A Raman-scattering study on the interface structure of nanolayered TiAlN/TiN and TiN/NbN multilayer thin films grown by reactive dc magnetron sputtering

摘要

Nanolayered multilayer coatings of TiAlN/TiN and TiN/NbN were deposited on Si (100) substrates at various modulation wavelengths (i.e., bilayer thickness, Λ) using a reactive dc magnetron sputtering system. These coatings were characterized using micro-Raman spectroscopy to study the effect of interfaces on the optical-phonon modes. For TiAIN/TiN multilayers, the optical-phonon band shifts to higher frequencies with a decrease in the modulation wavelength. Furthermore, the optical-phonon band shifts to higher frequencies with an increase in the substrate temperature for TiAlN/TiN multilayers deposited at Λ = 80 A. No such shift was observed for single-layer TiN and TiN/NbN multilayer coatings. This observed shift has been attributed to interdiffusion between the layers during deposition, which is more for TiAlN/TiN multilayers as compared to TiN/NbN multilayers. The x-ray-diffraction data showed well-defined satellite reflections for TiN/NbN multilayers at low modulation wavelengths and very weak satellite reflections for TiAlN/TiN multilayers, indicating that interfaces were very broad for TiAlN/TiN multilayers. The nanoindentation data showed no significant improvement in the hardness of TiAlN/TiN multilayers as compared to the rule-of-mixture value, whereas TiN/NbN multilayers showed an improvement in the hardness, which was two times the rule-of-mixture value. The low hardness of TiAlN/TiN multilayers has been attributed to interfacial diffusion.