Etched electrodes

The data available up to 1971 have been collected by Carr et al.,m who have also reported apzc value of -0.59 0.02 V (SCE) for a melted, cut, mechanically polished, and finally electrochemically and chemically etched electrode. 

In Figure 2 we show the equivalent results with a reasonably effective stabilizing agent, ferrocyanide, present. In this figure we show results with HF present (no oxide) for comparison as curve (d). The first cycle of a freshly etched electrode in the 0,1 M potassium ferrocyanide/water solution is indicated in the current/voltage characteristics as curve (a). Now in curve... 

Although disk-shaped tips are typically most useful for SECM experiments, it is not always possible to produce such tips, especially when they have to be nanometer sized. For some special applications (e.g., penetration experiments), one may want to purposely fabricate tips with different geometries. To characterize nondisk shaped tips, experimental approach curves were obtained and then compared to simulated ones [12]. A number of UME tip geometries including hemispheres [14, 15], spheres [16], rings [17], ring-disks [18], and etched electrodes [19, 33] have been characterized in this way. 

FIGURE 6.22. Current-time transients at -2.0V on /j-Si(lOO) in 2M KOH at 45°C measured for an oxide-free chemically etching electrode when 3mM ferricyanide was added to the solution at t = 0 measured after anodic oxidation at 0.0 V when, at t = 0, the potential was stepped back to -2.0 V in a solution containing 3mM ferricyanide. (Reprinted from Bressers et 1995, with permission from Elsevier Science.)... 

It should be pointed out that, for some electrodes, chemical etching is not sufficient to obtain the optimal surface roughness for SERS, as shown in Fig. 16. One may consider further SERS activation to chemically etched electrodes by ORC, either in the chemical etching solution (ex situ) or in the measured solution (in situ). However, the electrode treated by the in situ ORC, in general, has the higher activity, but poorer stability, as the intensity deceases with time irreversibly. A detailed discussion of how to deal with this problem will be given in the Sect. 3.6.3.7.4 on Troubleshooting. 

Williams JEG, Millar J, Kruk ZL, A comparison of cut and spark-etched electrodes for fast cyclic voltammetry, Br J Pharmocol, 107, 1992. 

The capacity of the silver has been estimated both by Proskurnin and Frumkin and by Veselovsky For an etched electrode 7000 F/cm was found and even for a smooth electrode the minimum capacity (in 0 1 N KNOs) was 100 jx F/cm , suggesting either a pronounced roughness of the smooth electrode or contribution to the capacity of other phenomena than the formation of the double layer ... 

In situ resolution of the crystalline order has been achieved by Villegas et al.594 on Cu(100) electrodes purposely disordered by oxidation or ion bombardment. Ordering was achieved by chemical and electrochemical etching and confirmed by LEED, SEM, and STM. 

A boron-doped diamond electrode was used after wet etching. 

It was reported that high selectivity can be achieved with addition of small amount of O2, which increases the etch rate of metal electrode [4] while suppresses the etch rate of dielectrics [5]. Figure 2 shows the comparison of residues formation after etching between in (a) CI2 and (b) CI2/O2. Agglomerated residues were observed after etching in CI2/O2, indicating that addition of O2 (1%) enhances residues formation on the etched surface. 

Fig. 4. (a) TEM image of TaN metal electrode gate stack after Ch etching, revealing thick residues formation on the sidewall (etching was done in DPS) SEM image of TaN metal electrode (b) before and (c) after DHF cleaning. 

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