Equilibrium shape of titanium silicide nanocrystals on Si(111)

Abstract

The aim of this work was to find the equilibrium shape of titanium silicide nanocrystals, epitaxially grown on Si(111) in ultrahigh vacuum. To attain the state of equilibrium, the so-grown nanocrystals were subjected to a series of prolonged high-temperature annealing treatments, and closely monitored by scanning tunneling microscopy at every annealing stage. It was established, that the equilibrium shape of the equilibrium phase (C54-$\mathrm{Ti}{\mathrm{Si}}_{2}$) nanocrystals grown by solid-phase epitaxy is a flat, hexagonal island with (01 $\overline{3}$) atomic plain parallel to Si(111), achieved after 750 \ifmmode^\circ\else\textdegree\fi{}C anneal. The nanocrystal behavior is well described by generalized Wulf-Kaishew theorem (adjusted for epitaxial nanocrystals), with their vertical aspect ratio decreasing and the top facet area increasing upon introduction of misfit dislocations at the nanocrystal-substrate interface. Screw dislocations were also observed, and seemed to play a role in facilitating the three-dimensional-to-two-dimensional shape transformation.