Low-energy electron diffraction from close-packed Na

The authors obtain a homogeneously thick film of close-packed Na with close-packed planes parallel to the surface by evaporating Na onto Cu(111) held at LN 2 temperature. Comparison between measured LEED intensity spectra, recorded at LN 2 temperature, and theoretical ones, calculated under the assumption that the crystal structure of Na is FCC or HCP, favours the HCP structure. The authors UPS results indicate that if Na is evaporated onto Cu(111) held at RT, it will form three-dimensional clusters on top of a Na film only few atomic layers thick.