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The present paper proposes a mathematical model for the examination of dynamic processes of a motorvehicle during operation in different regimes. A non-linear mathematical model based on the equations for joint movement of an engine and an operating machine is created in this respect. The behaviour of the system is examined at operating regimes of an internal combustion engine (ICE) during idle running, motor-vehicle starting with clutch engagement, motor-vehicle accelerating at engaged gear. The transitional performance includes the transition of the engine operation from idle running to external frequency characteristics. Developed, accordingly, is a computing programme for analysis of the transitional performance of an ICE during starting at initial state without motion and consecutive acceleration. The changes of the kinematic and ecological parameters of an ICE during its operation in transitional performance are determined and graphically presented.

Stoichiometric HfN layers, with N/Hf=1.0±0.03, were grown on MgO(001) substrates at 650 °C by ultrahigh-vacuum magnetically unbalanced magnetron sputter deposition in mixed N2/Ar discharges at 20 mTorr (2.67 Pa). High-resolution x-ray diffraction ω-2θ and azimuthal φ scans combined with cross-sectional transmission electron microscopy establish that HfN grows epitaxially with a cube-on-cube orientational relationship to the substrate: (001)HfN∥(001)MgO and [100]HfN∥[100]MgO. The layers are fully relaxed at the growth temperature and have a room-temperature bulk lattice constant of 0.4524 nm. Electronic transport measurements show that HfN is metallic with a room-temperature resistivity of 14.2 μΩ cm, an n-type carrier concentration of 4.8×1021 cm−3, and an electron mobility of 86 cm2 V−1 s−1. The resistivity ρ remains constant at 3.5 μΩ cm, limited by defect scattering, between 10 and 50 K, while at higher temperatures ρ increases linearly and is limited primarily by phonon scattering. HfN(001) is also superconducting with a critical temperature of 9.18 K. The hardness and elastic modulus of HfN(001) were determined from nanoindentation measurements to be 25.2±0.7 and 450±9 GPa, respectively.

We have grown single-crystal NaCl-structure δ-TiNx layers with x ranging from 0.67 to 1.00 on MgO(001) at 700 °C by ultra-high-vacuum reactive magnetron sputtering of Ti in mixed Ar/N2 discharges in order to investigate microstructural evolution and the physical properties of TiNx as a function of the N vacancy concentration. High-resolution x-ray diffraction and transmission electron microscopy results show that all layers grow with a cube-on-cube epitaxial relationship to the substrate, (001)TiN∥(001)MgO and [100]TiN∥[100]MgO. The relaxed lattice parameter ao(x) decreases linearly from 4.240 A with x=1.00 to 4.226 A with x=0.67. Stoichiometric TiN(001) layers are fully relaxed at the growth temperature while layers with 0.67⩽x⩽0.92 are fully coherent with their substrates. Surface morphologies vary dramatically with x. TiNx(001) layers with x=0.67–0.82 have very flat surfaces arising from large cation surface diffusion lengths approaching values corresponding to step flow. However, the surfaces of the TiN0.92(001) and TiN1.00(001) layers, which were grown at higher N2 partial pressures, consist of a periodic two-domain ripple structure along the 〈110〉 directions due to kinetic roughening associated with lower cation surface mobilities resulting from higher steady state N coverages. TiN1.0(001) layers grown in pure N2 exhibit growth mounds that are predominantly square with edges aligned along the 〈110〉 directions. The room-temperature resistivity, 13 μΩ cm with x=1.00, increases from 52 μΩ cm for TiNx(001) layers with x=0.92 to 192 μΩ cm with x=0.67, due primarily to increased carrier scattering from N vacancies.

While NaCl-structure transition-metal nitrides have been widely studied over the past two decades, little is known about the corresponding NaCl-structure rare-earth nitrides. Polycrystalline CeN, for example, has been reported by different groups to be both a wide band-gap semiconductor and a metal. To address this controversy, we have grown epitaxial CeN layers on MgO(001) and measured their physical properties. The films were grown at 700 °C by ultrahigh vacuum reactive magnetron sputter deposition in mixed Ar/N2 discharges maintained at 4 mTorr (0.53 Pa). X-ray diffraction and transmission electron microscopy results establish the film/substrate epitaxial relationship as cube-on-cube, (001)CeN‖(001)MgO with [100]CeN‖[100]MgO, while Rutherford backscattering spectroscopy shows that the layers are stoichiometric with N/Ce=0.99±0.02. CeN is metallic with a positive temperature coefficient of resistivity and a temperature-independent carrier concentration, as determined by Hall effect measurements, of 2.8±...

