NUCLEATION AND GROWTH OF ULTRATHIN FE AND AU FILMS ON CU(100) STUDIED BY SCANNING TUNNELING MICROSCOPY

Cu(100) surfaces modified by depositing Au and Fe in the monolayer (ML) thickness regime are studied with the scanning tunneling microscope (STM). STM results confirm that Au deposition of 0.5 ML at 300 K creates a CuAu c(2X2) alloy monolayer, with nearly regular disruptions of structure that relieve misfit strain. The alloy forms by Au replacement of Cu atoms in the surface. Submonolayer Fe deposition at 300 K yields monolayer islands and additional features interpreted as Fe patches in the surface Cu layer. This suggests that Fe atoms replace Cu atoms in the surface. Deposition of approximately 4 ML Fe yields a more homogeneous surface with height variations that suggest structural disorder in the Fe layer. Fe deposition at approximately 110 K and warming to 300 K yields many monolayer and bilayer islands, with no evidence of Fe incorporation into the surface. Unusual tip behavior is also discussed which appears to yield STM sensitivity to the chemical difference between Fe and Cu areas.