ORDERING OF SULFUR INTERLAYER IN MOLECULAR-BEAM EPITAXY-GROWN SRF2, S/GAAS(111)A AND SRF2,/S/GAAS(111)B/

SrF2 films are epitaxially grown on sulfur-passivated GaAs(111)A and G aAs(111)B at a substrate temperature of 430 degrees C. The epitaxial r elations of these SrF2/S/GaAs{111} systems are type A. The position an d the ordering degree of sulfur interlayer were investigated by soft X -ray standing-wave (soft-XSW) triangulation studies. By the SrF2 epita xial growth, the ordering degrees of the sulfur interlayer are reduced . The in-plane distribution of the sulfur interlayer is more disordere d than the surface normal one, indicating that sulfur atoms buried und er the SrF2 epitaxial layers grown at 430 degrees C do not homogeneous ly occupy identical in-plane sites.