Mn Adsorption on the GaAs(111)-(2x2)B Surface: First Principles Studies

Mn adsorption on the GaAs(111)-(1 x 1)B surface electronic and magnetic properties are investigated using first principles total energy calculations within the periodic spin polarized density functional theory. Results show that one Mn atom adsorption on top of the surface drives to an interstitial Mn atom. The interstitial atom is bonded to three first monolayer As atoms forming a chain like structure. This stable structure has a ferromagnetic behavior with a Mn magnetic moment of similar to 3.98 mu(B). The Mn coverage increase yields a stable structure with the creation of an interstitial Mn layer, which in turn gives rise to a GaNln As like alloy at the surface. The layer displays a ferromagnetic characteristic with magnetic moment of similar to 4.40 mu(B). A surface formation energy analysis of all these stable structures shows that one Mn interstitial monolayer and a Mn interstitial atom may coexist. Density of states shows that there is an important contribution of the Mn atoms to the occupied and unoccupied states. The DOS of one Mn monolayer is metallic with the most important contribution around the Fermi level coming from the Ga-p and Mn-d orbitals.