Self-Organized Nanocavity Arrays on Pt/Ge(001)

We report on the formation of well-ordered arrays of nanometer-sized cavities on a Pt-modified Ge(001) surface. The nanocavities are thermodynamically stable and form ordered domains separated by antiphase boundaries. When imaged at negative sample bias, the nanocavities exhibit an elliptical shape, whereas they appear as rectangular cavities at positive sample bias. A well-defined electronic state at 0.7 eV above the Fermi level is found. Spatial maps of the differential conductivity reveal that this electronic state is located at the regions between neighboring nanocavities in the well-ordered arrays. These arrays of nanocavities can serve as a template to study single molecules or molecular assemblies for future molecular electronics applications.