Plasmons dispersion and nonvertical interband transitions in
single-crystal Bi2Se3 investigated by electron energy loss spectroscopy
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by
S. C. Liou, M.-W. Chu, R. Sankar, F.-T. Huang, G.-J. Shu, F. C. Chou,, C. H. Chen
2013
Abstract
Plasmons dispersion and nonvertical interband transitions in Bi2Se3 single
crystals were investigated by electron energy-loss spectroscopy in conjunction
with (scanning) transmission electron microscopy, (S)TEM-EELS. Both volume
plasmons (π plasmon at 7 eV and π+σ plasmon at 17 eV) and
surface plasmons ( 5.5 and 10 eV) were demonstrated in STEM-EELS spectra and
the corresponding spectral imaging in real space. In the further EELS
experiments in reciprocal space, the momentum-dependent spectra reveal very
different dispersion behavior between π and π+σ plasmons, with
π+σ plasmons showing a typical quadratic dependence whereas the
π plasmon exhibiting a linear dispersion analogous to what was reported for
graphene. Furthermore, a low energy excitation 0.7 1.6 eV was also observed
which is attributed to direct nonvertical interband transitions along the
gamma-F direction.
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