Lievonen J, Ahlskog M
University of Jyväskylä, Nanoscience Center, P.O. Box 35 (YFL), FI-40014, Finland.
Ultramicroscopy. 2009 Jun;109(7):825-9. doi: 10.1016/j.ultramic.2009.03.028. Epub 2009 Mar 19.
Carbon nanotubes are usually imaged with the atomic force microscope (AFM) in non-contact mode. However, in many applications, such as mechanical manipulation or elasticity measurements, contact mode is used. The forces affecting the nanotube are then considerable and not fully understood. In this work lateral forces were measured during contact mode imaging with an AFM across a carbon nanotube. We found that, qualitatively, both magnitude and sign of the lateral forces to the AFM tip were independent of scan direction and can be concluded to arise from the tip slipping on the round edges of the nanotube. The dependence on the normal force applied to the tip and on the ratio between nanotube diameter and tip radius was studied. We show that for small values of this ratio, the lateral force signal can be explained with a simple geometrical model.
碳纳米管通常采用非接触模式的原子力显微镜（AFM）进行成像。然而，在许多应用中，如机械操纵或弹性测量，则使用接触模式。此时影响纳米管的力相当可观且尚未被完全理解。在这项工作中，我们在使用AFM以接触模式对碳纳米管成像的过程中测量了侧向力。我们发现，定性地说，作用于AFM针尖的侧向力的大小和方向与扫描方向无关，并且可以得出结论，这些侧向力是由针尖在纳米管的圆形边缘上滑动产生的。我们研究了侧向力对施加在针尖上的法向力以及纳米管直径与针尖半径之比的依赖性。我们表明，对于该比值的较小值，侧向力信号可以用一个简单的几何模型来解释。
