Novel zinc oxide hexagonal prisms induced by polar surfaces

Three types of novel ZnO hexagonal microprisms have been grown on MgO-coated Si (111) substrates via carbon-thermal evaporation. In this work, the pre-prepared MgO films on the substrates can solve a troublesome lattice mismatch problem in the heteroepitaxy, which has the capability for promoting the formation of the ZnO nuclei. The structural analyses confirm that the structures are perfect single crystals with hexagonal wurtzite structure along the [0001] growth direction. The diameter of the prisms ranges from 0.6 to 2.5 μm and the length is about 3 μm. PL spectra of the ZnO products exhibit a UV emission peak at 388 nm and a broad green emission peak at 514 nm. In addition, the growth mechanism of the crystalline ZnO prisms is discussed briefly, emphasizing the effect of polar orientation on the nucleation.

Research Highlights
► The ZnO morphologies are every novel in our article, and one of them has not been found in other papers.
► The pre-prepared MgO films on the substrates can increase the lattice constants and promote the formation of the ZnO nuclei effectively.
► The polar surface is an important characteristic of ZnO. The growth mechanism of ZnO prisms is discussed, emphasizing the effect of polar surface.
► Carbon-thermal evaporation is a simple and cost-effective approach for growing prisms on a relatively large scale.