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Transport electron/phonon coupling parameters and Eliashberg spectral functions alpha F-2(tr)((h) over bar omega) 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 andlt; T andlt; 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 lambda(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 lambda(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 andlt; 4 K for CeN. The Eliashberg spectral function describes the strength and energy spectrum of electron/phonon coupling in conventional superconductors. Spectral peaks in alpha F-2(andlt;(h)over barandgt;omega), corresponding to regions in energy-space for which electrons couple to acoustic (h) over bar omega(ac) and optical (h) over bar omega(op) phonon modes, are centered at (h) over bar omega(ac) = 33 and (h) over bar omega(op) = 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 +/- 0.1 for all four nitrides, indicating similar electron/phonon coupling strengths alpha(tr)((h) over bar omega) for both modes., Funding Agencies|Swedish Research Council (VR)||Swedish Government Strategic Research Area Grant in Materials Science (SFO Mat-LiU) on Advanced Functional Materials

Transport electron/phonon coupling parameters and Eliashberg spectral functions alpha F-2(tr)((h) over bar omega) 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 andlt; T andlt; 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 lambda(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 lambda(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 andlt; 4 K for CeN. The Eliashberg spectral function describes the strength and energy spectrum of electron/phonon coupling in conventional superconductors. Spectral peaks in alpha F-2(andlt;(h)over barandgt;omega), corresponding to regions in energy-space for which electrons couple to acoustic (h) over bar omega(ac) and optical (h) over bar omega(op) phonon modes, are centered at (h) over bar omega(ac) = 33 and (h) over bar omega(op) = 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 +/- 0.1 for all four nitrides, indicating similar electron/phonon coupling strengths alpha(tr)((h) over bar omega) for both modes., Funding Agencies|Swedish Research Council (VR)||Swedish Government Strategic Research Area Grant in Materials Science (SFO Mat-LiU) on Advanced Functional Materials

Transport electron/phonon coupling parameters and Eliashberg spectral functions alpha F-2(tr)((h) over bar omega) 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 andlt; T andlt; 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 lambda(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 lambda(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 andlt; 4 K for CeN. The Eliashberg spectral function describes the strength and energy spectrum of electron/phonon coupling in conventional superconductors. Spectral peaks in alpha F-2(andlt;(h)over barandgt;omega), corresponding to regions in energy-space for which electrons couple to acoustic (h) over bar omega(ac) and optical (h) over bar omega(op) phonon modes, are centered at (h) over bar omega(ac) = 33 and (h) over bar omega(op) = 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 +/- 0.1 for all four nitrides, indicating similar electron/phonon coupling strengths alpha(tr)((h) over bar omega) for both modes., Funding Agencies|Swedish Research Council (VR)||Swedish Government Strategic Research Area Grant in Materials Science (SFO Mat-LiU) on Advanced Functional Materials

Single-crystal ZrN films, 830 nm thick, are grown on MgO(001) at 450 degrees C by magnetically unbalanced reactive magnetron sputtering. The combination of high-resolution x-ray diffraction reciprocal lattice maps, high-resolution cross-sectional transmission electron microscopy, and selected-area electron diffraction shows that ZrN grows epitaxially on MgO(001) with a cube-on-cube orientational relationship, (001)(ZrN)parallel to(001)(MgO) and [100](ZrN)parallel to[100](MgO). The layers are essentially fully relaxed with a lattice parameter of 0.4575 nm, in good agreement with reported results for bulk ZrN crystals. X-ray reflectivity results reveal that the films are completely dense with smooth surfaces (roughness = 1.3 nm, consistent with atomic-force microscopy analyses). Based on temperature-dependent electronic transport measurements, epitaxial ZrN/MgO(001) layers have a room-temperature resistivity rho(300K) of 12.0 mu Omega-cm, a temperature coefficient of resistivity between 100 and 300K of 5.6 x 10(-8) Omega-cm K-1, a residual resistivity rho(o) below 30K of 0.78 mu Omega-cm (corresponding to a residual resistivity ratio rho(300K)/rho(15K) = 15), and the layers exhibit a superconducting transition temperature of 10.4 K. The relatively high residual resistivity ratio, combined with long in-plane and out-of-plane x-ray coherence lengths, xi(parallel to) = 18 nm and xi(perpendicular to) = 161 nm, indicates high crystalline quality with low mosaicity. The reflectance of ZrN(001), as determined by variable-angle spectroscopic ellipsometry, decreases slowly from 95% at 1 eV to 90% at 2 eV with a reflectance edge at 3.04 eV. Interband transitions dominate the dielectric response above 2 eV. The ZrN(001) nanoindentation hardness and modulus are 22.7 +/- 1.7 and 450 +/- 25 GPa., Funding Agencies|Swedish Research Council (VR)||Swedish Government Strategic Research Area Grant in Materials Science (SFO Mat-LiU) on Advanced Functional Materials

