Eichhorn Anna L, Dietz Christian
Physics of Surfaces, Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 2, 64287, Darmstadt, Germany.
Sci Rep. 2022 May 28;12(1):8981. doi: 10.1038/s41598-022-13065-9.
Combined in-plane and out-of-plane multifrequency atomic force microscopy techniques have been demonstrated to be important tools to decipher spatial differences of sample surfaces at the atomic scale. The analysis of physical properties perpendicular to the sample surface is routinely achieved from flexural cantilever oscillations, whereas the interpretation of in-plane sample properties via force microscopy is still challenging. Besides the torsional oscillation, there is the additional option to exploit the lateral oscillation of the cantilever for in-plane surface analysis. In this study, we used different multifrequency force microscopy approaches to attain better understanding of the interactions between a super-sharp tip and an HOPG surface focusing on the discrimination between friction and shear forces. We found that the lateral eigenmode is suitable for the determination of the shear modulus whereas the torsional eigenmode provides information on local friction forces between tip and sample. Based on the results, we propose that the full set of elastic constants of graphite can be determined from combined in-plane and out-of-plane multifrequency atomic force microscopy if ultrasmall amplitudes and high force constants are used.
平面内和平面外组合的多频原子力显微镜技术已被证明是在原子尺度上解读样品表面空间差异的重要工具。通过弯曲悬臂振荡通常可以实现对垂直于样品表面的物理性质的分析，而通过力显微镜对平面内样品性质的解释仍然具有挑战性。除了扭转振荡外，还有利用悬臂的横向振荡进行平面内表面分析的额外选择。在本研究中，我们使用不同的多频力显微镜方法，以更好地理解超尖锐尖端与HOPG表面之间的相互作用，重点是区分摩擦力和剪切力。我们发现横向本征模式适用于确定剪切模量，而扭转本征模式提供有关尖端与样品之间局部摩擦力的信息。基于这些结果，我们提出，如果使用超小振幅和高力常数，则可以通过平面内和平面外组合的多频原子力显微镜确定石墨的全套弹性常数。
