Paper TF-WeA4
The Influence of Oxygen Impurities on the Formation of Self-Assembled Nanostructures in Al/Al(110) Homoepitaxy

Wednesday, October 22, 2008, 2:40 pm, Room 302

Recent experimental studies of Al/Al(110) homoepitaxy show that self-assembled nano-structures can form due to an interplay between the kinetics of diffusion and deposition.¹ These “nanohuts” are characterized by smooth {111} and {100} facets. At temperatures between 330 and 500 K and for a deposition rate of 1 ML/min, the nanohuts emerge after about 10 ML have been deposited. Upon further deposition, these huts grow and self-organize, reaching average heights of 50 nm after 30 ML has been deposited. Understanding the formation of these features and developing the capability to control them in this and similar systems is both scientifically and technologically significant. To predict the formation and self-organization of these features, we employ first-principles calculations based on density-functional theory to study diffusion and atomic interactions on Al surfaces. We quantify many-body interactions between Al adatoms,² as well as the interactions between Al adatoms and isolated O impurities on Al(110). The interactions between Al and O atoms are expected to be especially important in the initial stages of growth, as oxygen is a common impurity on Al surfaces, even in ultra-high vacuum environments. We show that O impurities can significantly influence island nucleation and lead to entirely different growth modes than those observed in pure Al/Al(110) homoepitaxy. Using kinetic Monte Carlo, we simulate multi-layer growth under various conditions to predict the growth morphologies and understand the implications of surface impurities for self-assembled nanostructures.

¹ F. Buatier de Mongeot, W. Zhu, A. Molle, R. Buzio, C. Boragno, U. Valbusa, E. Wang, and Z. Zhang, Phys. Rev. Lett. 91, 016102 (2003).
² Y. Tiwary and K. A. Fichthorn, Phys. Rev. B 75, 235451 (2007).