Ion Beam Assisted Texture Evolution during Thin Film Deposition of Metal Nitrides
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Ion Beam Assisted Texture Evolution during Thin Film Deposition of Metal Nitrides Bernd Stritzker, Jürgen W. Gerlach, Stephan Six and Bernd Rauschenbach1 Institut für Physik, Universität Augsburg, D-86135 Augsburg, Germany 1 Institut für Oberflächenmodifizierung, D-04318 Leipzig, Germany ABSTRACT 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.
INTRODUCTION Thermal evaporation of the constituents of an alloy is the most common method for the deposition of thin films. The properties of the resulting film can be influenced by only two parameters: - Deposition rate Ja - Temperature of the substrate Very often the resulting thin films do not fulfill the needs from applications with respect to adhesion, texture evolution of the growing film and growth at rather low substrate temperatures. The latter requirement becomes more and more important in the field of protective coatings. Here more and more specific alloys or compounds are used as base materials for the tools to be protected. Thus the coating procedure must not thermally stress the basic tool material. Here it
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was shown in various experiments that it is very advantageous to introduce additional energy via kinetic particles into the growing film. Besides several plasma or sputtering techn
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