Production of the two-dimensional submonolayer Gd silicides on the W(0 0 1) plane: A field emission study

Ultrathin films of the Gd silicides of various stoichiometries on the W(0 0 1) plane have been produced by annealing of Si and Gd coverages over a wide temperature range. The dynamics of the Gd silicide formation was checked via work function (ϕ) measurements. The work is constant over a wide temperature range ΔT (ΔT ∼ 900 K), suggesting the formation of a compound which was identified as Gd silicide. Three stoichiometric types of the two-dimensional submonolayer Gd silicides were found: a Gd-rich silicide with ϕ = 3.55 eV, the monosilicide with ϕ = 3.90 eV and a Si-rich silicide with ϕ = 4.40 eV. Changes in the Fowler–Nordheim preexponential term A also reflect the transition from the adsorbed layer to the formation of the Gd silicide.