Resolution atomic force microscope

Muller D W, Fotiadis D and Engel A 1998 Mapping flexible protein domains at subnanometre resolution with the atomic force microscope FEBS Lett. 430 105... 

Manne S, Flansma P K, Massie J, Elings V B and Gewirth A A 1991 Atomic-resolution electrochemistry with the atomic force microscope copper deposition on gold Science 251 183... 

The atomic force microscope (ATM) provides one approach to the measurement of friction in well defined systems. The ATM allows measurement of friction between a surface and a tip with a radius of the order of 5-10 nm figure C2.9.3 a)). It is the tme realization of a single asperity contact with a flat surface which, in its ultimate fonn, would measure friction between a single atom and a surface. The ATM allows friction measurements on surfaces that are well defined in tenns of both composition and stmcture. It is limited by the fact that the characteristics of the tip itself are often poorly understood. It is very difficult to detennine the radius, stmcture and composition of the tip however, these limitations are being resolved. The AFM has already allowed the spatial resolution of friction forces that exlribit atomic periodicity and chemical specificity [3, K), 13]. 

A very similar technique is atomic force microscope (AFM) [38] where the force between the tip and the surface is measured. The interaction is usually much less localized and the lateral resolution with polymers is mostly of the order of 0.5 nm or worse. In some cases of polymer crystals atomic resolution is reported [39], The big advantage for polymers is, however, that non-conducting surfaces can be investigated. Chemical recognition by the use of specific tips is possible and by dynamic techniques a distinction between forces of different types (van der Waals, electrostatic, magnetic etc.) can be made. The resolution of AFM does not, at this moment, reach the atomic resolution of STM and, in particular, defects and localized structures on the atomic scale are difficult to see by AFM. The technique, however, will be developed further and one can expect a large potential for polymer applications. 

Atomic force microscope (AFM) is a powerful nanotechnology tool for molecular imaging and manipulations. One major factor limiting resolution in AFM to observe individual biomolecules such as DNA is the low sharpness of the AFM tip that scans the sample. Nanoscale 1,3,5,7-tetrasubstituted adamantane is found to serve as the molecular tip for AFM and may also find application in chemically well-defined objects for calibration of commercial AFM tips [113]. 

Albrecht, T. R., and Quate, C. F. (1988). Atomic resolution with the atomic force microscope on conductors and nonconductors. J. Vac. Sci. Technol. A 6,... 

Manne, S., Hansma, P. K., Massie, J., Elings, V. B., and Gewirth, A. A. (1991a). Atomic-resolution electrochemistry with the atomic force microscope - Copper deposited on gold. Science, 251, 183-186. 

The field ion microscope is perhaps the simplest of all atomic resolution microscopes as far as mechanical and electrical designs are concerned. The atomic resolution microscopes, at the present time, include also different types of electron microscopes,1 the scanning tunneling microscope (STM)2 and the atomic force microscope (AFM)2 Before we discuss the general design features of the field ion microscope it is perhaps worthwhile to describe the first field ion microscope,3 and a very simple FIM4 which can be constructed in almost any laboratory. The first field ion microscope, shown in Fig. 3.1, is essentially a field emission microscope5 except that it is now equipped with a palladium tube with... 

When the first edition was published in 1992, the resolution of the acoustic microscope techniques used at the time was controlled by the wavelength. In practice the frequency-dependent attenuation of the acoustic wave in the coupling fluid sets a lower limit to the wavelength, and therefore to the resolution, of about 1 pm for routine applications. Since then scanning probe techniques with nanometre scale resolution have been developed along the lines of the atomic force microscope. This has resulted in the development of the ultrasonic force microscopy techniques, in which the sample is excited by... 

In atomic force microscopy (AFM), the sharp tip of a microscopic probe attached to a flexible cantilever is drawn across an uneven surface such as a membrane (Fig. 1). Electrostatic and van der Waals interactions between the tip and the sample produce a force that moves the probe up and down (in the z dimension) as it encounters hills and valleys in the sample. A laser beam reflected from the cantilever detects motions of as little as 1 A. In one type of atomic force microscope, the force on the probe is held constant (relative to a standard force, on the order of piconewtons) by a feedback circuit that causes the platform holding the sample to rise or fall to keep the force constant. A series of scans in the x and y dimensions (the plane of the membrane) yields a three-dimensional contour map of the surface with resolution near the atomic scale—0.1 nm in the vertical dimension, 0.5 to 1.0 nm in the lateral dimensions. The membrane rafts shown in Figure ll-20b were visualized by this technique. 

The resolution of the atomic force microscope depends on the radius of curvature of the tip and its chemical condition. Solid crystal surfaces can often be imaged with atomic resolution. At this point, however, we need to specify what Atomic resolution is. Periodicities of atomic spacing are, in fact, reproduced. To resolve atomic defects is much more difficult and usually it is not achieved with the atomic force microscope. When it comes to steps and defects the scanning tunneling microscope has a higher resolution. On soft, deformable samples, e.g. on many biological materials, the resolution is reduced due to mechanical deformation. Practically, a real resolution of a few nm is achieved. 

To achieve high resolution with an atomic force microscope it is necessary to focus only on the short range forces. In Fig. 5 the distance dependence of the tunneling current and a short range force (modeled by a gradient of a Morse potential) is compared. 

A "direct" observation of individual atoms is achieved in atomic resolution transmission electron microscopes (AR-TEM), in the scanning tunneling microscope (STM), and in the atomic force microscope (AFM) (5, 4). While AR-TEM are large machines with very high voltage (6 x 105 to 106 volts) applied to an electron-transparent small object, STM and AFM are small devices with ultrasensitive tip positioning mechanics that is suited for flat or near-flat objects and will... 

Binnig, G., Gerber, C., Stoll, E., Albrecht, T.R., and Quate, C.F. (1987). Atomic resolution with atomic force microscope. Europhys. Lett., 3(12) 1281 1286. 

---