Density functional methods were used to calculate binding and diffusion energies of adatoms, molecules, and small clusters on TiN(001) and TiN(111) surfaces in order to isolate the key atomistic processes which determine texture evolution during growth of polycrystalline TiN layers. The surface energy for nonpolar TiN(001), 81 meV/A2, was found to be lower than that of both N- and Ti-terminated TiN(111) polar surfaces, 85 and 346 meV/A2. While N2 molecules are only weakly physisorbed, Ti adatoms form strong bonds with both TiN(001), 3.30 eV, and TiN(111), 10.09 eV. Ti adatom diffusion is fast on (001), but slow on (111) 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 N2+ ions) leads to a reduced Ti diffusion length, an enhanced surface island nucleation rate, and a lower chemical potential on the (001) 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/N2 mixtures with increasing N2 partial pressure PN2 and at constant PN2 with increasing N2+/Ti flux ratios incident at the growing film.

We investigate the effect of N vacancies on the mechanical properties of epitaxial δ-TiNx(001) layers with x=0.67–1.0. The relaxed lattice parameter increases linearly with x in good agreement with ab initio density functional calculations, indicating that deviations from stoichiometry are entirely due to anion vacancies. Hardness values increase continuously, while the elastic modulus decreases with increasing N-vacancy concentration. We attribute the observed vacancy hardening to a reduced dislocation mobility arising from an increase in the rate-limiting activation energy for cation migration.

We have investigated the effects of low-energy ion irradiation on texture evolution during growth of B1–NaCl-structure polycrystalline δ-TaN layers on SiO2 by ultra-high-vacuum reactive magnetron sputter deposition at 350 °C in mixed Ar+15%N2 discharges. In parallel sets of experiments, the ion-to-metal flux ratio Ji/JTa was varied from 1.3 to 10.7 while maintaining the incident ion energy Ei constant at 20 eV, and Ei was varied from 8.5 to 30 eV with Ji/JTa=10.7. All TaN layers, irrespective of Ji/JTa or Ei, were overstoichiometric with N/Ta=1.13±0.03. Layers grown with Ei=30 eV are multiphase consisting of hexagonal e-TaN and δ-TaN, while those grown with Ei⩽20 eV are single-phase δ-TaN. With Ei=8.5 eV, the δ-TaN layers have a mixed 111/002/022/113 texture, even for film thicknesses t up to 500 nm. In contrast, δ-TaN layers deposited with Ei=20 eV initially exhibit competitive texture evolution until a single texture dominates at t≳200 nm. The preferred orientation of 500-nm-thick Ei=20 eV layers can be...

We show that surface evolution resulting from the deposition of discrete particles is intrinsically different from that produced by continuum processes. The atomistic effects have major consequences, even when observed at macroscopic length scales. We have elucidated some of the atomistic effects by comparing: (i) numerical simulations of thin film deposition using the continuum model, (ii) atomistic (Monte Carlo) models, and (iii) experiments on the sputter deposition of Ta onto a substrate containing etched vias. We have therefore developed a continuum model which incorporates finite atomic length scales. The model incorporates effects of atomic interactions, which lead to the capture of impinging atoms that pass near a point on the film. This capture effect results in “breadloafing” at sharp convex corners where the curvature is high. We have validated our model in idealized two-dimensional simulations and obtained improved qualitative agreement with both experiment and Monte Carlo atomistic simulation...

B1–NaCl-structure CrN(001) layers were grown on MgO(001) at 600 °C by ultrahigh vacuum reactive magnetron sputter deposition in pure N2 discharges. X-ray diffraction analyses establish the epitaxial relationship as cube-on-cube, (001)CrN∥(001)MgO with [100]CrN∥[100]MgO, while temperature-dependent measurements show that the previously reported phase transition to the orthorhombic Pnma structure is, due to epitaxial constraints, absent in our layers. The resistivity increases with decreasing temperature, from 0.028 Ω cm at 400 K to 271 Ω cm at 20 K, indicating semiconducting behavior with hopping conduction. Optical absorption is low (α

CrN layers, 0.5 ╡m thick, were grown on MgO(001) at Ts=570-775░C by ultrahigh vacuum magnetically unbalanced magnetron sputter deposition in pure N2 discharges at 20 mTorr. Layers grown at Ts=700░C ...

