Optical properties of nanostructured Al-rich Al1 − xTixN films

Al1 − xTixN thin films received significant scientific and technological interest due to its exceptional mechanical performance. However, its optoelectronic properties did not receive so much attention, despite of being particularly interesting because of the performance of their constituents (TiN and AlN), which are a conductor and a wide bandgap semiconductor, respectively. In this work we have grown Al-rich Al1 − xTixN films covering the x range 0 < x < 0.365 and forming the wurtzite and rocksalt crystal phases. We report the variation of the direct and indirect optical gaps (associated with the w-AlN and cubic AlN, respectively) and of the Urbach energy EU (associated with the structural disorder) vs. the composition x and we correlate the values of the optical gaps with the structural and chemical features of Al1 − xTixN, which were evaluated by X-ray diffraction and X-ray photoelectron spectroscopy.