X-ray diffraction measurements showed that a large number of vacancies were incorporated into thin Cu films grown on Cu(001) at low temperatures. For deposition at between 110 and 160K, the vacancy concentration, Cv, obtained from reflectivity data, did not change with the coverage, θ, for θ = 2.5ML to 20ML. However, Cv was temperature dependent: for 15ML-thick films, grown at different temperatures, it monotonically decreased with increasing T from Cv ≈ 2% at 110K to zero at T = 160K. A different Cv versus T dependence was observed for films grown at 110K and then annealed at progressively higher temperatures. Here Cv ≈ 2% persisted over a broad temperature interval (between 110 and 200K) and Cv exhibited a slower decrease upon heating, reaching zero at 300K.

Temperature-Dependent Vacancy Formation during the Growth of Cu on Cu(001). C.E.Botez, P.F.Miceli, P.W.Stephens: Physical Review B, 2002, 66[19], 195413 (6pp)