In-situ x-ray diffraction studies concerning the influence of Al concentration on the texture development during sputter deposition of Ti-Al-N thin films

In-situ x-ray diffraction was employed during the growth of thin Ti_1-xAl_xN films, using a deposition chamber installed at a synchrotron radiation beamline. The films were deposited by reactive co-sputtering from Ti and Al targets. At constant x ~ 0.06, substrate temperature, bias voltage, and nitrogen partial pressure, and thus growth rate, was varied. Further, x was systematically varied from 0 to 0.73 while keeping all the other parameters constant. x < 0.15 and high deposition rates of ~ 1 Å/s lead to the typical crossover behavior between initial (001) and final (111) off-plane preferred orientation. Reducing the deposition rate to < 0.5 Å/s leads to a reversed behavior with a clear (001) preferred orientation above a film thickness of 600 Å which is essentially independent of the substrate temperature. Keeping the deposition rate low, the (111) preferred orientation can be recovered for x > 0.15, which can be explained by the higher adatom mobility of Al compared to Ti in the presence of atomic nitrogen. Increasing x towards the AlN segregation threshold at x ~ 0.60 leads to hard nano-composite nc-TiAlN/AlN structures, and x > 0.73 finally leads to dominant AlN with an a-axis off-plane texture.