ANOMALOUS DIFFRACTION EFFECT ON THE SURFACE CORE-LEVEL PHOTOEMISSION FROM SI(001)2X1-CS SURFACE

The angular dependence of the Si 2p photoelectron intensity has been m easured for a Cs-saturated Si(001)2 x 1 surface. A surface Si 2p compo nent, which is attributed to the Si-dimer underneath the Cs overlayer, shows a large intensity variation as a function of azimuthal angle. T his denies the asymmetrical Si-dimer model proposed recently [Y.-C. Ch ao, L.S.O. Johansson, R.I.G, Uhrberg, Phys. Rev. B 54 (1996) 5901] on the basis of photoemission intensity of the surface Si 2p component. T he present result shows that the effect of photoelectron diffraction m ust be taken into account when discussing the origin of a surface comp onent from a seemingly angle-integrated photoemission intensity of the surface component. (C) 1998 Elsevier Science B.V.