  High-index Bi2Se3(221) film has been grown on In2Se3-buffered GaAs(001), in
which a much retarded strain relaxation dynamics is recorded. The slow
strain-relaxation process of in epitaxial Bi2Se3(221) can be attributed to the
layered structure of Bi2Se3 crystal, where the epifilm grown along [221] is
like a pile of weakly-coupled quintuple layer slabs stacked side-by-side on
substrate. Finally, we have revealed the strong chemical bonding at the
interface of Bi2Se3 and In2Se3 by plotting differential charge contour
calculated by first-principle method. This study points to the feasibility of
achieving strained TIs for manipulating the properties of topological systems.
