Dynamic line-scan

Based on the presented typical substrate morphology shown in Fig. 1, the local progress of Pb adsorption has been systematically studied at the three morphologically different substrate domains, using a special dynamic line-scan technique described... 

If the time consumption is acceptable and the image drift is negligible, a scan line can be scanned twice to separate topography and electrical properties. In this case, a first scan in contact or better in a dynamic mode without an electrical excitation is performed. The tip is lifted and for the following second scan the z-piezo is controlled in a way that the tip follows the same topography as for the first scan (constant tip-sample distance or interleave scan). During this second line scan, one of the above-mentioned measurements of electrical properties can be performed [396]. 

The virtual transducer can be placed in a specific location on the test object surface, it can be moved along a path (e.g. a robot scanning path generated off-line or a path resulting from a real inspection sequence) or it can be moved along the surface, dynamically updating the ultrasonic sound propagation in the material. 

STM has not as yet proved to be easily applicable to the area of ultrafast surface phenomena. Nevertheless, some success has been achieved in the direct observation of dynamic processes with a larger timescale. Kitamura et al [23], using a high-temperature STM to scan single lines repeatedly and to display the results as a time-ver.sn.s-position pseudoimage, were able to follow the difflision of atomic-scale vacancies on a heated Si(OOl) surface in real time. They were able to show that vacancy diffusion proceeds exclusively in one dimension, along the dimer row. 

The data of heating rate and the temperature at which the maximum rate of reaction occurs, Tpeak, was plotted, and fitted to a linear model. The activation energy, E, of a silicone rubber was calculated with the data from four dynamic scanning rates. The slope of the line corresponds to the negative ratio of the activation energy and the universal gas constant R (8.3145 J/gmol/K) as can be seen in Fig. 7.20. 

Using an SFM-type microscope, measurements of electrical properties have to be performed either in contact mode, i.e. with the conductive SFM tip being in mechanical contact with the surface, or in non-contact mode, a dynamic mode with vibrating cantilever, or in the so-called lift mode, where a line is repeatedly scanned with a chosen and controllable tip-surface distance. Contrasts of capacitance, dielectric constants or potentials can be achieved both in the contact and in the non-contact mode, and the quality of the result is not influenced by the sensitivity of the chosen instrument alone. All the sample properties (most of all sample thickness and size) affect the sensitivity of both methods, so that the prediction of the most successful technique is not always possible. 

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