Transport electron/phonon coupling parameters and Eliashberg spectral functions alpha F-2(tr)((h) over bar omega) 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 andlt; T andlt; 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 lambda(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 lambda(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 andlt; 4 K for CeN. The Eliashberg spectral function describes the strength and energy spectrum of electron/phonon coupling in conventional superconductors. Spectral peaks in alpha F-2(andlt;(h)over barandgt;omega), corresponding to regions in energy-space for which electrons couple to acoustic (h) over bar omega(ac) and optical (h) over bar omega(op) phonon modes, are centered at (h) over bar omega(ac) = 33 and (h) over bar omega(op) = 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 +/- 0.1 for all four nitrides, indicating similar electron/phonon coupling strengths alpha(tr)((h) over bar omega) for both modes., Funding Agencies|Swedish Research Council (VR)||Swedish Government Strategic Research Area Grant in Materials Science (SFO Mat-LiU) on Advanced Functional Materials

Transport electron/phonon coupling parameters and Eliashberg spectral functions alpha F-2(tr)((h) over bar omega) 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 andlt; T andlt; 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 lambda(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 lambda(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 andlt; 4 K for CeN. The Eliashberg spectral function describes the strength and energy spectrum of electron/phonon coupling in conventional superconductors. Spectral peaks in alpha F-2(andlt;(h)over barandgt;omega), corresponding to regions in energy-space for which electrons couple to acoustic (h) over bar omega(ac) and optical (h) over bar omega(op) phonon modes, are centered at (h) over bar omega(ac) = 33 and (h) over bar omega(op) = 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 +/- 0.1 for all four nitrides, indicating similar electron/phonon coupling strengths alpha(tr)((h) over bar omega) for both modes., Funding Agencies|Swedish Research Council (VR)||Swedish Government Strategic Research Area Grant in Materials Science (SFO Mat-LiU) on Advanced Functional Materials

The AlN incorporation probability in single crystal Hf-1 (-) xAlxN(0 0 1) layers is controllably adjusted between similar to 0% and 100% by varying the ion energy (E-i) incident at the growing film over a narrow range, 10-40 eV. The layers are grown on MgO(0 0 1) at 450 degrees C using ultrahigh vacuum magnetically unbalanced reactive magnetron sputtering from a Hf0.7Al0.3 alloy target in a 5%-N-2/Ar atmosphere at a total pressure of 20 mTorr (2.67 Pa). The ion to metal flux ratio incident at the growing film is constant at 8. Epitaxial film compositions vary from x = 0.30 with E-i = 10 eV, to 0.27 with E-i = 20 eV, 0.17 with E-i = 30 eV, and andlt;= 0.002 with E-i andgt;= 40 eV. Thus, the AlN incorporation probability decreases by greater than two orders of magnitude. This extraordinary range in real-time manipulation of film chemistry during deposition is due to the efficient resputtering of deposited Al atoms (27 amu) by Ar+ ions (40 amu) neutralized and backscattered from heavy Hf atoms (178.5 amu) in the film. This provides a new reaction pathway to synthesize, at high deposition rates, compositionally complex heterostructures, multilayers, and superlattices with abrupt interfaces from a single alloy target by controllably switching E-i. For multilayer and superlattice structures, the choice of E-i value determines the layer composition and the switching periods control the individual layer thickness.

Nanostructured materials—the subject of much of contemporary materials research—are defined by internal interfaces, the nature of which is largely unknown. Yet, the interfaces determine the properties of nanocomposites and nanolaminates. An example is nanocomposites with extreme hardness70–90 GPa, which is of the order of, or higher than, diamond. The Ti-Si-N system, in particular, is attracting attention for the synthesis of such superhard materials. In this case, the nanocomposite structure consists of TiN nanocrystallites encapsulated in a fully percolated SiNx “tissue phase” (1 to 2 monolayers thick) that is assumed to be amorphous. Here, we show that the interfacial tissue phase can be crystalline, and even epitaxial with complex surface reconstructions. Using in situ structural analyses combined with ab initio calculations, we find that SiNx layers grow epitaxially, giving rise to strong interfacial bonding, on both TiN(001) and TiN(111) surfaces. In addition, TiN overlayers grow epitaxially on SiNx/TiN(001) bilayers in nanolaminate structures. These results provide insight into the development of design rules for new nanostructured materials.