Atomic force microscopy for next generation metrology of surfaces

该项目的目的是了解针尖弯曲如何影响原子力显微镜(AFM)的图像质量，并开发新的方法来纠正引起的误差。原子力显微镜使用附着在柔性悬臂上的尖端来描绘样品的表面并形成图像。锋利的尖端可以探测到表面上非常微小的特征(精确到亚纳米，不到十亿分之一米)，而将尖端连接到灵活的悬臂上，就可以使用传统的激光检测信号。原子力显微镜是一种公认的纳米表面测量的关键工具。现代AFM针尖具有高纵横比(即薄而尖)，我们最近表明，这意味着当对表面成像时，针尖本身倾向于弯曲。不幸的是，使用传统的原子力显微镜方法，如果针尖弯曲，我们不再知道我们正在成像的是表面的哪一部分，我们获得的图像是扭曲的。对于工业计量学和科学研究，这造成了一个重要的误差来源，高达数十纳米，这在很大程度上被忽视了。使用我们最近开发的一种方法，学生将完全理解弯曲引起的误差在常规样品和成像硅片时(使用Infinitesima)。然后，学生将探索如何在成像过程中充分描述尖端弯曲的特征，以便揭示真实的表面形貌。

The aim of this project is to understand how tip bending affects image quality in atomic force microscopy (AFM) and develop new approaches to correct the errors caused. AFM uses a sharp tip attached to a flexible cantilever to trace out the surface of a sample and form an image. The sharp tip allows very small (down to sub-nanometre, less than a billionth of a metre) features on the surface to be sensed, and attaching the tip to a flexible cantilever allows the signal to be detected using a conventional laser. AFM is an established critical tool for nano-surface-metrology. Modern AFM tips have high aspect ratio (i.e. thin and sharp), and we have recently shown that this means the tip itself tends to bend when imaging surfaces. Unfortunately, using the conventional approach to AFM, if the tip bends, we no longer know which part of the surface we are imaging, and the picture we obtain is distorted. For industrial metrology purposes, and for scientific research, this creates an important source of error, up to tens of nanometres, which has largely been overlooked. Using an approach we recently developed the student will build a full understanding of the bending induced error in both conventional samples and when imaging silicon chips (with Infinitesima). The student will then explore how to fully characterise tip bending during imaging so that the true surface topography can be revealed.