The size and microstructure of the product were
further examined with transmission electron microscopy
(TEM) and high-resolution TEM, respectively.
From the TEM image displayed in Fig. 3b, we can find that the
CuInSe2 nanoparticles still aggregated to some extent,
although 20 min of sonication was employed in order to
disperse it before the sample was deposited on the carboncoated
copper grid for the TEM measurement.
The size is about 80–90 nm, almost consistent with that observed from
SEM image.
The HRTEM image of the nanoparticles is
shown in Fig. 3c, where the lattice fringe is measured to be
0.34 nm corresponding to the (112) lattice plane of
tetragonal CuInSe2.
The three ring selected area electrical
diffraction (SAED) pattern shown in Fig.
3d corresponds to the (112), (220)/(204), (116)/(312) reflection direction of
the tetragonal CuInSe2.
The SAED rings are not continuous but are composed of many discrete spots, not only suggesting
the complex polycrystalline but also implying a preferential orientation of the collective CuInSe2 nanoparticles.