Directed Self Assembly and Self-Limiting Growth (SLG) of Mound Formation on Patterned GaAs(001) Surface During MBE Homoepitaxy

We present the results of molecular beam epitaxial growth experiments on nanopit-patterned GaAs(001) surfaces at temperatures near 500$^{\circ}$C. We find that in the initial stage of growth, the pattern directs the spontaneous formation of multilayer islands at 2-fold bridge sites between neighboring nanopits along [110], seemingly due to the presence of an Ehrlich-Schwoebel barrier [1]. However, as growth continues, the height of mounds at 2-fold bridge ``self-limits'': the mounds cease to grow. Beyond this point an initially less favored 4-fold bridge site for mounds dominates and a different pattern of self assembled mounds begins. We propose that a minimum, ``critical terrace size'' at the top of each mound is responsible for the observed self-limiting growth. \\[4pt] [1] T. Tadayyon-Eslami, H.C. Kan, L.C. Calhoun {\&} R.J. Phaneuf, \textit{Phys. Rev. Lett. } \textbf{97}, 126101 (2006)