Ion Beam Assisted Texture Evolution during Thin Film Deposition of Metal Nitrides

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.