56 Experimental Methods
Figure 3.9: Schematic showing the SEM process and signals generated. The incident
electron beam is focused down onto the sample, whereby a variety of signals
are generated. Some of these are shown on the gure, including secondary electrons,
backscattered electrons, Auger electrons and characteristic X-rays. The amount of secondary
electrons that are able to escape the surface depends on the curvature around
the beam spot and interaction volume, which give rise to contrast and topography
information.
also cause secondary electrons which aect the resolution achieved in secondary
electron imaging. The SEM images included in this thesis are all acquired by
secondary electron detection.
3.3 Electrochemical measurements
The results in this thesis are centered around the electrochemical properties of
thin lms. Therefore, emphasis has been put on developing protocols and measurement
procedures. In general, electrochemical measurements deals with the
response of electrodes immersed in an electrolyte under the inuence of applied
potentials or induced currents. Specically for this project we are interested in
the response of a single electrode in a certain potential range, where the oxygen
evolution reaction occurs. For this purpose a three electrode setup has been
employed. An image of such a setup can be seen in gure 3.10.
The three electrodes used are: a working electrode, a counter electrode and a
reference electrode. The working electrode contains the sample which response
or activity is measured. Current ows between the working and the counter
electrode when a suitable potential dierence is applied. In the case of oxygen
evolution on the working electrode (working as anode) the counter electrode will