Ng. Fazleev et al., STUDY OF POSITRON SURFACE-STATES ON THE ALKALI-METAL-COVERED TRANSITION-METAL SURFACE, Applied surface science, 85(1-4), 1995, pp. 26-32
Citations number
31
Categorie Soggetti
Physics, Condensed Matter","Chemistry Physical","Materials Science, Coatings & Films
We present a first-principles study of annihilation probabilities of s
urface trapped positrons with core electrons at the Cu(100) surface wi
th sub-monolayers of Cs adsorbed. Image-potential-induced positron sur
face states are calculated using a corrugated-mirror model in a full t
hree-dimensional geometry. These states are studied for various arrang
ements of Cs atoms below and above the critical alkali-metal coverage
of approximately 0.7 physical monolayer. Computer simulations of the d
eposition of Cs atoms are used to show that hexagonal close-packed Cs
islands are formed at about 0.7 physical monolayer coverage of Cs. It
is found that the abrupt decrease in the positron annihilation rate wi
th Cu 3p electrons observed experimentally results from a metallizatio
n of the Cs islands. This causes a shift in the localization of the po
sitron bound state from the Cs/Cu interface to the vacuum side of the
Cs overlayer, with the corresponding abrupt decrease in the positron a
nnihilation probability with Cu electrons. Annihilation probabilities
for positrons with Cs electrons are also computed and compared with ex
periment.