Characterization of Ti-based nanocrystalline ternary nitride films

Abstract

Ternary nitride coatings of Ti–X–N, where X= Cr, Zr, or B, were deposited at low temperatures (<200 °C) on silicon substrates using ion beam assisted deposition (IBAD). The deposited films were characterized postdeposition using x-ray diffraction (XRD), atomic force microscopy, Rutherford backscattering (RBS), x-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), and nanoindentation. The elemental and phase composition of the films were investigated using XRD, RBS, and XPS measurements. The TiZrN coating was found to consist of a single phase in contrast with TiCrN and TiBN which consisted of three phases, namely, Cr+TiN+Cr2N and TiB2+TiN+BN, respectively. Their optical constants were determined from SE measurements and the phase compositions were deduced from the analysis of these SE data. The elemental compositions deduced from the optically determined phase compositions correlated well with the results obtained from the more direct chemical analysis techniques, namely RBS and XPS. The mechanical properties of the coatings were evaluated using nanohardness testing. The hardness and elastic modulus were measured and were found to be the highest for TiBN (hardness=40 GPa and E = 325 GPa).