This Thesis explores amorphous transition metal nitrides for cutting tool applications. The aim is to extend the knowledge on amorphous nitride thin lms, to describe the growth process, and to explore ways of characterizing these novel complex materials.

Thin lms of Ti-Al-Si-N and Hf-Al-Si-N were fabricated using industrial cathodic arc evaporation and magnetically-unbalanced reactive magnetron sputtering, respectively. The microstructure of the lms was studied using x-ray diraction (XRD) and transmission electron microscopy (TEM), while compositional analysis of the lms was performed by spectroscopic techniques (EDS, SIMS, and RBS). The mechanical properties were investigated by nanoindentation.

The Ti-Al-Si-N lms were grown on cemented carbide substrates using Ti-Al-Si compound cathodes in an N2 atmosphere. High Al and Si concentrations in the lms (i.e., 12 at% Si and 18 at% Al) promote renucleation and result in x-ray amorphous lms. High resolution TEM (HRTEM) reveals isolated grains, ~2 nm in size, embedded in an amorphous matrix. Annealing experiments show that the lms are thermally stable up to 900 ^oC. They exhibit age hardening, with an increase in hardness from 21.9 GPa for as-deposited lms to 31.6 GPa at 1000 oC. At 1100 ^oC severe out-diusion of Co and W from the substrate occurs, and the lms recrystallize into c-TiN and w-AlN.

The single layer Hf-Al-Si-N and multilayer Hf-Al-Si-N/HfN lms were grown on Si(001) substrates from a single Hf_0:60Al_0:20Si_0:20 alloy target in an N₂/Ar atmosphere. The composition and nanostructure of the lms was controlled during growth by independently varying the ion energy (E_i) and the ion-to-metal flux ratio (J_i=J_Me). With J_i/J_Me=8, the nanostructure and composition of the lms changes from x-ray amorphous with a Hf content of 0.6, to an amorphous matrix with encapsulated nanocrystals with 0.66≤Hf≤0.84, to nanocrystalline with 0.96≤Hf≤1.00, when increasing E_i from 15 to 65 eV. Varying J_i=J_Me with E_i=13 eV yields electron-diraction amorphous lms at substrate temperatures of 100 ^oC. Hf-Al-Si-N/HfN multilayers with periods Λ=2-20 nm exhibit enhanced fracture toughness compared to polycrystalline VN, TiN, and Ti_0:5Al_0:5N reference samples; multilayer hardness values increase from 20 GPa with Λ=20 nm to 27 GPa with Λ=2 nm.

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