CL images have been recorded in rods which show protruding
regions (Fig. 8). The panchromatic CL image [Fig. 8(b)] of a bundle
of rods shows the protrusions as bright regions. In order to
investigate the origin of this behaviour, monochromatic images
have been recorded at the energies of the main CL bands. The protrusions
show bright contrast in the images recorded at 3.2 and
2.3 eV while in the image taken at 1.8 eV appear darker indicating
a lower Mn concentration in these areas. As we mentioned before,
the protruding regions could be the initial stage for the growth of
the hexagonal nanoplates