Effects of temperature on the oxygen aided Cr growth on Fe(001)

The morphology of ultra-thin Cr films deposited on Fe(001) substrates at two growth temperatures, namely 380 K and 570 K, with and without the presence of a surface oxygen layer, has been studied by means of scanning tunneling microscopy and X-ray photoemission spectroscopy. A direct comparison between the Cr growth mechanisms on the pristine Fe(001) surface and on the oxygen covered Fe-p(1 × 1)O surface illustrates the role of the oxygen action during the growth of the Cr films. In presence of oxygen, layer by layer growth takes place at the lower temperature thanks to the low Ehrlich-Schwoebel barrier for adatom descent at the islands edges. Epitaxial growth of Cr at the higher temperature is characterized by a reduced roughness at sub-monolayer coverages. When increasing the coverage, on the other hand, the high temperature hinders the oxygen surfactant effect and chromium growth proceeds via the formation of mounds and spirals.

► Growth of ultra-thin chromium films on Fe(001) and on Fe(001)-p(1 × 1)O surfaces. ► Growth of the Cr films at different temperatures, namely 380 K and 580 K. ► Oxygen always segregates to the surface. ► At 380 K the surfactant effect of oxygen gives a layer by layer growth. ► At 580 K the growth is three dimensional and the surfactant effect is lost.