Troubleshooting

The problems and their potential solutions listed below are common to both Electrochemical (EC) STM and EC AFM.

General Considerations

Improper Electrical Connections

Poor or improper electrical connections between various elements of the EC SPM will cause malfunctions. Check all electrical connections and settings whenever a problem arises which might have its root in the electrical wiring and switches.

Connections include those between:

• Potentiostat/Galvanostat and EC Chuck.
• Electrodes and spring terminals

EC-Specific Problems

Unexpected Peaks in Voltammogram

The presence of impurities and contaminants in the fluid cell can have a strongly detrimental effect on EC SPM. In AFM studies, where the fluid cell allows for electrolyte circulation through the tubing, the cleanliness of the tubes and the syringes is just as important as that of the elements of the fluid cell. The presence of contaminants can lead to unexpected peaks in the voltammogram.

Excessive Deposition of Solids on Sample

If not monitored well, continuous cathodic currents may deposit a thick layer of solid on the sample. If the deposition rate is high enough, the deposited layer may become so thick that the Z-piezo retracts to its limit. The feedback mechanism and the Z-piezo can then no longer compensate for further growth of the deposited layer, and the SPM probe is pushed into the sample.

In such cases the Z-center position indicator on the image monitor drifts up, indicating that the piezo is retracting. If not compensated for, the Z-center position indicator drifts all the way to the top of its range, and the word “limit” appears in red letters next to it. If this happens, use the Motor > Step motor > Tip up commands to raise the probe, thus bringing the Z-center position close to center (0 V). Damage to an AFM tip is possible.

Deposition Not Imaged by SPM Probe

Sometimes the voltammogram indicates reduction taking place, but nothing is deposited where the SPM probe is scanning. There are several possible explanations for this phenomenon:

• The most common explanation is that most of the deposition on the sample is taking place near the counter electrode and away from the SPM probe. Another possible cause is the tip-shielding effect. Using a ring-shaped counter electrode promotes uniform reactions.
• In AFM operation: Reduced species may be present in the scan area but are so loosely bound to the sample surface that the AFM probe force is great enough to push the material aside.

Voltammogram Shows Jumps in Cell Current

First check that all electrodes are making contact with the electrolyte in the cell.

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