Tip-enhanced Raman mapping of a single Ge nanowire

We report the nanometer scale mapping of a single Ge nanowire (NW) using tip-enhanced Raman scattering (TERS). The Raman spectra of a single Ge NW show downshift and asymmetric broadening, depending on the diameter, due to the phonon confinement effect. A Raman peak attributed to amorphous Ge has also been observed. Assuming the crystalline core/amorphous shell structure, we estimate the amorphous shell thickness to be 2-6 monolayers from the integrated Raman intensities of crystalline and amorphous Ge. (C) 2011 American Institute of Physics. [doi:10.1063/1.3621856]