Quantum-well states in thin Ag films grown on the Ga/Si(111)- 3×3 surface

Silver thin films have been created by room temperature deposition on a Ga/Si(111)-$\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$ surface and their valence band structures and core levels have been measured by angle-resolved photoelectron spectroscopy (ARPES). Discrete quantum-well states (QWSs) quantized from the Ag $sp$ valence band are observed already at 3 monolayers (ML). The characteristics of the QWSs have been examined in the phase accumulation model for thicknesses between 3 and 12 ML. The phase shift and QWSs binding energies dependence with Ag film thicknesses have all been consistently derived. In-plane energy dispersion follows a parabolic curve, and the effective mass of the QWSs shows an increasing trend with binding energies as well as with reduced film thicknesses. Furthermore, the ARPES measurements reveal umklapp mediated QWSs around the $\overline{M}$ points of the Si(111) $1\ifmmode\times\else\texttimes\fi{}1$ surface Brillouin zone. The study confirms that the Ga/Si(111)-$\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$ surface is a good substrate for growing uniform ultrathin Ag films in room temperature conditions.