Epitaxial and polycrystalline HfN{sub x} (0.8{<=}x{<=}1.5) layers on MgO(001): Film growth and physical properties

Journal Article · Fri Apr 15 04:00:00 EDT 2005 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.1870097· OSTI ID:20668308

Seo, H -S; Lee, T -Y; Petrov, I; Greene, J E; Gall, D ^[1]

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1. Frederick Seitz Materials Research Laboratory and Materials Science Department, University of Illinois, 104 South Goodwin, Urbana, Illinois 61801 (United States)

While many transition metal (TM) 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{sub x} layers, with 0.80{<=}x{<=}1.50, deposited on MgO(001) by ultrahigh vacuum reactive magnetron sputtering at 650 deg. C in mixed N{sub 2}/Ar discharges. HfN{sub x} layers with 0.80{<=}x{<=}1.20 crystallize in the B1-NaCl structure with a cube-on-cube epitaxial relationship to the MgO(001) substrate, while films with 1.24{<=}x{<=}1.50 contain a N-rich second phase. The relaxed bulk lattice parameter of HfN{sub x}(001) 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 {rho} of stoichiometric HfN(001) is 14.2 {mu}{omega} cm and {rho}(x) increases with both increasing and decreasing x to 140 {mu}{omega} cm with x=0.80 and 26.4 {mu}{omega} cm with x=1.20. The hardness H and elastic modulus E of HfN(001) are 25.2 and 450 GPa, respectively. H(x) initially increases for both over- and understoichiometric layers due to defect-induced hardening, while E(x) remains essentially constant. Single-phase HfN{sub x}(001) is metallic with a positive temperature coefficient of resistivity (TCR) 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, {rho} ranges from 59.8 {mu}{omega} cm with x=1.24 to 2710 {mu}{omega} cm with x=1.50. TCR becomes positive with x{>=}1.38, no superconducting transition is observed, and both H and E decrease.

• OSTI ID: 20668308
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 8 Vol. 97; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CARRIER DENSITY
COATINGS
CRITICAL TEMPERATURE
DEPOSITION
DIFFUSION BARRIERS
EPITAXY
HAFNIUM NITRIDES
HARDENING
LATTICE PARAMETERS
MAGNESIUM OXIDES
POLYCRYSTALS
PRESSURE RANGE GIGA PA
SPUTTERING
STOICHIOMETRY
TANTALUM NITRIDES
TEMPERATURE COEFFICIENT
TEMPERATURE RANGE 0273-0400 K
TITANIUM NITRIDES
WEAR RESISTANCE
ZIRCONIUM NITRIDES