Growth and intermixing of Nb on Fe(110) and Fe on Nb(110)

The growth system Nb/Fe and the reversed system Fe/Nb were studied on the (110) surface using Scanning Tunneling Microscopy (STM). For Nb/Fe(110) we present in situ STM results as a direct evidence of a Nb/Fe exchange mechanism at temperatures above 400 K that leads to the formation of a surface alloy.

Since the experiments on Nb(110) were done on Nb buffer layers the fabrication of those is discussed. We show that besides Al₂O₃ (112¯0) wafers a W(110) single crystal can serve as a support for Nb(110) buffer layers which is more convenient for STM measurements. The niobium oxide adlayer that is present on nearly all Nb surfaces can be avoided by thorough degassing of the Nb source.

Results on Fe/Nb(110) are discussed in the temperature range from room temperature (RT) to 1000 K. At RT no intermixing of Fe and Nb was observed and with very low deposition rates epitaxial films can be grown. An ordered dislocation network was observed in the first Fe layers. Above 800 K two adatom island species are present as the manifestation of an alloying process. The formation of an Fe–Nb surface alloy which in the submonolayer regime is interspersed with chains of pure Fe is suggested.