Competitive role of Mn diffusion with growth in Mn catalyzed nanostructures

The use of dopant as a catalyst in the vapor-liquid-solid mode of growth offers a unique way to dope simultaneously the growing nanostructure. This paper reports the use of Mn as a catalyst to grow ZnS nanostructures and simultaneously doping it. It is also shown here that the diffusion rate of Mn in ZnS can be varied to compete with the growth rate of the nanostructures. The diffusion of Mn is found to depend strongly on the Mn layer thickness. The composition of nanowires is determined from X-ray diffraction (XRD) and X-ray photoemission spectroscopy (XPS) measurements. XPS revealed that Mn diffuses only on the surface forming MnS2 compound and its concentration on the surface of nanowires shows a strong dependence on its droplet size. The thermodynamic models are used to examine the interplay of the growth of ZnS nanostructures and Mn diffusion in them. The results show that uniform doping during the growth can be achieved by carefully tuning the growth temperature and the catalyst layer thickness or c...