• Oxide supported metal particles with less than 100 atoms develop quantized electronic structure and gaps at the Fermi level
• Resulting quantum well states often compatible with simple particles-in-the-box-models

Linear Au-chains on alumina films

• Electron transfer from oxide support into ad-gold leads to growth of monatomic chains with pronounced standing wave patterns 
• Symmetry and energy of quantum well states reveals number of atoms and of transfer-electrons in the Au chains

Topographic images of Au chains on alumina (top) and corresponding quantum well states (middle: experiment, bottom: calculation)

For details: Counting transfer electrons through alumina films, Nilius et al., Phys. Rev. Lett. 100 (2008) 096802.

Planar Au-islands on MgO films

• Development of 2D Au-islands due to electron-transfer from the MgO film (0.2|e| per interface atom)
• Observation of quantum well states with increasing number of nodal planes (eigenstates of a parabolic potential)

HOMO, morphology and LUMO (left to right) of an 18-atom Au-island

For details: Quantum well states in two-dimensional gold clusters on MgO films, Lin et al., Phys. Rev. Lett. 102 (2009) 206801.