Microelectrochemical equipment

For all microelectrochemical experiments a metallurgical microscope was used. The sample was mounted on the microscope stage and the electrochemiqal microcell was fixed at the revolving nosepiece like an ordinary objective. This set-up enabled selection of an interesting area before the measurement and allowed a visible control of the investigated area after the measurement. The electrochemical microcell basically consisted of a glass microelectrode with the tip grounded (tip diameter = 2-1000 pm). As a seal a layer of silicone rubber is used for the front end. Such microcells lasted for about 50-100 experiments (Fig. 3).

potentiostat d = 2 pm-1000 pm

Fig. 3. Experimental set-up and electrochemical microcell.

potentiostat d = 2 pm-1000 pm

Fig. 3. Experimental set-up and electrochemical microcell.

In order to perform electrochemical measurements in the micrometer range, with currents ranging from 10"12 to 10"15 a several precautions were necessary. Besides good shielding to suppress electromagnetic interferences, a specially modified battery-operated high-resolution potentiostat (Jaissle 1002T-NC-3) was used. Additionally,the remaining noise of the measured output signal had to be reduced further by a homemade filter. This technique, which a current resolution of <10 fA, enabled the detection of processes in the micrometer range [7, 8].

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