Structural features of CeO2(111) revealed by dynamic SFM

Abstract

Cerium dioxide is an insulating material that is important in various fieldsof catalysis and often used as an oxygen reservoir. The (111) surface ofCeO2 is catalytically active and we study this surface in its various oxidation states by dynamic forcemicroscopy, an analysis that may eventually help to establish structure–function relationshipsfor catalysis. We present highly resolved images and atomic details of surface features onCeO2(111) like terrace structures, step edges, kinks and hexagonally shaped pits that are naturallyformed during surface preparation by sputtering and annealing cycles. We find that suchstructures can be well imaged with atomic resolution and that they exhibit morphologicalcharacteristics that are significantly different in details from those of cleavedCaF2(111), a surface with exactly the same crystallographic structure and very similar latticeconstants and ionic radii. In this study, we continuously monitor the shape of the tip apexand demonstrate that high quality atomic resolution imaging is possible with one tip,although the tip apex is drastically changed by wear during 45 h of scanning.