Effect of adsorption of electronegative and electropositive elements on the surface optical anisotropy of GaAs(001)
Surface optical anisotropy of GaAs(001) is extremely sensitive to adsorption of electropositive and electronegative atoms. The oxygen-induced experimental changes of the reflectance anisotropy spectrum of the As-rich surface are interpreted using ab initio calculations. We conclude that oxygen adsorption, contrary to previous beliefs, does not quench all surface-related optical transitions, but only those for which the initial state is surface-related. Alkali metal (AM) adsorption is found to induce a strong negative signal in the 3.5 eV-5 eV range, weakly dependent on surface reconstruction and AM nature, whose origin is discussed. © 2003 WILEY-VCH Verlag GmbH & Co. KGaA.