Articles you may be interested inPhysical properties of epitaxial ZrN/MgO(001) layers grown by reactive magnetron sputtering J. Vac. Sci. Technol. A 31, 061516 (2013); 10.1116/1.4825349Effect of off stoichiometry on Raman scattering from epitaxial and polycrystalline HfN x ( 0.85 ≤ x ≤ 1.50 ) grown on MgO (001) While many transition metal ͑TM͒ nitrides-including TiN, ZrN, and TaN-have been widely studied and are currently used as hard wear-resistant coatings, diffusion barriers, and optical coatings, little is known about a related TM nitride, HfN. Here, we report the results of a systematic investigation of the growth and physical properties of HfN x layers, with 0.80ഛ x ഛ 1.50, deposited on MgO͑001͒ by ultrahigh vacuum reactive magnetron sputtering at 650°C in mixed N 2 /Ar discharges. HfN x layers with 0.80ഛ x ഛ 1.20 crystallize in the B1-NaCl structure with a cube-on-cube epitaxial relationship to the MgO͑001͒ substrate, while films with 1.24ഛ x ഛ 1.50 contain a N-rich second phase. The relaxed bulk lattice parameter of HfN x ͑001͒ decreases only slightly with increasing N / Hf ratio, ranging from 0.4543 nm with x = 0.80 to 0.4517 nm with x = 1.20. The room-temperature resistivity of stoichiometric HfN͑001͒ is 14.2 ⍀ cm and ͑x͒ increases with both increasing and decreasing x to 140 ⍀ cm with x = 0.80 and 26.4 ⍀ cm with x = 1.20. The hardness H and elastic modulus E of HfN͑001͒ are 25.2 and 450 GPa, respectively. H͑x͒ initially increases for both over-and understoichiometric layers due to defect-induced hardening, while E͑x͒ remains essentially constant. Single-phase HfN x ͑001͒ is metallic with a positive temperature coefficient of resistivity ͑TCR͒ between 50 and 300 K and a temperature-independent carrier density. It is also superconducting with the highest critical temperature, 9.18 K, obtained for layers with x = 1.00. In the two phase regime, ranges from 59.8 ⍀ cm with x = 1.24 to 2710 ⍀ cm with x = 1.50. TCR becomes positive with x ജ 1.38, no superconducting transition is observed, and both H and E decrease.

While NaCl-structure transition-metal nitrides have been widely studied over the past two decades, little is known about the corresponding NaCl-structure rare-earth nitrides. Polycrystalline CeN, for example, has been reported by different groups to be both a wide band-gap semiconductor and a metal. To address this controversy, we have grown epitaxial CeN layers on MgO(001) and measured their physical properties. The films were grown at 700 °C by ultrahigh vacuum reactive magnetron sputter deposition in mixed Ar/N2 discharges maintained at 4 mTorr (0.53 Pa). X-ray diffraction and transmission electron microscopy results establish the film/substrate epitaxial relationship as cube-on-cube, (001)CeN‖(001)MgO with [100]CeN‖[100]MgO, while Rutherford backscattering spectroscopy shows that the layers are stoichiometric with N/Ce=0.99±0.02. CeN is metallic with a positive temperature coefficient of resistivity and a temperature-independent carrier concentration, as determined by Hall effect measurements, of 2.8±0.2×1022 cm−3 with a room temperature mobility of 0.31 cm2 V−1 s−1. At temperatures between 2 and 50 K, the resistivity is limited by defect scattering and remains constant at 29 μΩ cm, while at higher temperatures it increases linearly, limited primarily by phonon scattering, to reach a room-temperature value of 68.5 μΩ cm. The hardness and elastic modulus of CeN(001) were determined from nanoindentation measurements to be 15.0±0.9 and 330±16 GPa.