FORMATION OF AN ORDERED SURFACE COMPOUND CONSISTING OF AG, SI, AND H ON SI(001)

With scanning tunneling microscopy and low energy electron diffraction , we have studied formation of a surface compound with Ag, Si and H on Si(001). In contrast to the case of Si(111)-(root 3 x root 3)Ag, on w hich adsorption of H atoms brings no homogeneous phases, moderate H ad sorption on Si(001)-(2 X 3) Ag produces a uniform compound phase with a 2 X 2 structure that lacks mirror symmetry in the [1 (1) over bar 0] direction. Further H adsorption causes agglomeration of surface atoms while the flat area of the surface becomes dominated by another asymm etric 2 X 2 structure. (C) 1998 Elsevier Science B.V. All rights reser ved.