The adsorption of Li and Cs on CdTe(100) single crystals was investiga
ted using different surface sensitive electron spectroscopies. Low-ene
rgy electron diffraction shows a number of surface reconstructions of
the clean surfaces, influenced by the Cd/Te ratio. Deposition of Li sh
ows a constant sticking probability, while Cs has a variable sticking
probability, characteristic of island growth coalescing at a coverage
of a monolayer. Li and Cs both form amorphous monoatomic layers. Large
work-function changes of the CdTe surface as a function of Li and of
Cs coverage were found at the initial stages of adsorption, indicating
that Cs and Li atoms are to a large extent ionized on the surface (10
0) plane. The initial dipole moments for Cs and for Li were calculated
with the Helmholtz equation mu(Cs,theta-->0)approximate to 26 D and m
u(Li,theta-->0)approximate to 3.2 D and using Topping plots mu(0,Cs)=1
27.2 D and mu(0,Li)=4.22 D. Adsorption of oxygen on the cesium-covered
surface raises the work function by Delta phi=0.5+/-0.05 eV. Reflecti
on-electron energy-loss spectra of the cesiated CdTe(100) surface at E
(p)=100 eV, recorded at a low temperature (96 K), show a characteristi
c Cs two-dimensional surface plasmon, HBAR omega(s) at 2.05 eV, which
disappears with rising temperature. During Cs growth a loss is observe
d at 26.6 eV which is assigned to Cs 5s core-level transitions.