HYDROGEN-INDUCED DERELAXATION ON A MBE GROWN GAAS(110) SURFACE

Up to now only indirect evidences of hydrogen induced derelaxation of the GaAs(110) surface have been obtained. In order to gain direct information on the surface structure MBE prepared GaAs(110) surfaces have been studied after H chemisorption (approximately 1 monolayer) by means of grazing incidence X-ray diffraction (GIXD). Because of the weak interaction of X-rays with H the effect of the hydrogenation can only be addressed through the modifications induced in the GaAs outermost layer. In the absence of surface reconstruction, the information on the in-plane displacements of the Ga and As surface atoms has been derived from integer order peaks at DELTAq(z) almost-equal-to 0. Assuming a constant bond length between surface and bulk atoms, an estimate of the normal atomic coordinates could also be obtained. The main result is a change in the surface structure after hydrogen chemisorption corresponding to a derelaxation of the hydrogenated GaAs(110) surface.