Single-crystal TiN(111) layers, 45 nm thick, were grown on MgO(111) by ultrahigh vacuum reactive magnetron sputter deposition in pure N2 discharges at Ts=700 °C. Epitaxial Al(111) overlayers, 160 nm thick, were then deposited at Ts=100 °C in Ar without breaking vacuum. Interfacial reactions and changes in bilayer microstructure due to annealing at 620 and 650 °C were investigated using x-ray diffraction and transmission electron microscopy (TEM). The interfacial regions of samples annealed at 620 °C consist of continuous ≃7-nm-thick epitaxial wurtzite-structure AlN(0001) layers containing a high density of stacking faults, with ≃22 nm thick tetragonal Al3Ti(112) overlayers. Surprisingly, samples annealed at the higher temperature are more stable against Al3Ti formation. TEM analyses of bilayers annealed at 650 °C (10 °C below the Al melting point!) reveal only the self-limited growth of an ≃3-nm-thick interfacial layer of perfect smooth epitaxial wurtzite-structure AlN(0001) which serves as an extremely e...

Single crystalline Sc1−xTixN layers, with compositions spanning the entire range (0⩽x⩽1), were grown on MgO(001) by ultrahigh vacuum reactive magnetron sputter deposition at 750 °C. Optical transmission and reflectivity spectra are well described by a Drude–Lorentz model. The optical carrier density N* increases linearly from 1.0×1021 for ScN to 4.6×1022 cm−3 for TiN while the room-temperature electrical resistivity ρ300K varies by more than 2 orders of magnitude, from 2×10−3 Ω cm for ScN to 13 μΩ cm for TiN. ρ300K agrees well with optically determined resistivity values for alloys with compositions up to x=0.66, corresponding to the onset of electron filling in the second and third conduction bands. We calculated ScN and TiN band structures by ab initio density functional methods and used the results to simulate the field responses of free carriers in the Sc1−xTixN layers. From this, we determined, in combination with the measured temperature dependence of the resistivity, the low-temperature carrier rel...

Epitaxial metastable Ge1−yCy alloy layers with y⩽0.02 were grown on Ge(001) at temperatures Ts=200–550 °C using hyperthermal Ge and C beams with average energies of 16 and 24 eV, respectively, in order to investigate C incorporation pathways in the Ge lattice. High-resolution reciprocal lattice maps show that all as-deposited alloy layers are fully coherent with the substrate. Layers grown at Ts⩽350 °C are in compression due to higher C concentrations in interstitial than in substitutional sites. The compressive strain decreases (i.e., the substitutional C concentration increases) with increasing Ts within this temperature range. At higher growth temperatures, as-deposited alloys are nearly strain free since the majority of the incorporated C is trapped at extended defects. Annealing the Ge1−yCy layers at Ta=450 and 550 °C leads to a significant increase, proportional to the strain in the as-deposited films, in compressive strain. Further annealing at Ta=650 °C results in the formation of dislocation loops which act as sinks for interstitial and substitutional C atoms and thus relieves residual macroscopic strain. Finally, we show that the large compressive strain associated with interstitial C atoms must be accounted for in order to determine the total incorporated C fraction from diffraction analyses.

Highly textured epitaxial metallizations will be required for the next generation of devices with the main driving force being a reduction in electromigration. Herein a model system of 190 nm of Al on a 140 nm layer of W grown on MgO 〈00l〉 substrates was studied. The W layer was 〈00l〉 oriented and rotated 45° with respect to the MgO substrate to minimize the misfit; the remaining strain was accommodated by dislocations, evident in transmission electron microscopy images. From high-resolution x-ray diffraction (XRD) measurements, the out-of-plane lattice parameter was determined to be 3.175 A, and the in-plane parameter was 3.153 A, i.e., the W film sustained a strain resulting in a tetragonal distortion of the lattice. XRD pole figures showed that the Al had four fold symmetry and two dominant orientations, 〈016〉 and 〈3 9 11〉, which were twinned with multiple placements on the epitaxial W layer. The driving force for the tilted 〈001〉 and 〈011〉 orientations of Al on W is due to strain minimization through ...

