Ab-initio investigation of the early stage of nano-scale thin film growth: Co and Al adatoms on Co (111) surface

We considered the diffusion behavior which occurred in the initial stages of thin film deposition for fabrication of tunneling magneto-resistance (TMR) junction with the use of ab-initio density functional theory. Al adatom deposited on the Co (111) substrate had the most stable configuration when it is adsorbed on hcp site and the energy barrier for the diffusion to neighbor fcc or hcp site was low enough to move freely. The energy barrier for the Co on the Co substrate was about 3.8 times higher than Al on Co case. The energies for the step down (step energy barrier) of adatom from the top of the adatom trimer were estimated as 0.15 eVand 1.27 eV for Al/Al trimer/Co and Co/Co trimer/Co, respectively.