Conclusions

The AFM-based cantilever stress sensor is a highly sensitive device. We have used the sensor to obtain information about processes occurring at the solid/liquid interface in an electrochemical environment with submonolayer sensitivity. This work has shown the importance of lateral surface interactions in determining adlayer structures. In particular the repulsive charge-charge interactions, unique to the electrochemical environment, are clearly important in UPD and presumably in other surface electrochemical processes. These forces are predominantly responsible for the open adlattice structures which are frequently observed at this interface compared with the close-packed metal monolayers that are associated with the metal/vacuum interface. The extent to which these interactions are related to the co-adsorption of negatively charged ions requires further investigation for a variety of UPD systems.

As well as the sensitivity of this device, which could clearly be advantageous in more stringent sensor applications, the high resonant frequency of the cantilever means that it is ideally suited to applications where fast lever response is needed. In this work potential scan rates of several hundred mVs"1 shave been used. We have started studies of fast electrochemical processes using potential-step methods, since the fast dynamic response of the cantilever is its primary advantage over other stress sensors. Additionally one may ultimately expect a combined instrument so that the tip of a scanning tunneling microscope can be vised to image the sensor surface in-situ, allowing for real-space surface-strain imaging in addition to surface stress.

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