provides a good basis for interpreting Raman intensity-depth profiles that have been acquired by optical sectioning of complex structures. To summarize the magnitude of the problem, it is typical for the apparent thickness and positional depth of a buried layer to be about half of the true values-hence, correcting for refraction is critical when interpreting intensity-depth profiles. In order to minimize the effects it is possible to use a specialized objective (e.g., an oil immersion objective) to reduce refraction at the sample surface. Data are presented which show that the apparent position and thickness of structures obtained with such an objective are much closer to the actual values, even when the sample index is not perfectly matched by the coupling fluid. The use of immersion objectives is highly recommended if depth profiling by optical sectioning is to be attempted.