Tapping mode

For membranes, mainly contact mode (C-AFM), non-contact mode (NC-AFM), and tapping mode (TM-AFM, intermittent contact mode) are used. 

In C-AFM, the tip makes physical contact with the sample. As the tip is moved across the sample, the contact force causes the cantilever to bend according to changes in topography. In constant force mode, the tip is constantly adjusted to maintain a constant deflection, and therefore constant height above the surface. It is this adjustment that is displayed as data. However, the ability to track the surface in this manner is limited by the feedback circuit. Sometimes the tip is allowed to scan without this adjustment, and one measures only the deflection. This is useful for small, high-speed atomic resolution scans, and is known as variable-deflection mode. 

Provides three-dimensional information nondestructively, with 1.5 nm resolution laterally and 0.05 nm resolution vertically 

Uses strong repulsive forces acting between the tip and the sample 

Analyzes insulators and conductors easily (AFM is not based on conductivity) 

---

Zong Q, inniss D, K]oiier K and Eiings V B 1993 Fractured poiymer/siiica fiber surface studied by tapping mode atomic force microscopy Surf. Sc/. Lett. 290 L688... 

Flansma P K ef a/1994 Tapping mode atomic force microscopy in iiquids Appl. Phys. Lett. 64 1738... 

Dhinojwala A and Granick S 1997 Surface forces In the tapping mode solvent permeability and hydrodynamic thickness of adsorbed polymer brushes Macromoiecuies 30 1079-85... 

Fig. 6. Van der Waals potential energy-distance curve showing regions of operation of contact, noncontact, and intermittent contact or tapping-mode afm...

Fig. 5.2. Principle of AFM. The sample symbolized by the circles is scanned by means of a piezoelectric translator. The piezo crystal and the oscillator is only needed for tapping mode operation.

Tamayo, J. and Garcia, R., Effects of elastic and inelastic interactions on phase contrast images in tapping-mode scanning force microscopy. Appl. Phys. Lett., 71(16), 2394-2396 (1997). 

Tamayo, J. and Garcia, R., Relationship between phase shift and energy dissipation in tapping-mode scanning force microscopy. Appl Phys. Lett., 73(20), 2926-2928 (1998). Gotsmann, B., Seidel, C., Anezykowski, B. and Fuchs, H., Conservative and dissipative tip-sample interaction forces probed with dynamic AFM. Phys. Rev. B Condens. Matter, 60, 11051-11061 (1999). 

Bar, G., Delineau, L., Hafele, A. and Whangbo, M.H., Investigation of the stiffness change in, the indentation force and the hydrophobic recovery of plasma-oxidized polydimethyl-siloxane surfaces by tapping mode atomic force microscopy. Polymer, 42(8), 3627-3632 (2001). 

To minimize effects of friction and other lateral forces in the topography measurements in contact-modes AFMs and to measure topography of the soft surface, AFMs can be operated in so-called tapping mode [53,54]. It is also referred to as intermittent-contact or the more general term Dynamic Force Mode" (DFM). A stiff cantilever is oscillated closer to the sample than in the noncontact mode. Part of the oscillation extends into the repulsive regime, so the tip intermittently touches or taps" the surface. Very stiff cantilevers are typically used, as tips can get stuck" in the water contamination layer. The advantage of tapping the surface is improved lateral resolution on soft samples. Lateral forces... 

FIGURE 2.14 Tapping mode phase morphology of the nanocomposites (a) poly[styrene-(ethylene-co-butylene)-styrene] (SFBS)-Cloisite 20A and (b) its 3D image. (From Ganguly, A., Sarkar, M.D., and Bhowmick, A.K., J. Polym. ScL, Part B Polym. Phys., 45, 52, 2006. Courtesy of Wiley InterScience.)... 

FIGURE 12.10 Tapping mode atomic force microscopy (AFM) images of the section analyzes of ethylene-propylene-diene monomer (EPDM) rubber-melamine fiber composites. A, composite containing no dry bonding system B, composite containing resorcinol, hexamine, and silica in the concentrations 5, 3, and 15 phr, respectively. 

A change in the amphtude of oscillating AFM probe is chosen for a control of tip-sample force interactions in tapping mode. At the beginning, an operator adjusts the piezo-drive of the probe to its resonant frequency and chooses initial amphtude (Aq) and set-point amplitude (Ajp). The latter is... 

Since the first AFM applications, researchers have examined so-called force curves. In the contact mode, these are deflection-versus-distance (DvZ) curves, as seen in Figure 20.2a. Initially, DvZ curves were employed to check whether a particular deflection set point used for imaging corresponds to a net repulsive or net attractive force [25]. This curve can also be obtained in tapping mode... 

Zhong, Q., Innis, D., Kjoller, K., and Elings, V., Fractured polymer/silica fiber surface studied by tapping mode atomic force microscopy. Surf. Sci. Lett., 290, 688, 1993. 

Cleveland, J.P., Anczykowski, B., Schmid, A.E., and Elings, V.B., Energy dissipation in tapping-mode atomic force microscopy, Appl. Phys. Lett., 12, 2613, 1998. 

Ebenstein, Y., Nahum, E., and Banin, U., Tapping mode atomic force microscopy for nanoparticle sizing Tip-sample interaction effects, Nano Lett., 2, 945, 2002. 

Magonov, S.N., Elings, V., Cleveland, J., Denley, D., and Whangbo, M.-H., Tapping-mode atomic force microscopy study of the near-surface composition of a styrene-butadiene-styrene triblock copolymer film, Surf. Sci., 389, 201, 1997. 

FIGURE 21.12 Tapping-mode topographic image of uniaxially elongated NR vulcanizate. The elongation ratio was about 4. The scan size was 20 p,m. 

FIGURE 21.20 Tapping-mode atomic force microscopic (AFM) height image left) and phase image right) of NRIO sample. The stmctures indicated hy circles are considered to he carhon hlack (CB) fillers. 

---