Search

In this article, we compare the excitation wavelength dependence of the polarization anisotropy (ρ) of an internal field induced Raman scattering signal in individual bare InAs and InAs/GaSb core-shell nanowires. The measured value of ρ of the Raman scattering intensity for InAs/GaSb core-shell nanowires has a minimum at ∼500 nm, while for the bare InAs nanowire, the value of ρ monotonically increases over the same range of wavelengths. We have modeled the scattering intensities of both systems by considering the joint role of Raman tensor components and confinement of electromagnetic radiation inside the nanowire at two orthogonal polarization configurations of the electromagnetic radiation. The theoretical results allow us to understand that the observed behavior of ρ is related to the nanowire geometry and to the difference in the wavelength dependence of the dielectric constants of InAs and GaSb. This work shows the possibility of manipulating the polarization anisotropy by selecting suitable diameters and materials for the core and the shell of the nanowire. We also report a six-fold increase in Raman scattering intensity due to the GaSb shell on InAs nanowires. [ABSTRACT FROM AUTHOR]

We study band alignment in wurtzite/zinc-blende polytype InAs heterostructured nanowires using temperaturedependent resonance Raman measurements. Nanowires having two different wurtzite fractions are investigated. Using visible excitation wavelengths in resonance Raman measurements, we probe the electronic band alignment of these semiconductor nanowires near a high-symmetry point of the Brillouin zone (E1 gap). The strain in the crystal structure, as revealed from the shift of the phonon mode, explains the observed band alignment at the wurtzite/zinc-blende interface. Our experimental results are further supported by electronic-structure calculations for such periodic heterostructured interface. [ABSTRACT FROM AUTHOR]

Abstract: An internal field induced resonant intensity enhancement of Raman scattering of phonon excitations in InAs nanowires is reported. The experimental observation is in good agreement with the simulated results for the scattering of light under varying incident wavelengths, originating from the enhanced internal electric field in an infinite dielectric cylinder. Our analysis demonstrates the combined effect of the first higher lying direct band gap energy (E 1) and the refractive index of the InAs nanowires in the internal field induced Raman scattering. Furthermore, the difference in the relative contribution of electro-optic effect and deformation potential in Raman scattering of nanowires and bulk InAs over a range of excitation energies is discussed by comparing the intensity ratio of their LO and TO phonon modes. [Copyright &y& Elsevier]

We report electron transmission and Raman spectroscopy study of InAs nanowires. We demonstrate that the temperature dependent behavior of optical phonon energies can be used to determine the relative wurtzite fraction in the InAs nanowires. Furthermore, we propose that the interfacial strain between zincblende and wurtzite phases along the length of the wires manifests in the temperature-evolution of the phonon linewidths. From these studies, temperature-dependent Raman measurements emerge as a non-invasive method to study polytypism in such nanowires. [ABSTRACT FROM AUTHOR]

Resonance Raman measurements are carried out on defect-free wurtzite GaP nanowires over the excitation energy range between 2.19 and 2.71 eV. Resonances of the E1(LO) and A1(LO) modes demonstrate the existence of energy states with Γ9hh and Γ7V (Γ7C) symmetries of the valence (conduction) band and enable us to measure wurtzite phase GaP band energies. In addition, we have performed temperature dependent resonant Raman measurements, which allowed us to extrapolate the zero temperature values of Γ point energies. Our results provide the necessary feedback required for refining the available theoretical calculations to derive the correct wurtzite III-V semiconductor band structure. [ABSTRACT FROM AUTHOR]

The article presents a mapping of the residual strain along the axis of InAs/InSb heterostructured nanowires. Using confocal Raman measurements, we observe a gradual shift in the transverse optical phonon mode along the axis of these nanowires. We attribute the observed shift to a residual strain arising from the InAs/InSb lattice mismatch. We find that the strain is maximum at the interface and then monotonically relaxes towards the tip of the nanowires. We also analyze the crystal structure of the InSb segment through selected area electron diffraction measurements and electron diffraction tomography on individual nanowires. [ABSTRACT FROM AUTHOR]