Specific features of Raman spectra of III–V nanowhiskers |
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Authors: | S V Karpov B V Novikov M B Smirnov V Yu Davydov A N Smirnov I V Shtrom G E Cirlin A D Bouravleuv Yu B Samsonenko |
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Institution: | 1.Fock Institute of Physics,St. Petersburg State University,Petrodvorets, St. Petersburg,Russia;2.Ioffe Physical Technical Institute,Russian Academy of Sciences,St. Petersburg,Russia;3.St Petersburg Academic University-Nanotechnology Research and Education Centre,Russian Academy of Sciences,St Petersburg,Russia;4.Institute for Analytical Instrumentation,Russian Academy of Sciences,St. Petersburg,Russia |
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Abstract: | Raman spectra of GaAs nanowhiskers that are grown on different substrates and differ from one another by the content of the
sphalerite and wurtzite phases have been investigated. Special attention has been focused on the manifestation of structural
features in the scattering spectra of nanowhiskers. It has been established that the nanowhiskers are characterized both by
random inclusions of wurtzite layers in the sphalerite structure and by the continuous growth in the wurtzite phase. The interpretation
of the scattering spectrum agrees with the concept of summation of the dispersion curves of the sphalerite structure upon
transition to the wurtzite structure, which leads to a transformation of zone-boundary modes at the L point of the Brillouin zone into zone-center modes of the wurtzite structure and, as a consequence, to the appearance of
a number of new fundamental modes of different symmetries. An analysis of the Raman spectra has revealed the formation of
the hexagonal 4H polytype in narrow layers of nanowhiskers due to a random packing of hexagonal layers. The coexistence of the sphalerite
and wurtzite phases in GaAs nanowhiskers completely correlates with the photoluminescence spectra measured for the same samples. |
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