Coexistence of two diffusion mechanisms: W on W(100)

We utilized the field ion microscope and density functional theory to investigate surface diffusion and surface adsorption of W on W(100). We demonstrated experimental proof for the occurrence of the exchange diffusion mechanism on W(100) and its coexistence with adatom jump. From our study it is evident that the primary mechanism of motion is atom exchange which is activated on the time scale of seconds at a temperature of around 650 K and is associated with an activation energy of 1.6 eV. Additionally, at a temperature around 700 K we observe a second surface diffusion mechanism with the activation energy estimated as \ensuremath{\sim}2.1 eV, which we associate with adatom jump. Our findings are in excellent agreement with DFT investigations. We have performed the adsorption-desorption experiments as a method helping with determining the morphology of a W(100) surface.