Low-temperature deposition of TiN by reactive evaporation or sputter deposition onto amorphous substrates leads to highly underdense layers which develop mixed 111/002 orientations through competitive growth. In contrast, we demonstrate here the growth of low-temperature (450 °C) fully dense polycrystalline TiN layers with complete 111 texture. This was achieved by reactive magnetron sputter deposition using a combination of: (1) highly oriented 25-nm-thick 0002 Ti underlayers to provide 111 TiN orientation through texture inheritance (local epitaxy) and (2) high flux (JN2+/JTi=14), low-energy (EN2+≃20 eV), N2+ ion irradiation in a magnetically unbalanced mode to provide enhanced adatom diffusion leading to densification during TiN deposition. The Ti underlayers were also grown in a magnetically unbalanced mode, in this case with an incident Ar+/Ti flux ratio of 2 and EAr+≃11 eV. All TiN films were slightly overstoichiometric with a N/Ti ratio of 1.02±0.03. In order to assess the diffusion-barrier propert...

ScN layers, 345 nm thick, were grown on MgO(001) substrates at 750 °C by ultrahigh-vacuum reactive magnetron sputter deposition in pure N2 discharges at 5 mTorr. The N2+ to Sc ratio incident at the substrate and growing film was maintained constant at 14, while the ion energy EN2+ was varied from 13 to 50 eV. All films were stoichiometric with N/Sc ratios of 1.00±0.02. However, microstructural and surface morphological evolution were found to depend strongly on EN2+. The nucleation and initial growth stages of ScN films deposited with EN2+=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 ≃50 nm as 002 grains grow out of existence in a kinetically limited competitive growth mode. In distinct contrast, films deposited with EN2+=20 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 EN2+ to ...

Tensile-strained Si0.6Ge0.4 alloys are deposited on Ge(001) by molecular beam epitaxy. The morphology and microstructure of as-deposited (6.5–130 nm thick deposited at 325–500 °C) and annealed (2 min at 625 or 700 °C) epitaxial films are studied by in situ scanning tunneling microscopy, ex situ atomic force microscopy, and transmission electron microscopy. 6.5 nm thick films deposited at 325 and 410 °C are atomically flat with low densities of partial dislocations; stress relaxation of 6.5 nm thick films is limited by dislocation blocking. The surface morphology of thicker films grown at 410 °C is strongly influenced by the interactions of stacking faults and surface steps. Annealing of 13 nm thick films at 700 °C produces a severe roughening with the formation of a regular pattern of 50 nm deep surface pits bounded by {113} facets.

Polycrystalline bcc TixW1−x layers with mixed 011 and 002 texture were grown on oxidized Si(001) substrates at 600 °C by ultrahigh-vacuum (UHV) magnetron sputter deposition from W and Ti0.33W0.67 targets using both pure Ar and Xe discharges. Ti concentrations in the 100-nm-thick layers were 0, 6, and 33 at. % depending on target composition and sputtering gas. Al overlayers, 190 nm, thick with strong 111 preferred orientation, were then deposited in Ar at 100 °C with and without breaking vacuum. Changes in bilayer sheet resistance Rs were monitored as a function of time ta and temperature Ta during subsequent UHV annealing. Thermal ramping of Al/W and Al/Ti0.06W0.94 bilayers at 3 °C min−1 resulted in large (>fourfold) increases in Rs at Ta≃550 °C, whereas Rs in the Al/Ti0.33W0.67 bilayers did not exhibit a similar increase until ≃610 °C. Area-averaged and local interfacial reactions and microstructural changes were also followed as a function of annealing conditions. The combined results indicate that Al/...

Polycrystalline bcc W layers, 110 nm thick with 011 preferred orientation and an average grain size of 40 nm, were grown on amorphous-SiO2/Si(001) substrates by ultrahigh vacuum (UHV) magnetron sputter deposition at Ts=600 °C. Al overlayers, 170 nm thick with strong 111 preferred orientation and an average grain size of 120 nm, were then deposited at Ts=100 °C without breaking vacuum. Changes in bilayer sheet resistance Rs were monitored continuously as a function of time ta and temperature Ta during UHV annealing. In addition, area-averaged and local interfacial reaction paths, as well as microstructural changes as a function of annealing conditions, were determined by x-ray diffraction, Rutherford backscattering spectroscopy, transmission electron microscopy (TEM), and scanning TEM in which compositional distributions in cross-sectional specimens were obtained by energy-dispersive x-ray analysis using a 1 nm diam probe beam. The two tungsten aluminides which form, WAl4 and WAl12, are nucleated essential...

