Department of Chemistry, Surface and Corrosion Science, Royal Institute of Technology, Drottning Kristinas Väg 51, SE-100 44 Stockholm, Sweden.
Ultramicroscopy. 2010 Mar;110(4):313-9. doi: 10.1016/j.ultramic.2010.01.002. Epub 2010 Jan 18.
A phase shift between the oscillatory motion and drive motion of an AFM-cantilever used for tapping mode AFM imaging can be related to adhesive and elastic properties of surface layers. In this study it was studied how optimal contrast between hard and soft surface layers can be achieved while minimizing the surface damage. This was investigated by performing classical force-distance measurements while driving the cantilever as in tapping mode imaging. The amplitude and phase response as a function of the average tip-surface separation was recorded. Five different cantilevers with a wide range of spring constants and four different tapping amplitudes were investigated and compared. Based on these experiments it is concluded that too stiff cantilever, high free tapping amplitude and low amplitude set point value often lead to surface damage, while too low spring constant and low free tapping amplitude result in poor phase image contrast. Intermediate values where little surface damage and significant image contrast are obtained were identified. In all cases it was observed that the best image contrast was obtained when the amplitude set point was chosen such that the amplitude during imaging was reduced to approximately 50% of the free amplitude.
用于敲击模式原子力显微镜成像的 AFM 悬臂的振荡运动和驱动运动之间的相移可以与表面层的粘附和弹性性质相关。在这项研究中，研究了如何在最小化表面损伤的同时实现硬层和软层之间的最佳对比度。这是通过在驱动悬臂进行敲击模式成像的同时进行经典的力-距离测量来研究的。记录了幅度和相位响应作为平均尖端-表面分离的函数。研究并比较了具有广泛弹性常数的五个不同的悬臂和四个不同的敲击幅度。基于这些实验，可以得出结论，过于刚性的悬臂、高的自由敲击幅度和低的幅度设定值值通常会导致表面损伤，而过低的弹性常数和低的自由敲击幅度会导致相位图像对比度差。确定了获得小表面损伤和显著图像对比度的中间值。在所有情况下，都观察到当选择幅度设定点使得成像期间的幅度减小到自由幅度的约 50%时，可以获得最佳的图像对比度。
