AVS 47th International Symposium
    Surface Engineering Tuesday Sessions
       Session SE-TuM

Paper SE-TuM2
Epitaxial Growth of Metastable B1-NaCl-Structure TaN@sub x@ on MgO(001) by Ultrahigh Vacuum Reactive Magnetron Sputter Deposition

Tuesday, October 3, 2000, 8:40 am, Room 201

Session: Interface Engineering and Graded Films: Structure and Characterization
Presenter: C.-S. Shin, University of Illinois
Authors: C.-S. Shin, University of Illinois
D. Gall, University of Illinois
J.E. Greene, University of Illinois
I. Petrov, University of Illinois
Correspondent: Click to Email
Metastable B1-NaCl-structure TaN@sub x@ (x = 1-1.3) layers, with thicknesses 0.25 to 0.5 @micro@m, were epitaxially grown on MgO(001) at temperatures T@sub s@ between 600 and 700 °C by ultra-high-vacuum reactive magnetron sputtering in N@sub 2@/Ar mixtures. X-ray diffraction and transmission electron microscopy results show that the epitaxial relationship is cube-on-cube, (001)@sub TaN@||(001)@sub MgO@ with [100]@sub TaN@||[100]@sub MgO@. TaN@sub x@ layers grown at T@sub s@@>=@ 700 °C undergo a transition from the metastable NaCl structure to the thermodynamically-stable hexagonal phase. NaCl-structure TaN@sub x@ layers with x = 1-1.22 exhibit a nearly constant resistivity of 225 @micro@@OHM@-cm with hardness (H) and elastic modulus (G) values, determined by nanoindentation, of 31±0.9 and 457±16 GPa, respectively. Higher N/Ta ratios lead to an increase in @rho@ and a decrease in H and G. All cubic TaN@sub x@ layers exhibit negative temperature coefficients of resistivity between 20 and 400 K due to weak carrier localization. TaN@sub x@ is superconducting with the highest critical temperature, 8.45 K, obtained when x is close to 1.