主题：【讨论】关于非接触模式和敲击模式AFM的比较讨论

阁下应该是非常懂AFM的，有个问题暂时请教：能否详细讲解一下非接触模式和敲击模式AFM的工作原理？把这个问题搞清楚了什么问题都清楚了。大家也可以讨论，比较比较优缺点什么的。

原文由 romantic25 发表:
相信做AFM的都知道，Tapping模式在测量表面软硬程度不同的样品时候，得到的是针尖压入后的结果，会导致测量的并非样品本身真实形貌，而是变形后的形貌。
  因此真正的非接触测量才能测量出真正的表面形貌。
  不知道各位有何见解，欢迎讨论！

一般不是说non-contact是非主流的技术吗？

我相信做AFM的都了解这些基本的原理的，关键是大家对于各模式使用的感觉。才希望大家来讨论。

要不你给点比较详细的non-contact的资料看看，现在介绍non-contact的资料太少了，呵呵

原文由 romantic25 发表:
我相信做AFM的都了解这些基本的原理的，关键是大家对于各模式使用的感觉。才希望大家来讨论。

非也，不是所有人都懂！肯定还有不少人不完全明白，既然要讨论两种模式的不同，首先得从原理开始！所以，希望能够明白人先把原理讲清楚.

不太懂
对于一般新貌表征，好像首选Tapping Mode，对样品损伤小，特别是生物样；没接触过non-contact

抱歉了各位,这几天有点忙.我会尽快整理整理资料然后发送上来.

Non-contact mode is free from drawback. In this mode, the probe operates in attractive force region and tip-sample interaction is minimized.

The use of non-contact mode allowed scanning without influencing the shape of the microdrops by the tip-sample forces. In addition, this mode is the only AFM-mode that enables true atomic resolution

cyanapple版友，如果copy东西，请copy全，否则是误导大家
http://www.spmtips.com/products/cantilevers/catalog/noncontact/

Noncontact AFM mode
Surfaces of fragile samples can be easily destroyed when scanning in contact mode due to strong tip-sample interactions. Non-contact mode is free from this drawback. In this mode, the probe operates in attractive force region and tip-sample interaction is minimized. In Fig. 1, you can see image of microdrops of a liquid n-alkane on the silinized silicon substrate. The use of non-contact mode allowed scanning without influencing the shape of the microdrops by the tip-sample forces. In addition, this mode is the only AFM-mode that enables true atomic resolution (see fig. 2).

The tip-sample interaction in non-contact mode is much weaker, than one in contact mode.To enhance the sensitivity to attractive forces, modulation technique is used in this mode. In this technique, scanning tip is oscillated close to the sample at a frequency near to the resonant frequency of the cantilever. The tip-sample interaction forces change in both the effective resonant frequency and the amplitude of oscillations. During the scanning, the feedback loop keeps constant tip-sample distance by maintaining the resonant frequency of oscillation (frequency-modulation mode) or the amplitude of oscillation (amplitude-modulation mode).

To improve the resolution in Non-contact mode, one needs to enhance the sensitivity to short-range tip-sample forces. For the reason, small amplitudes of oscillation and small tip-sample distance are commonly used. But operation at distances near to the sample demands fine tip-force control and the absence of surface contamination. That is why this technique is mostly used in ultrahigh vacuum.

In most cases, the cantilever of choice for this mode is the one having high spring constant of 20-100 N/m so that it does not stick to the sample surface at small amplitudes. Between two cantilevers having the same spring constant, it is better to use the one with the higher resonant frequency. This lever is generally faster and less noisy. Low-frequency cantilevers are used with AFM systems that do not support probes with short lever arms.

原文由 cyanapple 发表:
Non-contact mode is free from drawback. In this mode, the probe operates in attractive force region and tip-sample interaction is minimized.

The use of non-contact mode allowed scanning without influencing the shape of the microdrops by the tip-sample forces. In addition, this mode is the only AFM-mode that enables true atomic resolution