A. Carlsson et al., OBSERVATION OF STRUCTURE CHANGES FOR LI CU(111) BY PHOTOEMISSION FROMLI CORE AND QUANTUM-WELL STATES/, Physical review. B, Condensed matter, 57(20), 1998, pp. 13192-13198
Via photoemission from discrete quantum-well valence states and the Li
1s core level, three different types of atom rearrangements are obser
ved for Cu(111)/Li. In the monolayer coverage range gradual energy shi
fts for the core-level as well as a quantum-well state reflect a gradu
al lateral compression of the Li overlayer as more atoms are adsorbed.
The onset of Li substitution and formation of a (2x2) structure when,
at RT, monolayer Li coverage is exceeded, is monitored via the disapp
earance and appearance of quantum-well states characteristic of the ad
sorbed full monolayer of Li and the part substitutional (2x2) structur
e. respectively. A splitting of the Li Is emission peak into a doublet
reflects the two different Li sites characteristic of the (2x2) phase
. A small energy shift of the quantum-well state (25 meV) indicates th
at, if it is cooled (170 K), the substitutional structure is unstable
with respect to Li adsorption.