Observation and Control of Interfacial Defects in ZnO/ZnSe Coaxial Nanowires

Observation and Control of Interfacial Defects in ZnO/ZnSe Coaxial Nanowires W.A. Bhutto, Z.M. Wu∗, Y.Y. Cao, W.P. Wang and J.Y. Kang∗ Fujian Key Laboratory of Semiconductor Materials and Applications, Department of Physics, Xiamen University Xiamen 361005, P.R. China ZnO/ZnSe coaxial nanowires with di erent ZnO core diameters were synthesized by using a two-step chemical vapor deposition. The scanning electron microscopy images demonstrated that the coaxial nanowires with small ZnO core diameter had the smoother surface than that with large ZnO core diameter. A coherent ZnSe layer with wurtzite structure was observed in the nanowire interface between the ZnO core and the ZnSe shell by high resolution transmission electron microscopy. This coherent layer is bene cial to reduce the defect density and improve the crystal quality by suppressing the phase transition. It was found that the coherent thickness was signi cantly related to the ZnO core diameter. For the nanowire with large ZnO core, a thin critical thickness of 2 3 nm was obtained. As a result, a layer of zinc blende ZnSe appeared outside the nanowire, and a lot of defects existed in the interface between the ZnSe layers with di erent phase structures. For the nanowire with small ZnO core, however, the critical thickness increased and a coherent coaxial structure was observed with the same lattice spacing in the ZnO core and the ZnSe shell. To obtain defect-free coaxial nanowire, an optimal structure was also proposed by theoretical calculation.