A low‐energy, high‐brightness, broad beam Cu ion source is used to study the effects of self‐ion energy Ei on the deposition of epitaxial Cu films in ultrahigh vacuum. Atomically flat Ge(001) and Si(001) substrates are verified by in situ scanning tunneling microscopy (STM) prior to deposition of 300 nm Cu films with Ei ranging from 20 to 100 eV. Film microstructure, texture, and morphology are characterized using x‐ray diffraction ω‐rocking curves, pole figure analyses, and STM. Primary ion deposition produces significant improvements in both the surface morphology and mosaic spread of the films: At Ei>37 eV the surface roughness decreases by nearly a factor of 2 relative to evaporated Cu films, and at Ei≂35 eV the mosaic spread of Cu films grown on Si substrates is only ≂2°, nearly a factor of 2 smaller than that of evaporated Cu. During deposition with Ei≂25 eV on Ge substrates, the film coherently relaxes the 10% misfit strain by formation of a tilt boundary which is fourfold symmetric toward 〈111〉. T...

We demonstrate the use of 10 and 30 keV focused beams of Ga+ ions to thin, slice, weld, and alter the structure and composition of multiwalled carbon nanotubes at precise locations along the nanotube axis. This strategy of harnessing ion-beam-induced defect generation and doping could be attractive for modulating chemical and electrical properties along the nanotube length, and fabricate nanotube heterostructures and networks for device applications.

We use a combination of alloying and low-energy ion irradiation during film growth to controllably manipulate the nanostructure of TiN-based layers. Ti0.8Ce0.2N films are grown on SiO2 at 350 °C using UHV reactive magnetron sputtering in N2. The N2+-to-metal ratio incident at the growing film is maintained constant at 15, while the ion energy EN2+ is varied from 14 to 45 eV. Films grown with EN2+=14 eV consist of equiaxed nanograins with an average size of 2.0 nm, while layers deposited with EN2+=45 eV exhibit a 2-nm-wide nanocolumnar structure. In both cases, the films are dense, atomically smooth, and have strong 002 texture with low stress. This is in dramatic contrast to TiN films deposited under the same conditions, which are underdense with extremely rough surfaces and consist of broad (≃ 30 nm) columns. We attribute the formation of controlled nanostructures to the interplay between ion-irradiation-induced effects and thermally driven Ce surface segregation, leading to continuous renucleation during film growth.

The effects of the incident ion/metal flux ratio (1≤Ji /JTi≤15), with the N+2 ion energy Ei constant at ≂20 eV (≂10 eV per incident accelerated N), on the microstructure, texture, and stoichiometry of polycrystalline TiN films grown by ultrahigh‐vacuum reactive‐magnetron sputtering have been investigated. The layers were deposited in pure N2 discharges on thermally oxidized Si(001) substrates at 350 °C. All films were slightly overstoichiometric with a N/Ti ratio of 1.02±0.03 and a lattice constant of 0.4240±0.0005 nm, equal to that of unstrained bulk TiN. Films deposited with Ji/JTi=1 initially exhibit a mixed texture—predominately (111), (002), and (022)—with competitive columnar growth which slowly evolves into a pure (111) texture containing a network of both inter‐ and intracolumn porosity with an average column size of ≂50 nm at t=1.6 μm. In contrast, films grown with Ji/JTi≥5 do not exhibit competitive growth. While still columnar, the layers are dense with an essentially complete (002) preferred o...

Single‐crystal bcc W(001) layers, 140 nm thick, were grown on MgO(001) substrates by ultrahigh‐vacuum (UHV) magnetron sputter deposition at Ts=600 °C. Al overlayers, 190 nm thick with strong (001) and (011) preferred orientation and an average grain size of 200 nm, were then deposited at Ts=100 °C without breaking vacuum. Changes in bilayer sheet resistance Rs were monitored continuously as a function of time ta and temperature Ta during UHV annealing. In addition, Rutherford backscattering spectroscopy, x‐ray diffraction, transmission electron microscopy (TEM), and scanning TEM, in which cross‐sectional specimens were analyzed by energy‐dispersive x‐ray analysis with a 1 nm resolution, were used to follow area‐averaged and local interfacial reaction paths as well as microstructural changes as a function of annealing conditions. The initial reaction products were discontinuous regions of monoclinic‐structure WAl4 which exhibit a crystallographic relationship with the underlying W layer. bcc WAl12 forms at...

