Tip artefact

Figure 6. Low-resolution STM survey image of a partly oxidized graphite flake. The asymmetric V-shape of the deep trenches is a tip artefact. Conditions Burleigh AR1S 6000, air, W tip, constant current mode, gap voltage 200 mV.

Fig. 2.43 Contact mode AFM and deflection images exhibiting a tip artefact...

Fig. 19 AFM images of G-wires freshly adsorbed onto mica imaged via tapping mode (a). Same sample imaged by the same tip 24 h later after drying in an oven at 37 °C (b). Low current scanning tunneling microscopy image of G-wires freshly adsorbed on mica (c). Note the preferential orientation is not a sample preparation artefact, e.g., due to rinsing [126]. Reprinted with permission...

The fluctuations of isolated steps have been studied, both theoretically - using Langevin theory, Monte Carlo simulations of SOS models, as well as exact methods, and experimentally by scanning tunneling microscopy (caution is needed in the measurements to avoid artefacts of tip assisted motions of the steps O-... 

On rough surfaces small values of may be easily explained by tunneling from the side of the tip. The presence of several mini-tips is a second problem, common to rough and flat surfaces. Both effects introduce artefacts in the determination of because the distance s is ambiguously defined in Eq. (3). To exclude such artefacts one should verify the resolution of the tip before and after measurements, and preferably perform measurements on flat portions of surfaces. 

One central concern with routine AFM on polymers is the presence of shear forces that occur in CM. These forces are a result of friction between AFM probe tip and the polymer sample and may deform and plastically modify the polymer surface. This has been observed even for glassy materials, such as PS, when imaged at ambient conditions (see Sect. 3.2.3 in Chap. 3 Fig. 3.16). In addition to sample damage, the tip may be affected by adhering particulates or, even worse, by wear. These phenomena limit the resolution dramatically and may result in unwanted artefacts (excessive tip imaging). Thus, minimized imaging forces are essential, and this may require the operation under a suitable liquid to eliminate capillary forces. 

Fig. 2.49 Overview on artefacts in TM-AFM (a) TM AFM height image of a scan during which the tip temporarily lost contact with the sample surface (setpoint free oscillation amplitude) panel (b) displays the bistability effect in intermittent contact mode AFM...

For all nc-AFM measurements, a Kelvin probe force microscopy (KPFM) feedback controller was additionally activated for simultaneous topographic imaging [19]. In order to compensate for electrically or electronically induced artefacts, an ac voltage was applied between tip and sample and used in combination with lock-in techniques and a feedback controller to compensate for the contact potential difference (CPD) between tip and sample. With this method, nc-AFM is assiued to image the sample topography without any artefacts originating from different local surface potentials [20]. 

The diermal conductivity contrast image obtained by scanning thermal microscopy represents a convolution of the true thermal transport properties of the specimen with artefacts arising from changing tip-sample thermal contact area caused by any surface roughness of the specimen [48]. When the probe encounters a depression on the surface, the area of contact between the tip and sample increases, resulting in increased heat flux from the tip to the sample. More power is required to maintain the tip temperature at the set-point value and... 

Figure 3.7 A tapping mode AFM image of plasmid DNA-polymer complexes (obtained using tapping mode in aqueous buffer) showing double tipping. The repeating features allow this type of imaging artefact to be easily recognized (image provided courtesy of 3.E. Ellis, University of...

Figure 11.9 Mapping of bond cleavage in self-reporting chemiluminescent elastomers that are toughened ty sacrificial bonds, (a) Bis(adamantyl)-1,2-dioxetane breaks under a mechanical force, resulting in chemiluminescence. (b) Intensity-coloured images of polymer networks during crack propagation of notched samples and schematic depiction of bond breaking around the crack tip. SN, DN, TN label elastomers of different molecular architecture ( single network , double network and triple network ). The dashed line indicates the perimeter of the sample. Vertical lines are artefacts of the detector.

The measurements are an artefact (Ling, 1969). Ling attributes the values obtained by Lev (1964) and Hinke (1959) to the damaged microenvironment about the ion electrode tips. We may estimate the time required for the ions to diffuse out of this microenvironment as follows. From Crank (1956) and Hinke (1973), the reflected diffusion from a layer of thickness (h) of a substance with initial concentration (Cq at t = 0) may be described as... 

Bogdanovic, G., Meurk, A. and Rutland, M., Tip friction - artefact and torsional spring constant determination, Colloid Surf., B, 19, 397-405 (2000). 

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