Vibrational modes in GaxMn1−xSb studied by Raman spectroscopy

Raman scattering study on vibrational modes has been reported in ferromagnetic semiconductor Ga_1-xMn_xSb grown by Mn ions implantation, deposition, and post-annealing. The Raman experiments are performed in the implanted and unimplanted regions of the sample before and after etching. Only GaSb-like phonon modes are observed in the spectra measured from the unimplanted region. However, in addition to GaSb-like phonons, some extra modes are observed in the spectra measured from the implanted region of the sample. The experimental results demonstrate that the 115, 152, and 437 cm^-1 modes are appeared due to surface defects and crystal disorder caused by Mn ions implantation and deposition processes. The origin of the weak structure observed approximately at 269 cm{-1} is not so clear. However, the frequency position of MnSb-like LO phonon mode (266.4 cm^-1) determined by reduced-mass model is found to be close to the experimentally observed mode at 269 cm^-1. The phonon mode appeared approximately at 659 cm^-1 is found to be associated with blackish layer formed on the surface of the sample from the annealing process and is assigned to Mn₃O₄-like. Furthermore, existence of coupled LO-phonon plasmon mode is found in the spectra measured from the implanted and close to the implanted regions of the sample.