Blueshifted Raman scattering and its correlation with the  growth direction in gallium oxide nanowires
The Raman spectrum of gallium oxide (β-Ga2O3) nanowires with  growth direction is identical to that of the bulk Ga2O3 [Y. C. Choi et al. Adv. Mater. 12, 746 (2000)] while that of β-Ga2O3 nanowires with  growth direction is redshifted by 4-23 cm-1 [Y. H. Gao et al. Appl. Phys. Lett. 81, 2267 (2002)]. Here we report the Raman and Fourier transform infrared spectra of β-Ga2O3 nanowires with  growth direction which is blueshifted relative to the bulk spectra by ~10-40 cm-1. Based on a first principles calculation of the strain dependence of Raman mode frequencies in bulk β-Ga2O3, we correlate the observed frequency shifts to growth-direction-induced internal strains in the nanowires.