For reference, polarized Raman SP600125 mouse scattering was performed on a bulk InAs (110) substrate. The polar scan of the Raman intensity of the TO phonon is shown in Figure 2b. The experimental data show good agreement with the theory. The small shift of the TO intensity maxima of about 2° is attributed to an inclination of the polarization see more direction of the light with respect to the crystallographic axes of the substrate. It should be pointed out here that LO scattering is forbidden in this scattering configuration. Figure 2 Calculated intensity polar patterns of scattered light and measured polarized Raman scattering of TO phonon. (a) Calculated intensity polar patterns of the scattered

light polarized perpendicular (I ⊥) or parallel (I ∥) to the [111] direction as a function of the angle ϕ of the incident polarization with respect to [111] selleck screening library is shown for TO phonons in backscattering from a bulk InAs (110) substrate. (b) Measured polarized Raman scattering of the

TO mode on a reference bulk InAs (110) substrate. Spheres and open squares represent the parallel and perpendicular components of the Raman signal, respectively. The continuous line is a squared sine fit to the data. In order to calculate the polar patterns of I s for NWs, one has to take into account the additional degree of freedom associated with the rotation of θ around the NW axis since it can influence the polar patterns of the optical modes. Based on [23], this angular dependence is a clear signature of the presence of zinc-blende TO modes and can be used for their assignation. Results and discussion The epitaxial relationship between

the InAs NWs and Si (111) substrate and the predominant crystal structure of these NWs were analyzed by XRD and TEM (Figure 3). The out-of-plane symmetric XRD 2θ − ω scan shown in Figure 3a, which was obtained from the as-grown NWs, indicates that NWs were grown epitaxially on the Si substrate. Besides the <111> reflection of Si at 28.4°, another reflection at 25.4° represented (111) of InAs. The weak peak of Si (111) may be due to not compensating for the 3.28° miscut of the Si substrate. Representative high-resolution TEM (HRTEM) images of these nanowires are Cyclin-dependent kinase 3 presented in Figure 3b,c. Stripes with different contrast are observed along the nanowires. Careful analysis indicates that these correspond to the twin defects perpendicular to the growth axis. The detail of such defect is presented in Figure 3b. Figure 3c shows the HRTEM image of a NW with its inset showing the fast Fourier transform (FFT) image. The HRTEM image combined with the FFT image indicates that the InAs NW has a cubic, zinc-blende structure and grows along the <111> direction normal to the Si (111) substrate. The growth axis remains parallel to the (111) B direction. Figure 3 XRD scan, low-resolution TEM, and HRTEM of a selected InAs nanowire array sample.