Intermixing and surface alloying in Hf and Zr ad-layers on W(100)

Hafnium or zirconium layers of thickness from a fraction of geometrical monolayer up to 2 monolayers were vapor-deposited under ultra high vacuum on the surface of the (100)-oriented W single crystal and gradually annealed at various temperatures from 300 to 2100 K. Intermixing, interdiffusion, and alloying of Hf or Zr adlayers on W(100) were observed and studied by scanning tunneling microscopy (STM), low energy electron diffraction (LEED), and Auger electron spectroscopy (AES). Two surface alloys of different stoichometry have been identified for both Hf/W(100) and Zr/W(100) adsorption systems. Influence of oxygen adsorption on topography and morphology of Zr adlayers deposited on stepped W(100) surface was studied by STM. Formation of islands of Zr₃W surface alloy surrounded by bunched steps was observed in this case.