In this letter, we report an electron diffraction determination of chiral vectors (n,m) of individual single-wall carbon nanotubes (SWNTs). Electron diffraction patterns from individual SWNTs were recorded on imaging plates using a parallel electron beam over a section of tube of ∼50 nm long. Using two tubes of 1.39 and 3.77 nm in diameter, we show that the details of electron diffuse scattering can be detected for both the small and large tubes. The quality of diffraction patterns allows the accurate measurement of both the diameters and chiral angles of SWNTs for a direct determination of chiral vectors. The electron diffraction technique is general and applicable to other forms of individual nanostructures.

The effects of incident ion/metal flux ratio Ji/JMe and ion energy Ei on the microstructure, texture, and phase composition of polycrystalline metastable Ti0.5Al0.5N films produced by reactive magnetron sputtering have been investigated using x‐ray diffraction (XRD), plan‐view and cross‐sectional transmission electron microscopy, and Rutherford backscattering spectroscopy. The films, typically ≂1 μm thick, were deposited at a pressure of 20 mTorr (2.67 Pa) in pure N2 on thermally oxidized Si(001) substrates at 250±25 °C. The N2+ ion flux to the substrate was controlled by means of a variable axial magnetic field superimposed on the permanent magnetic field of the magnetron. Films deposited at Ei=20 eV (≂10 eV per incident accelerated N) with Ji/JMe=1 exhibited a complete (111) texture with a porous columnar microstructure and an average column size of ≂30 nm. Increasing Ei from 20 to 85 eV, while maintaining Ji/JMe constant at 1, resulted in a small change in texture as the XRD intensity ratio I002/(I111+...

We investigate the evolution of texture and grain morphology in fine-grained TiN thin films using cross correlation of dark-field images obtained using annular objective apertures with radii that correspond to different low index TiN reflections. This technique enables parallel analyses of the orientations of thousands of grains, with a spatial resolution of order 10 nm. Preferred grain orientations were determined for 40 and 100 nm thick TiN layers grown on SiO2 by magnetically unbalanced reactive magnetron sputter deposition. We find that no single orientation is dominant in the 40 nm films but that a 〈100〉 texture has developed by the time these films reach 100 nm in thickness.

Ti0.5Al0.5N alloy films, typically 1.5 μm thick, were grown on MgO(001) at temperatures Ts between 400 and 850 °C by ultra‐high‐vacuum reactive magnetron sputtering in pure N2. Films grown at Ts between ≂480 and 560 °C were single crystals in which the lattice misfit strain was partially relieved by glide of 〈001〉 misfit dislocations, with Burgers vector =a0/2〈011〉, on {011} planes. Cross‐sectional transmission electron microscopy investigation showed no evidence of residual extended defects in the films until thicknesses of ≂150 nm at which point threading dislocations, oriented along the [001] growth direction, were observed. Surface‐initiated spinodal decomposition, resulting in the formation of compositionally modulated NaCl‐structure platelets along [001] with width ≂1 nm, occurred over a narrow growth temperature range between 540 and 560 °C as a precursor to bulk phase separation of wurtzite‐structure AlN at Ts≥560 °C. The alloy was continuously depleted of AlN at higher growth temperatures until ...

The evolution of surface morphology and microstructure during growth of single crystal TiN(001) is characterized by in situ scanning tunneling microscopy and postdeposition plan-view transmission electron microscopy. The TiN layers are grown on MgO at 650

Sputter‐deposited Ti1−xWx diffusion barriers in microelectronic devices have been reported by many groups to be Ti deficient with respect to the target composition. In the present experiments, polycrystalline TixW1−x alloys were grown on oxidized Si(001) substrates at temperatures Ts between 100 and 600 °C by ultrahigh‐vacuum magnetron cosputter deposition from pure W and Ti targets in 5 mTorr (0.65 Pa) Ar and Xe discharges. Films deposited in Ar were found by Rutherford backscattering and Auger electron spectroscopies to be increasingly Ti deficient with increases in the Ti sputtering rate and/or Ts at a constant W sputtering rate. TRIM calculations and Monte Carlo gas‐transport simulations were used, in combination with the experimental results, to show that the Ti loss was due primarily to differential resputtering of the growing film by energetic Ar particles backscattered from the heavier W target. This effect is exacerbated at elevated film growth temperatures by Ti surface segregation in the alloy....

