Wurtzite-twinning-induced growth of three-dimensional II-VI ternary alloyed nanoarchitectures and their tunable band gap energy properties.

Abstract

By controlling the growth kinetics, we succeeded in growing wurtzite-twinning-induced three-dimensional (3D) alloyed ternary ZnSexS1-x nanoarchitectures with controlled morphologies and chemical composition via a vapor-solid (VS) process. The lattice constants of the alloyed ZnSexS1-x are linearly dependent on the chemical constituent stoichiometry. Compared with the (102) and (101) twinning in wurtzite structure, the wurtzite {013} twinning with the lowest energy is proved to be an effective route to self-assemble ZnSexS1-x building blocks into bicrystalline and tricrystalline 3D branched nanoarchitectures of different configurations and morphologies. The twinned structure formation is related to growth kinetics at a relatively high temperature. It is the {013} twinning that can accelerate the growth of the 3D nanoarchitectures adapting their specific branching structures, while such characteristic branches are not induced by surface polarity of the II-VI materials. The difference in the final structures and configurations depends on the starting nucleus of the stretching branches, and the type of the nucleated twinning is the key factor in dictating the final nanostructures. Bicrystalline ZnSe0.4S0.6 3D nanoarchitectures are induced by the (013) twin, with the stretched branches growing along [10] direction with an angle of 148 degrees. For the tricrystalline 3D nanoarchitectures, the zinc blende phase is not present at the core of the ZnSe0.4S0.6 3D nanoarchitectures. The stretched branches grow along the [001] direction and share a common twin plane of (013) with an angle of 109.5 degrees between the branches. Cathodoluminescence examination at 10 K reveals that band gap energy can be tuned via chemical composition modification of the alloyed ZnSexS1-x structures. However, a linear relationship does not exist between the near band energy and the chemical composition of the alloyed ZnSexS1-x. This result should be of great significance to realize band gap engineering via chemical composition modification of high-quality alloyed II-VI ternary compound semiconductors.