Tin versus indium catalyst in the growth of silicon nanowires by plasma enhanced chemical vapor deposition on different substrates

The plasma-assisted Vapor-Liquid-Solid technique has been used to grow Silicon nanowires (SiNWs) on different substrates coated with 1 nm of tin and indium, to study the impact of the surface energy of the substrates on the morphology and structure of the NWs. The characteristics of the prepared Si NWs were analyzed by field emission scanning electron microscopy, X-ray diffraction (XRD) and Raman spectroscopy. The morphological characteristics differ in the density, diameter and length of the synthesized SiNWs. The mean diameters of these SiNWs range from 36 to 51 nm at the bottom and from 15 nm to 34 nm at the tip, while their average length varies from 0.2 μm up to 0.54 μm depending on the substrate and catalyst. The presence of strong peaks in all XRD patterns indicates that the as-grown SiNWs are highly crystalline. The XRD and Raman characteristics of the Sn and In catalyzed SiNWs formed on different substrates show that the crystalline grain size is influenced by the substrate nature and catalyst material, which can be related to the substrate surface energy. In particular shorter NWs with improved crystallinity (larger grain size) are obtained when using Sn as a catalyst on an amorphous silicon-germanium (a-SiGe) substrates, while the small grains were obtained on the same substrate when indium was used as a catalyst.