Non-Epitaxial Surface-Guided Core-Shell Nanowires

One-dimensional nanostructures such as nanowires (NWs) have attracted a lot of attention due to their great potential in nano-technological applications and scientific research. Our group developed a method to grow aligned NWs such that the crystallographic orientation and growth direction are dictated by epitaxial and grapho-epitaxial relations with the substrate. By now, our group succeeded to grow guided ZnO, ZnSe, ZnTe, CdSe and CdS NWs on sapphire and GaN on SiC, spinel and sapphire. The guided growth approach allows easy integration of semiconductor NWs into a variety of nano-devices such as field-effect transistors, photodetectors and photovoltaic cells. Some of these applications, such as light emitting diodes (LEDs) or photovoltaic cells, demand synthesis of nano-heterostructures. Our group has successfully produced core-shell ZnSe-ZnTe and CdS-CdSe NWs with epitaxial relationship between the core and the shell. In this work, we rely on the synthetic processes of different semiconductor NWs previously developed in our group to concentrate on the growth of non-epitaxial surface-guided core-shell NWs. The heterostructure is assembled by a core made of n-type GaN with wurtzite crystallographic structure and a shell made of p-type ZnTe with zinc-blend crystallographic structure. We study the crystallographic properties and elemental composition of the core-shell NWs by examining thin cross-sectional lamellae using transmission electron microscopy (TEM). In addition, we preformed photoluminescence and cathodoluminescence measurements in order to analyze the optical and compositional properties of the structure.