  The growth and annealing behavior of strongly twinned homoepitaxial films on
Ir(111) has been investigated by scanning tunneling microscopy, low energy
electron diffraction and surface X-ray diffraction. In situ surface X-ray
diffraction during and after film growth turned out to be an efficient tool for
the determination of twin fractions in multilayer films and to uncover the
nature of side twin boundaries. The annealing of the twin structures is shown
to take place in a two step process, reducing first the length of the
boundaries between differently stacked areas and only then the twins
themselves. A model for the structure of the side twin boundaries is proposed
which is consistent with both the scanning tunneling microscopy and surface
X-ray diffraction data.
