Growth and characterization of gold catalyzed SiGe nanowires and alternative metal-catalyzed Si nanowires

Nanoscale elemental quantification in heterostructured SiGe nanowires

The nanoscale chemical characterization of axial heterostructured Si1-xGex nanowires (NWs) has been performed using scanning Auger microscopy (SAM) through local spectroscopy, line-scan and depth profile measurements. Local Auger profiles are realized with sufficient lateral resolution to resolve individual nanowires. Axial and radial composition heterogeneities are highlighted. Our results confirm the phenomenon of Ge radial growth forming a Ge shell around the nanowire. Moreover, quantification is performed after verifying the absence of preferential sputtering of Si or Ge on a bulk SiGe sample. Hence, reliable results are obtained for heterostructured NW diameters higher than 100 nm. However, for smaller sizes, we have noticed that the sensitivity factors evaluated from bulk samples cannot be used because of edge effects occurring for highly topographical features and a modified contribution of backscattered electrons.

Reflection-mode, confocal, tip-enhanced Raman spectroscopy system for scanning chemical microscopy of surfaces

A reflection-mode, confocal, tip-enhanced Raman spectroscopy system for nanoscale chemical imaging of surfaces is presented. The instrument is based on a beam-bounce atomic force microscope with a side-on Raman microscope with true confocal light illumination and collection. Localized vibrational (Raman) spectroscopy is demonstrated at length scales down to 20 nm on opaque samples. The design and validation of the instrument are discussed with quantitative emphasis on confocal microscope operation, plasmonic properties of the tip, point spectroscopy, and Raman imaging of SiGe nanowires.