The electron mean free path k and carrier relaxation time s of the twenty most conductive elemental metals are determined by numerical integration over the Fermi surface obtained from first-principles, using constant k or s approximations and wave-vector dependent Fermi velocities v f (k). The average v f deviates considerably from the free-electron prediction, even for elements with spherical Fermi surfaces including Cu (29% deviation). The calculated product of the bulk resistivity times k indicates that, in the limit of narrow wires, Rh, Ir, and Ni are 2.1, 1.8, and 1.6 times more conductive than Cu, while various metals including Mo, Co, and Ru approximately match the Cu resistivity, suggesting that these metals are promising candidates to replace Cu for narrow interconnect lines. V

Density functional methods were used to calculate binding and diffusion energies of adatoms, molecules, and small clusters on TiN͑001͒ and TiN͑111͒ surfaces in order to isolate the key atomistic processes which determine texture evolution during growth of polycrystalline TiN layers. The surface energy for nonpolar TiN͑001͒, 81 meV/Å 2 , was found to be lower than that of both Nand Ti-terminated TiN͑111͒ polar surfaces, 85 and 346 meV/Å 2. While N 2 molecules are only weakly physisorbed, Ti adatoms form strong bonds with both TiN͑001͒, 3.30 eV, and TiN͑111͒, 10.09 eV. Ti adatom diffusion is fast on ͑001͒, but slow on ͑111͒ surfaces, with calculated energy barriers of 0.35 and 1.74 eV, respectively. The overall results show that growth of 111-oriented grains is favored under conditions typical for reactive sputter deposition. However, the presence of excess atomic N ͑due, for example, to collisionally induced dissociation of energetic N 2 ϩ ions͒ leads to a reduced Ti diffusion length, an enhanced surface island nucleation rate, and a lower chemical potential on the ͑001͒ surface. The combination of these effects results in preferential growth of 001 grains. Thus our results provide an atomistic explanation for the previously reported transition from 111 to 001 texture observed for sputter deposition of TiN in Ar/N 2 mixtures with increasing N 2 partial pressure P N 2 and at constant P N 2 with increasing N 2 ϩ /Ti flux ratios incident at the growing film.

Articles you may be interested inThermoelectric properties of epitaxial ScN films deposited by reactive magnetron sputtering onto MgO(001) substrates J. Appl. Phys. 113, 153704 (2013); 10.1063/1.4801886 Growth of fullerene-like carbon nitride thin solid films by reactive magnetron sputtering; role of low-energy ion irradiation in determining microstructure and mechanical properties J. Appl. Phys. 93, 3002 (2003); 10.1063/1.1538316 Growth of single-crystal CrN on MgO(001): Effects of low-energy ion-irradiation on surface morphological evolution and physical properties Microstructure and electronic properties of the refractory semiconductor ScN grown on MgO(001) by ultra-highvacuum reactive magnetron sputter depositionScN layers, 345 nm thick, were grown on MgO͑001͒ substrates at 750°C by ultrahigh-vacuum reactive magnetron sputter deposition in pure N 2 discharges at 5 mTorr. The N 2 ϩ to Sc ratio incident at the substrate and growing film was maintained constant at 14, while the ion energy E N 2 ϩ was varied from 13 to 50 eV. All films were stoichiometric with N/Sc ratios of 1.00Ϯ0.02. However, microstructural and surface morphological evolution were found to depend strongly on E N 2 ϩ . The nucleation and initial growth stages of ScN films deposited with E N 2 ϩϭ 13 eV are dominated by the formation of 111-and 002-oriented islands, but preferred orientation rapidly evolves toward a purely 111 texture by a film thickness of Ӎ50 nm as 002 grains grow out of existence in a kinetically limited competitive growth mode. In distinct contrast, films deposited with E N 2 ϩ ϭ20 eV grow in a cube-on-cube epitaxial relationship with the substrate and exhibit no indication of 111-oriented grains, even in the earliest stages. Increasing E N 2 ϩ to 50 eV still results in epitaxial layers, but with high in-plane compressive stress and the presence of N 2 gas bubbles. All epitaxial layers contain rectangular nanopipes Ӎ1 nm wide and aligned along the growth direction. The nanopipes result from atomic shadowing near the bottom of a periodic array of surface cusps which form along orthogonal ͗100͘ directions due to kinetic roughening during growth. The hardness H and elastic modulus E of the epitaxial ScN͑001͒ layer grown with E N 2 ϩϭ 20 eV are 21.1Ϯ1.1 and 356Ϯ18 GPa, respectively. H and E increase ͑decrease͒ with increasing ͑decreasing͒ E N 2 ϩ .

This work presents a proposed mechanism for fabricating Y-shaped nanorods, demonstrates the feasibility of the proposal through classical molecular dynamics simulations, and validates the simulations through magnetron sputter deposition experiments. The proposed mechanism relies primarily on the formation of stacking faults during deposition and to a lesser degree on diffusion kinetics and geometrical shadowing. Applications of the proposed mechanism may enable the design of nanorod arrays with controlled branching.

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