Ivan Petrov

Metal versus rare-gas ion irradiation during Ti1−xAlxN film growth by hybrid high power pulsed magnetron/dc magnetron co-sputtering using synchronized pulsed substrate bias

Metastable NaCl-structure Ti1-xAlxN is employed as a model system to probe the effects of metal versus rare-gas ion irradiation during film growth using reactive high-power pulsed magnetron sputter ...

Toughness enhancement in hard ceramic thin films by alloy design

Hardness is an essential property for a wide range of applications. However, hardness alone, typically accompanied by brittleness, is not sufficient to prevent failure in ceramic films exposed to h ...

Configurational disorder effects on adatom mobilities on Ti1-xAlxN(001) surfaces from first principles

We use metastable NaCl-structure Ti0.5Al0.5N alloys to probe effects of configurational disorder on adatom surface diffusion dynamics which control phase stability and nanostructural evolution during film growth. First-principles calculations were employed to obtain potential energy maps of Ti and Al adsorption on an ordered TiN(001) reference surface and a disordered Ti0.5Al0.5N(001) solid-solution surface. The energetics of adatom migration on these surfaces are determined and compared in order to isolate effects of configurational disorder. The results show that alloy surface disorder dramatically reduces Ti adatom mobilities. Al adatoms, in sharp contrast, experience only small disorder-induced differences in migration dynamics.

Novel strategy for low-temperature, high-rate growth of dense, hard, and stress-free refractory ceramic thin films

Growth of fully dense refractory thin films by means of physical vapor deposition (PVD) requires elevated temperatures Ts to ensure sufficient adatom mobilities. Films grown with no external heating are underdense, as demonstrated by the open voids visible in cross-sectional transmission electron microscopy images and by x-ray reflectivity results; thus, the layers exhibit low nanoindentation hardness and elastic modulus values. Ion bombardment of the growing film surface is often used to enhance densification; however, the required ion energies typically extract a steep price in the form of residual rare-gas-ion-induced compressive stress. Here, the authors propose a PVD strategy for the growth of dense, hard, and stress-free refractory thin films at low temperatures; that is, with no external heating. The authors use TiN as a model ceramic materials system and employ hybrid high-power pulsed and dc magnetron co-sputtering (HIPIMS and DCMS) in Ar/N2 mixtures to grow dilute Ti1−xTaxN alloys on Si(001) sub...

Elastic constants, Poisson ratios, and the elastic anisotropy of VN(001), (011), and (111) epitaxial layers grown by reactive magnetron sputter deposition

Elastic constants are determined for single-crystal stoichiometric NaCl-structure VN(001), VN(011), and VN(111) epitaxial layers grown by magnetically unbalanced reactive magnetron sputter deposition on 001-, 011-, and 111-oriented MgO substrates at 430u2009°C. The relaxed lattice parameter aou2009=u20090.4134u2009±u20090.0004u2009nm, obtained from high-resolution reciprocal space maps, and the mass density ρu2009=u20096.1u2009g/cm3, determined from the combination of Rutherford backscattering spectroscopy and film thickness measurements, of the VN layers are both in good agreement with reported values for bulk crystals. Sub-picosecond ultrasonic optical pump/probe techniques are used to generate and detect VN longitudinal sound waves with measured velocities v001u2009=u20099.8u2009±u20090.3, v011u2009=u20099.1u2009±u20090.3, and v111u2009=u20099.1u2009±u20090.3u2009km/s. The VN c11 elastic constant is determined from the sound wave velocity measurements as 585u2009±u200930u2009GPa; the c44 elastic constant, 126u2009±u20093u2009GPa, is obtained from surface acoustic wave measurements. From the combination of c11, c44, vhkl, and ρ we obtain the VN c12 elastic constant 178u2009±u200933u2009GPa, the VN elastic anisotropy Au2009=u20090.62, the isotropic Poisson ratio νu2009=u20090.29, and the anisotropic Poisson ratios ν001u2009=u20090.23, ν011u2009=u20090.30, and ν111u2009=u20090.29.