The preferred orientation of polycrystalline TiN films grown by ultrahigh‐vacuum reactive‐magnetron sputter deposition on amorphous SiO2 at 350 °C in pure N2 discharges was controllably varied from (111) to completely (002) by varying the incident ion/metal flux ratio Ji/JTi from 1 to ≥5 with the N+2 ion energy Ei maintained constant at ≂20 eV (≂10 eV per incident accelerated N). All samples were slightly over‐stoichiometric with N/Ti=1.02±0.03. Films deposited with Ji/JTi=1 initially exhibit a mixed texture with competitive columnar growth which slowly evolves into a nearly complete (111) texture at film thicknesses greater than 1 μm. However, films grown with Ji/JTi≥5 exhibit an essentially complete (002) preferred orientation from the earliest observable stages. The normalized XRD (002) intensity ratio in thick layers increased from ≂0 to 1 as Ji/JTi was varied from 1 to ≥5. Both (111) and (001) interplanar spacings remained constant as a function of film thickness yielding a lattice constant of 0.4240...

Epitaxial metastable zinc‐blende‐structure β‐AlN was synthesized by the solid‐state reaction between single‐crystal Al(001) and TiN(001) layers grown on MgO(001) by ultrahigh vacuum magnetron sputter deposition. At an annealing temperature Ta=600 °C, the interaction proceeded according to the following overall reaction: 4Al+TiN→Al3Ti+AlN, in which β‐AlN was formed pseudomorphically between cubic TiN and tetragonal Al3Ti layers. The lattice constant of β‐AlN was found to be 0.438 nm, which corresponds to a 3.3% lattice mismatch with the underlying TiN layer.

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

Using in situ high-temperature (700-1000 K) scanning tunneling microscopy (STM), we studied the influence of ethylene on the surface dynamics of oxygen-deficient, rutile-structured TiO2(110). STM images were acquired during annealing the sample as a function of time, oxygen and ethylene pressures, and temperature. With increasing oxygen pressure and/or decreasing temperature, TiO2(110) surface mass increased, consistent with previous results. Interestingly, annealing the sample in ethylene with traces of oxygen also results in the growth of TiO2 at higher rates than those observed during annealing in pure oxygen. Our results indicate that ethylene promotes oxidation of TiO2(110).

For optoelectronic applications requiring unconventional substrates, use of flexible forms of semiconductors may be inevitable. We have fabricated a flexible form of single crystalline AlN ribbons with periodic and wavelike structures on an elastomeric substrate. Single crystalline AlN films were grown on Si (111) substrate using high vacuum unbalanced magnetron sputtering. Crystallinity of the AlN films was confirmed with x-ray diffraction and pole figure. The AlN ribbons were transferred to a prestrained (3.1%) elastomeric substrate and the resulting “wavy” ribbons on the substrate were flexible up to 30% strain without any crack formation on the surface. As the film thickness changed from 300 to 900 nm, the periods of the waves varied from 95 to 277 μm, which were within a 10% error of the calculated values. When we applied more than 30% strain, mechanical instability, such as the failure of AlN ribbons due to the cracks on the surface and the merged ribbons, was observed.

Group-IV HfNx transition-metal nitride layers, with 0.85≤x≤1.50, are grown on MgO(001) and analyzed by Raman spectroscopy. Samples with 0.85≤x≤1.20 are single-phase epitaxial NaCl-structure HfNx(001), while layers with higher N concentrations are two-phase mixtures containing N-rich inclusions. All samples exhibit both first- and second-order Raman scattering. The presence of first-order scattering indicates that Oh symmetry, a characteristic of the NaCl crystal structure, is broken even in stoichiometric HfN. As x decreases in understoichiometric HfNx samples, corresponding to a decrease in the number of valence electrons per unit cell from nine (x=1) to eight (x=0.75), the positions of the acoustic lines shift to higher frequencies. This provides an indirect probe of phonon anomalies in acoustic mode dispersion curves and signifies an increase in N vacancy concentration. The persistence of strong first-order acoustic scattering from overstoichiometric (x>1) samples indicates that adding more N does not substantially reduce the average defect density around Hf sites. The absence of a frequency shift in the acoustic modes of overstoichiometric HfNx, with 1.17≤x≤1.27, also shows that the local order around Hf sites does not change significantly, while the observed shift of the first-order optical modes to higher frequency with increasing x is characteristic of increasing lattice disorder adjacent to N sites. The Raman results, together with the nature of the variation in the HfNx lattice parameter, the electron carrier concentration, and the superconducting transition temperature as a function of x, can be explained by the presence of N vacancies for x 1.

