Speaker
Description
We studied the dissociative adsorption of oxygen on the Cu(110)
surface using Photoelectron Emission Microscopy (PEEM) and Differential
Reflection Spectroscopy (DRS) simultaneously. Unlike many
experiments carried out already in the 1970s and 1980s, our approach
focusses on real-time monitoring. For oxygen exposures up to ∼100L,
at temperatures between 350K and 420K, the process saturates at an
oxygen coverage of 0.5 with a well-ordered (2×1)O superstructure. At
intermediate coverages, a regular pattern of alternating Cu and CuO
stripes is formed [1].
We used a PEEM with a xenon lamp (Xe) to study changes in the
electron yield (EY) during the exposure. Oxygen adsorption causes
a decrease in EY and, hence, an increase in the work function.
Since our DRS setup uses the same light source as the PEEM, we
can synchronously record the change of the reflectance and reliably
compare the two signals. Interestingly, the normalised adsorption
curves are not identical, indicating that the PEEM and/or the DRS
signals are not directly proportional to the oxygen coverage. This
could be related to the effect of the formation of the nanostructured
Cu-CuO stripe pattern upon oxygen adsorption [1].
[1] K. Kern et al., Phys. Rev. Lett. 67, 855 (1991).