Ion beam assisted deposition, i.e., the bombardment of thin films with a
beam of energetic particles has become a highly developed tool for the
preparation of thin films. This technique provides thin films and coatings
with modified microstructure and properties. In this paper examples are
presented for the modifying of the structure: in-situ modification of
texture during ion beam assisted film growth and ion beam enhanced
epitaxy.
The biaxial alignment of titanium nitride films prepared on Si(111) by
nitrogen ion beam assisted deposition at room temperature was studied. The
bombardment perpendicular to the surface of the substrate causes an {001}
alignment of crystallites. A 55° ion beam incidence angle produces both a
{111} orientation relative to the surface and a {100} orientation relative
to the ion beam. This results in a totally fixed orientation of the
crystallites. The texture evolution is explained by the existence of open
channeling directions.
Epitaxial, hexagonal gallium nitride films were grown on c-plane sapphire by
low-energy nitrogen ion beam assisted deposition (≤ 25 eV). The ion energy
was chosen to be less than the corrected bulk displacement energy to avoid
the formation of ion-induced point defects in the bulk. The results show
that GaN films with a nearly perfect {0002} texture are formed which have
superior crystalline quality than films grown without ion irradiation. The
mosaicity and the defect density are reduced.
By applying an assisting ion beam during pulsed laser deposition of aluminum
nitride on the c-plane of sapphire, epitaxial, hexagonal films could be
produced. The results prove the beneficial influence of the ion beam on the
crystalline quality of the films. An optimum ion energy of 500 eV was found
where the medium tilt as well as the medium twist of the crystallites was
minimal.