| HfNx the most refractory transition-metal nitride, is of technological importance for applications such as wear-resistant coatings, diffusion barriers, and gate electrodes for advanced microelectronic devices. Given the industrial importance of HfNx, however, it is surprising how little is known about the properties of this materials system. In this thesis, I present the results of a detailed study on the growth and fundamental properties of epitaxial and polycrystalline HfNx layers as a function of x. In addition, effects of ion-irradiation on the microstructure, texture, and physical properties are also studied in order to develop an understanding of HfNx growth kinetics.; HfNx layers with 0.80 ≤ x ≤ 1.38 grown at 650°C crystallize epitaxially on MgO(001), while films with 1.24 ≤ x ≤ 1.50 contain a N-rich second phase. The room-temperature resistivity, hardness, elastic modulus, and relaxed lattice parameter of stoichiometric HfN(001) are 14.2 muO-cm, 25.2 GPa, 450 GPa, and 0.4524 nm, respectively. Single-phase HfNx(001) is metallic with a positive temperature coefficient of resistivity (TCR) and a temperature-independent carrier density and is also superconducting with the highest critical temperature, 9.18 K, obtained for stoichiometric layers. However, HfNx layers with x ≥ 1.38 exhibit negative TCRs, no superconducting transition, and decreases in H and E.; The phase-compositions obtained in HfNx grown on SiO 2 at 350°C are alpha-Hf:N (x ≤ 0.6); multiphases (0.6 ≤ x ≤ 0.9); delta-HfN single-phase (0.9 ≤ x ≤ 1.3); and mixtures of delta-HfN and higher nitrides (x ≥ 1.3). HfNx layers with 0.9 ≤ x ≤ 1.2 grown under mild ion-irradiation are underdense with mixed orientation, low in-plane stress, and rough surfaces due to limited adatom mobilities resulting in kinetic roughening during film growth. However, the use of intense ion-irradiation leads to dense HfNx layers with 111 texture, compressive in-plane stress, and smooth surfaces due to enhanced adatom surface mobilities and thus, lower electrical resistivity and higher hardness are obtained. For HfNx layers with 1.2 ≤ x ≤ 1.6, the correspondingly higher steady state atomic N surface coverages during deposition alter growth kinetics in favor of 001 texture with a fully dense structure and compressive in-plane stress. |
