Electron/phonon coupling in group-IV transition-metal and rare-earth nitrides

Abstract

Transport electron/phonon coupling parameters and Eliashberg spectral functions a tr 2 F( hx) are determined for group-IV transition-metal (TM) nitrides TiN, ZrN, and HfN, and the rare-earth (RE) nitride CeN using an inversion procedure based upon temperature-dependent (4 < T < 300 K) resistivity measurements of high-crystalline-quality stoichiometric epitaxial films grown on MgO(001) by magnetically-unbalanced reactive magnetron sputtering. Transport electron/phonon coupling parameters k tr vary from 1.11 for ZrN to 0.82 for HfN, 0.73 for TiN, and 0.44 for CeN. The small variation in k tr among the TM nitrides and the weak coupling in CeN are consistent with measured superconducting transition temperatures 10.4 (ZrN), 9.18 (HfN), 5.35 (TiN), and <4 K for CeN. The Eliashberg spectral function describes the strength and energy spectrum of electron/phonon coupling in conventional superconductors. Spectral peaks in a 2 F( hx), corresponding to regions in energy-space for which electrons couple to acoustic hx ac and optical hx op phonon modes, are centered at hx ac ¼ 33 and hx op ¼ 57 meV for TiN, 25 and 60 meV for ZrN, 18 and 64 meV for HfN, and 21 and 39 meV for CeN. The acoustic modes soften with increasing cation mass; optical mode energies remain approximately constant for the TM nitrides, but are significantly lower for the RE nitride due to a lower interatomic force constant. Optical/acoustic peak-intensity ratios are 1.15 6 0.1 for all four nitrides, indicating similar electron/phonon coupling strengths a tr ( hx) for both modes. V C 2013 AIP Publishing LLC. [http://dx

Nonequilibrium ab initio molecular dynamics determination of Ti monovacancy migration rates in B1 TiN

“…Transition-metal (TM) nitride refractory ceramics possess outstanding physical and mechanical properties, including extreme hardness [1][2][3], high toughness [4][5][6], thermal stability [7,8], chemical inertness [9,10], and good electrical conductivity [2,11], which renders them important for a large variety of applications ranging from wear-resistant protective coatings on tools employed in industrial machining [12,13] to diffusion barrier in electronic devices [14,15].…”

First principle calculation of structural, electronic and elastic properties of rare earth nitride

“…The RENs posses partially filled f-electron orbital. All the RENs crystallize into the NaCl rock salt structure at normal temperature and pressure [1][2][3][4].…”

Ab Initio Molecular Dynamics Simulations of Nitrogen/VN(001) Surface Reactions: Vacancy-Catalyzed N2 Dissociative Chemisorption, N Adatom Migration, and N2 Desorption

“…2,12 Currently, these materials are widely employed as wear-resistant protective coatings on cutting tools 13 and engine components, 14 diffusion barrier in microelectronic devices, [15][16][17][18] and active layers in energy-harvesting thermoelectric and piezoelectric devices. 19,20 Recently, refractory TM nitrides have been suggested as highly promising candidates to replace noble metals in plasmonic devices for high-temperature optoelectronic applications.…”