Surface core-level shifts for chlorine covered GaAs (1 1 0) surfaces

Photoemission measurements show that upon chlorine adsorption the Ga 3d surface core-level remains essentially unchanged whereas the As 3d level is shifted by 820 meV to higher binding energy changing the sign of the shift with respect to the bulk level. Chlorine is thus bound to As in a single chemisorption state. The shift is due to charge transfer. The adsorption does not change the surface relaxation.