Nanolabyrinthine ZrAlN thin films by self-organization of interwoven single-crystal cubic and hexagonal phases

Self-organization on the nanometer scale is a trend in materials research. Thermodynamic driving forces may, for example, yield chessboard patterns in metal alloys [Y. Ni and A. G. Khachaturyan, Nature Mater. 8, 410–414 (2009)]10.1038/nmat2431 or nitrides [P. H. Mayrhofer, A. Horling, L. Karlsson, J. Sjolen, T. Larsson, and C. Mitterer, Appl. Phys. Lett. 83, 2049 (2003)]10.1063/1.1608464 during spinodal decomposition. Here, we explore the ZrN-AlN system, which has one of the largest positive enthalpies of mixing among the transition metal aluminum nitrides [D. Holec, R. Rachbauer, L. Chen, L. Wang, D. Luefa, and P. H. Mayrhofer, Surf. Coat. Technol. 206, 1698–1704 (2011)10.1016/j.surfcoat.2011.09.019; B. Alling, A. Karimi, and I. Abrikosov, Surf. Coat. Technol. 203, 883–886 (2008)]10.1016/j.surfcoat.2008.08.027. Surprisingly, a highly regular superhard (36 GPa) two-dimensional nanolabyrinthine structure of two intergrown single crystal phases evolves during magnetron sputter thin film synthesis of Zr0.64A...

Large-scale molecular dynamics simulations of TiN/TiN(001) epitaxial film growth

Large-scale classical molecular dynamics simulations of epitaxial TiN/TiN(001) thin film growth at 1200K are carried out using incident flux ratios N/Ti -1, 2, and 4. The films are analyzed as a fu ...

Enhanced Ti0.84Ta0.16N diffusion barriers, grown by a hybrid sputtering technique with no substrate heating, between Si (001) wafers and Cu overlayers

We compare the performance of conventional DC magnetron sputter-deposited (DCMS) TiN diffusion barriers between Cu overlayers and Si(001) substrates with Ti0.84Ta0.16N barriers grown by hybrid DCMS/high-power impulse magnetron sputtering (HiPIMS) with substrate bias synchronized to the metal-rich portion of each pulse. DCMS power is applied to a Ti target, and HiPIMS applied to Ta. No external substrate heating is used in either the DCMS or hybrid DCMS/HiPIMS process in order to meet future industrial thermal-budget requirements. Barrier efficiency in inhibiting Cu diffusion into Si(001) while annealing for 1u2009hour at temperatures between 700 and 900u2009°C is investigated using scanning electron microscopy, X-ray diffraction, four-point-probe sheet resistance measurements, transmission electron microscopy, and energy-dispersive X-ray spectroscopy profiling. Ti0.84Ta0.16N barriers are shown to prevent large-scale Cu diffusion at temperatures up to 900u2009°C, while conventional TiN barriers fail at ≤700u2009°C. The improved performance of the Ti0.84Ta0.16N barrier is due to film densification resulting from HiPIMS pulsed irradiation of the growing film with synchronized Ta ions. The heavy ion bombardment dynamically enhances near-surface atomic mixing during barrier-layer deposition.

Effects of incident N atom kinetic energy on TiN/TiN(001) film growth dynamics: A molecular dynamics investigation

Large-scale classical molecular dynamics simulations of epitaxial TiN/TiN(001) thin film growth at 1200u2009K, a temperature within the optimal range for epitaxial TiN growth, with an incident N-to-Ti flux ratio of four, are carried out using incident N energies ENu2009=u20092 and 10u2009eV and incident Ti energy ETiu2009=u20092u2009eV. To further highlight the effect of EN, we grow a bilayer film with ENu2009=u20092u2009eV initially and then switch to ENu2009=u200910u2009eV. As-deposited layers are analyzed as a function of composition, island-size distribution, island-edge orientation, and vacancy formation. Results show that growth with ENu2009=u20092u2009eV results in films that are globally overstoichiometric with islands bounded by N-terminated polar 110 edges, whereas films grown with ENu2009=u200910u2009eV are flatter and closer to stoichiometric. However, ENu2009=u200910u2009eV layers exhibit local N deficiency leading to the formation of isolated 111-oriented islands. Films grown by changing the incident energy from 2 to 10u2009eV during growth are more compact than those grown entirel...

Effects of surface vibrations on interlayer mass transport: Ab initio molecular dynamics investigation of Ti adatom descent pathways and rates from TiN/TiN(001) islands

We carried out density-functional ab initio molecular dynamics (AIMD) simulations of Ti adatom (