Direct Measurement of Valence-Charge Asymmetry by X-Ray Standing Waves
Joseph C. Woicik, E Nelson, P Pianetta
By detecting valence-photoelectron under condition of strong x-ray Bragg reflection, we have determined that a majority of GaAs valence charge resides on the anion sites of this heteropolar crystal, in quantitative agreement with the Ga-As bond polarity as calculated from the Hartree-Fock term values. In contrast, the valence charge distribution in GE is found to be symmetric. In both cases, the valence emission is found to be closely coupled to the atomic cores.