Photoemission and LEED investigation of the initial growth of Cr on Ag(001)

The initial growth of Cr on a Ag(001) surface is studied by low energy electron diffraction (LEED), angle resolved ultra-violet photoemission and X-ray photoelectron diffraction, as a function of deposition temperature. At 100 K, the LEED diagram is p(1 x 1) and a highly defected monolayer is initially formed. When the substrate is kept at room temperature during Cr evaporation, the LEED pattern is still p(1 x 1), and multilayer growth with markedly improved atomic order and accompanied by Ag segregation occurs. In contrast, at 430 K, a weak c(2 x 2) LEED diagram is obtained at low electron energies (<85 eV), attributed to the presence of well ordered bare Cr monolayer islands with p(1 x 1) atomic order but presenting a c(2 x 2) antiferromagnetic superstructure. This superstructure is identical in every respect to the one identified in our earlier work [Phys. Rev. B 44 (1991) 8407] and quite similar to the magnetic c(2 x 2) Mn monolayer on Ag(001) investigated recently by dynamical LEED [Phys. Rev. B 62 (2000) 2944]. Valence band data indicate coexistence of monolayer c(2 x 2) Cr domains and multilayer patches made of p(I x 1) Ag islands on top of a mixed Cr Ag phase. (C) 2002 Elsevier Science B.V. All rights reserved.