Jump-to-contact

A jump to contact transfer of Al from the scanning tip to the growing Al was observed (picture from [65] - with permission of the Peep owner societes). 

A conceptually different approach to nanostructuring electrode surfaces by tipgenerated metal clusters is sketched in Figure 5.15h. This approach, which facilitates a so-called jump-to-contact between tip and substrate for generating metal clusters, has been developed by our group and will be described in more detail in Section 5.4.3. 

Most of the work on nanostructuring electrode surfaces, which can be found in the literature, deals with the deposition of small metal clusters at predetermined positions. Over the years, we have developed a technique that is based on the jump-to-contact between tip and substrate [89] (Figure 5.15h) and that allows the formation of metal clusters in quick succession and without destroying the single crystallinity of the substrate. The principle behind this method is sketched in Figure 5.19 [90, 92] By applying an electrode potential to the STM tip that is slightly... 

Figure 5.19 Schematic diagram for continuous cluster generation by the tip of an STM via jump-to-contact.

Transfer of the electrochemically deposited metal from the STM tip to the substrate. This transfer (known as jump to contact) consists of two steps ... 

Figure 5.10d illustrates a case of contact mode. The contact position (z) is on the repulsive side of the short-range force curve. The arrow pointed to the left on Figure 5.10d represents the phenomenon of tip jump-to-contact with the sample caused by cantilever elastic bending when... 

Harrison et al. have considered indentation of nonmetallic systems including hydrogen terminated diamond [12,160]. Unlike the metal metal systems, diamond diamond systems did not show a pronounced jump to contact. This is... 

Kolb s group presented a jump-to-contact technique by which the surface can be decorated with small metal clusters provided there is sufficient interaction between a sample and a tip, the effect discussed earlier. By means of this technique, they showed the way to generate different patterns on a different scale. On the nanometer scale they presented the structure made of 12-Cu clusters of 0.8-mn height (see Fig. 29). They reported an interesting observation on the surprising stability against anodic dissolution of the fabricated clusters, and they proposed to explain this effect by quantum confinement of the electrons in the clusters that leads to an energy gap between the electronic states of the clusters. ... 

Figure 9.23 Force curve on wood surface illustrating the points where jump-to-contact (JTC) (approach) and jump-off-contact (JOC) (withdrawal) occur and the maximum values of the attractive force (pull-on force and pull-off force)...

In the spectroscopy mode of AFM force-distance curves F(z) are recorded at one or more scan points after the z piezo has been adjusted to the force setpoint (contact mode). The classical shape, as illustrated in Section 5.3.4 and Figure 63, is obtained mostly with hard materials or simpler molecules. In air a meniscus of water is formed at the jump-to-contact. Due to the meniscus force the jump-to- and jump-oflf-contact separations differ largely and the area of the hysteresis loop becomes quite large. Force-distance curves can have various appearances. An overview is given in Reference [233]. Spectroscopy is rarely employed in the dynamic mode because with an oscillating probe the tip-sample separation is never well-defined. On the other hand the snap-on is avoided and the complete interaction potential can be inferred from the measured frequency versus distance curve employing simulations [234,235]. 

Fig. 3.22. Force (a) and refractive index (b) in a hybrid cell, (a) Forces complete compression (filled symbols) and decompression (open symbols) cycles for two successive runs (circle and triangles). Notice the weak repulsion, the jump)-to-contact and jump-out from the strong adhesion at contact, (b) Index the birefringence is only a fraction of the full birefringence of the nematic and is constant. Gray regions correspond to instability in the interferometric equations.

The repulsive curves measured upon approach to EG3-OMe on gold showed some variabihty with respect to the range of interachon. Some of them were purely repulsive, while occasionally a jump-to-contact at distances of 5 nm before contact appeared. Whenever a jump-to-contact occurred, this was accompanied by a hysteresis in the loading—unloading cycle, while no hysteresis was found in the purely repulsive curves. This variability of the SFM data in terms of the range of the forces and the presence of an adhesion hysteresis might be atiributed to the structural inhomogeneity of the monolayers, i.e., the presence of different leases with dissimilar mechanical properties in the EG3-OMe layer. 

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