| The investigation had as a general goal the deposition of thin films that possess high erosion wear resistance. The fabrication technique used for this purpose was an industry-compatible process called reactive sputtering physical vapor deposition (PVD). The study specifically involved depositing Ti-Si-N nc-composite thin films according to generic design principles that specify using a transition metal nitride and a covalent nitride material system in order to produce hard coatings (∼50 GPa Vickers hardness).; Thin films were deposited using reactive pulsed, do sputtering to avoid arcing issues and for wider control over the process properties such as the deposition rate and level of bombardment. Two sputter guns used synchronized pulsed do signals, which were asymmetric and bipolar with positive voltages of less than +100 V and negative voltages of -500 to -1000 V. The pulsing frequency was varied in this co-deposition system as a possible means to control the nanocrystalline composite thin film properties by controlling the level of bombardment.; The thin films were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM) to determine the crystallinity of the films. XRD results show the presence of the (111), (220), and (200) orientations with the later being most common. TEM bright-field images show nanocrystals in the 10 to 40 nm range, depending on the pulsing frequency. A columnar morphology (50--120 nm diameters) was observed in the nc-composite films from images taken with a scanning electron microscope.; Verification of the TiN and SiN phases was accomplished using XPS to analyze the binding energies of Ti 2p and Si 2p electrons, respectively. Oxygen was detected in the films, (2--9 at.%) depending on pulsing frequency, and it severely worsened the mechanical properties, specifically the hardness, by reacting with some of the silicon in the SiN phase. A maximum Vickers hardness, Hv, of 32 GPa and reduced elastic modulus, Er, of 290 GPa were measured using displacement controlled nanoindentation. Normalized nanoindentation depths of 5, 10 and 15% of the film thickness were performed and showed that normalized indent depths of 10% produced reliable data.; Analysis of the plasma properties in situ shows variation in the ionized species, their density, and energy as a function of pulsing frequency. A Langmuir probe and energy-resolved mass spectrometer (Hiden probe) were used to analyze the conditions at the substrate position within the deposition chamber. The major ion constituent in the plasma was N2 + with N+, Ti+, SiN+, and TiN+ comprising the remaining species. The energy analysis of N2+ and N+ show that the energy distribution is bimodal with the majority of ions < 5 eV, while a secondary, less intense peak of 70 to 75 eV exists.; This information was used to calculate a universally applicable momentum-per-atom figure of merit at the growing film surface during deposition. The nc-composites deposited at 10 mT N2 show that as the momentum-per-atom increases, so do the Hv and Er. The nc-composites deposited at 5 mT N2 show a negative correlation to the content of (111) orientation in the films, which itself correlates to the momentum-per-atom. |
