Surface structure of Cu(100)-c(2 x 2)-Na: A LEED analysis

The surface structure of the Cu(100)-c(2X2)-Na phase formed by adsorption o f one-half monolayer Na on Cu(100) has been determined by quantitative anal ysis of low-energy electron diffraction (LEED) measurements. Na atoms occup y fourfold hollow sites on an essentially unperturbed substrate for adsorpt ion at both 100 and 300 K. The vertical distance between the Na layer and t he first Cu layer is determined to be 2.37 +/-0.04 Angstrom at 100 K and 2. 42+/-0.04 Angstrom at 300 K. An analysis of LEED intensities measured for t he clean Gu(100) surface confirms previous reports of a small contraction o f the first layer spacing, but does not show an expansion of the second-lay er spacing as found in medium energy ion scattering studies and in a previo us LEED study. Bulls. Debye temperatures found in this study are in remarka bly good agreement with previous x-ray studies. [S0163-1829(99)01427-7].