Ion beam-assisted deposition of nitrides of the 4th group of transition metals

The nitrides of the reactive transition metals of the 4th group (Ti, Zr, Hf) exhibit a number of technologically interesting properties such as high melting points, high hardness, chemical inertness, and decorative appearence. They can be formed by ion beam-assisted deposition at substrates held at room temperature. The nitrides were deposited on silicon by electron beam evaporation of the respective metal under nitrogen ion bombardment with medium to high ion energies (10–30 keV). X-Ray photo electron spectrometry showed that the metals tend to incoporate large amounts of oxygen. This can be reduced by intense ion irradiation. By X-ray diffraction measurements phase formation was determined as a function of the ion-to-atom arrival ratio. The grains show a preferential (100) crystal orientation. The formation of this texture depends on the ion-to-atom arrival ratio and on the metal atomic mass. The films grow in columns which are composed of small crystallites.