  Complex electron-microscopic, energy-dispersed and wide-temperature optical
absorption and photoluminescence (PL) investigations are carried out into
Bridgeman-grown layered In2Se3 crystals. It is shown that In2Se3 crystals as a
whole have a homogeneous concentration of In and Se atoms, corresponding with
In2Se3 stoichiometry. Nevertheless, In2Se3 crystals contain a significant
amount of dislocations, on which nano-sized interspersions of crystal phases of
pure InSe, In6Se7 and monoclinic red Se settle down. Optical wide-temperature
investigations of In2Se3 allow us to do the following: establish the width of
the band-gap, the exciton binding energy; determine the frequency of a
half-layer A-phonon, which takes part in electron (exciton)-phonon interaction;
and to evaluate the effective masses of carriers and the dielectric
permeability. Finally, blue shift of the band-gap and character of the electron
(exciton)-phonon interaction of nano-sized 3D InSe crystals confined in an
In2Se3 crystal matrix; influence of an InSe nanocrystal radius and of an
ensemble of 3D InSe nanocrystals with different radii for an increase of the
exciton emission/absorption half-width line with temperature and radii of InSe
nanocrystals are discussed.
