Electron spectroscopy study of the growth of Mo on Al at low temperature: Relevance for cluster physics

A spectroscopic investigation of the initial overgrowth of Mo (up to 8 × ${10}^{15}$ atoms/${\mathrm{cm}}^2$) onto Al at low temperature (Å80 K) is presented. Angle-integrated valence photoemission ($h\nu =21.2\mathrm{}$ eV), $\mathrm{Mo} 3d$, $\mathrm{Al} 2p$ x-ray photoemission spectroscopy ($h\nu =1253.6\mathrm{}$ eV), and Mo $\mathrm{MNV}$ and Al $\mathrm{LVV}$ results are reported. The overgrowth takes place with the formation of islands whose valence states strongly support recent calculations for small bcc clusters of refractory metals. Significant differences with respect to bulk metals are attributed to surface $d$ states.