Atomic force microscopy contact scanning mode

A number of methods are available for the characterization and examination of SAMs as well as for the observation of the reactions with the immobilized biomolecules. Only some of these methods are mentioned briefly here. These include surface plasmon resonance (SPR) [46], quartz crystal microbalance (QCM) [47,48], ellipsometry [12,49], contact angle measurement [50], infrared spectroscopy (FT-IR) [51,52], Raman spectroscopy [53], scanning tunneling microscopy (STM) [54], atomic force microscopy (AFM) [55,56], sum frequency spectroscopy. X-ray photoelectron spectroscopy (XPS) [57, 58], surface acoustic wave and acoustic plate mode devices, confocal imaging and optical microscopy, low-angle X-ray reflectometry, electrochemical methods [59] and Raster electron microscopy [60]. 

Although the resolution of atomic force microscopy (AFM) is basically inferior to that of STM, the technique has the advantage that insulating materials can also be used as substrates. In AFM the forces acting between the tip and the sample surface are detected. The probe tip mounted on a flexible cantilever scans over the sample. AFM can be operated in contact mode, exploiting repulsive forces, as well as in non-contact mode, exploiting attractive forces. In the contact mode the probe tip is in direct contact with the sample surface (Fig. 7.8). Either the tip is passed over the sample surface at constant height (CHM,... 

The topology of the microstructure was investigated by atomic force microscopy (DualScope/DME, Herlev, Denmark) in non-contacting mode. The scan speed of the cantilever was set to 50 xm/s at a constant force of0.16nN. 

Atomic force microscopy (AFM) allows the topography of a sample to be scanned by using a very small tip made from silicon nitride. The tip is attached to a cantilever that is characterised by its spring constant, resonance frequency, and a quality factor. The sample rests on a piezoceramic tube which can be moved horizontally x,y motion) and vertically (z motion). Displacement of the cantilever is measured by the position of a laser beam reflected from the mirrored surface on the top side of the cantilever, whereby the reflected laser beam is detected by a photodetector. AFM can be operated in either contact or a noncontact mode. In contact mode the tip travels in close contact with the surface, whereas in noncontact mode the tip hovers 5-10 nm above the surface. 

Atomic Force Microscopy (AFM). AFM measurements were performed with a commercial scanning probe microscope (Nanoscope III, Digital Instruments, Santa Barbara, CA). Measurements of surface topography and lateral force were made simultaneously by operating the instrument in contact mode while scanning the cantilever laterally. All measurements were performed in ambient air on freshly plasma cleaned samples. 

Atomic force microscopy (AFM) is the most commonly nsed scanning probe microscopy (SPM) technique. It has been demonstrated to be an invaln-able technique for characterization of nanoscale snrface strnctures. In this method, the deflection of a cantilever due to repulsive electronic interactions of an attached sharp tip with the surface is measured. The microscopic movement of the tip creates a force that is measnred to provide an image of the surface. Both contact and tapping mode AFMs have been employed for the investigation of surface topography, the latter avoiding contact of the tip with the surface, which can be a problem if the material is soft. 

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