Lateral interactions and structural phase transitions in ultrathin Hg films

We have investigated the energetics and lateral interactions of ordered mercury overlayers on Cu(100) and Ag(100) by thermal desorption spectroscopy (TDS). We find evidence for the coexistence of phases on Cu(100) from thermal desorption spectroscopy. Hg adsorbs on both Cu(100) and Ag(100) with a coverage-independent sticking coefficient indicative of a mobile precursor state. Hg on Cu(100) is observed to have a barrier to desorption consistent with the existence of a precursor state. The two equilibrium phases of Hg on Cu(100) have zero coverage heats of desorption of 0.74 eV (c(2×2)) and 0.70 eV (c(4×4)) with pairwise attractive interactions of 0.21 and 0.13 eV, respectively. The ordered 1×1 phase of Hg on Ag(100) has a zero coverage heat of desorption of 0.63 eV with pairwise repulsive interactions of 0.38 eV.