Vibrational properties of semiconductor nanowires and nanowire heterostructures: ensembles and single nanowires

Raman spectroscopy is becoming a standard method for the non-destructive characterization of nanowires and their heterostructures due to its ability to deliver information about size, structure, carrier concentration, local density, strain and orientation. Several phenomena related to vibrations and the anisotropic nature of nanowires have been reported. The so called Raman antenna effect leads to an increase of the scattering intensity that depends on nanowire size, orientation and excitation wavelength. Surface related vibrational modes have been proved to be sensitive to nanowire dimensions and their dielectric environment. Interface and confined modes characteristic of nanowire heterostructures have also been reported, together with low frequency modes that involve the vibration of the nanowire as a whole. Resonant inelastic light scattering has demonstrated its capability of providing information about the internal structure of individual nanowires and nanowire ensembles, increasing at the same time the Raman scattering efficiency. Furthermore, the coupling of the phonons with real electronic excitations gives access to band structure characteristics that cannot be accessed by other means. In this review we analyse the most recent advances concerning the vibrational properties of nanowire ensembles and single nanowires, paying special attention to their potential applications. ((c) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)