The effects of P doping on growth kinetics and surface morphological evolution during Si(001):P gas-source molecular beam epitaxy from Si2H6 and PH3 at temperatures Ts=500–900°C have been investigated. With increasing PH3∕Si2H6 flux ratio JP∕Si at constant Ts, we observe a decrease in the film growth rate R and an increase in the incorporated P concentration CP, both of which tend toward saturation at high flux ratios, which is accompanied by increased surface roughening and pit formation. At constant JP∕Si, R increases with increasing Ts, while CP initially increases, reaches a maximum at Ts=700°C, and then decreases at higher growth temperatures. We use in situ isotopically tagged D2 temperature programed desorption (TPD) to follow changes in film surface composition and dangling bond density θdb as a function of JP∕Si and Ts. Measurements are carried out on both as-deposited Si(001):P layers and P-adsorbed Si(001) surfaces revealing β1 and β2 peaks due to D2 desorption from Si monohydride and dihydride...

Single-crystal group-V δ-TaNx transition-metal (TM) nitride layers, with x ranging from 0.94 to 1.37, are grown on MgO(001) and analyzed by Raman spectroscopy. In perfect NaCl-structure crystals, the first-order Raman modes are not allowed by the Oh crystal symmetry. Since first-order acoustic and optical bands are observed for all δ-TaNx samples, this indicates the presence of point defects, even for stoichiometric TaN. The large mass difference between Ta and N leads to a correspondingly large separation between the first-order acoustic and optical bands centered at 150 and 550 cm−1, respectively. A Raman peak at 440 cm−1, overlapping the first-order optical band, is identified as the difference between the first-order optical and acoustic modes. Contrary to the case for most TM nitrides, there is no peak visible in the second-order high-frequency range (700–1500 cm−1). In addition, the first-order transverse (120 cm−1) and longitudinal acoustic peaks (175 cm−1) do not exhibit the frequency shift with N/Ta ratio x (i.e., with the valence electron density) that has been reported for group-IV TM nitrides. This is consistent with the resistivity of TaNx remaining essentially constant, as well as with the very weak dependence of the lattice parameter as a function of the N/Ta ratio, and suggests that the wide single-phase region in this system is due to the presence of isoelectronic antisite substitutions rather than, as has been proposed previously, cation and anion vacancies.

An excellent adhesion of hard coatings to steel substrates is paramount in practically all application areas. Conventional methods utilize Ar glow etching or cathodic arc discharge pretreatments that have the disadvantage of producing weak interfaces or adding droplets, respectively. One tool for interface engineering is high power impulse magnetron sputtering (HIPIMS). HIPIMS is based on conventional sputtering with extremely high peak power densities reaching 3kWcm−2 at current densities of >2Acm−2. HIPIMS of Cr and Nb was used to prepare interfaces on 304 stainless steel and M2 high speed steel (HSS). During the pretreatment, the substrates were biased to Ubias=−600V and Ubias=−1000V in the environment of a HIPIMS of Cr and Nb plasma. The bombarding flux density reached peak values of 300mAcm−2 and consisted of highly ionized metal plasma containing a high proportion of Cr1+ and Nb1+. Pretreatments were also carried out with Ar glow discharge and filtered cathodic arc as comparison. The adhesion was ev...

Nanocrystalline films with high hardness have attracted increasing interest for wear resistant applications. Specifically, nanocrystalline Ti–B–N layers have been demonstrated to exhibit enhanced hardness and thermal stability. Here, we show that Ti–B–N films grown at 300°C and consisting of a high volume fraction, ∼50%, of a fully percolated disordered phase encapsulating 2–3nm wide TiN and TiB2 grains, have a hardness of 37GPa and an elastic modulus of 332GPa which increase with annealing to 43 and 362GPa, respectively, at Ta=800°C. The structural rearrangement which occurs during annealing results in the formation of compact interface boundaries which lead, in turn, to the observed hardness increase. Annealing at Ta>900°C decreases the hardness, although the elastic modulus continues to increase, due to the combination of grain growth and B loss via the formation of volatile boron oxides and hydroxides. These conclusions, obtained based upon a combination of x-ray diffraction, nanoindentation, electron...

CoSi2 layers

Stoichiometric single-crystal HfN layers grown on MgO(001) are analyzed by Raman spectroscopy. Second-order Raman scattering predominates, but first-order modes in the acoustic and optical ranges are also visible. The latter indicates that the Oh symmetry of NaCl-structure HfN is broken. The large mass difference between Hf and N leads to a correspondingly large separation, 250cm−1, between the first-order acoustic and optical bands. Within this gap, four Raman lines are clearly observed. The first three are the second-order transverse acoustic mode (240cm−1), the sum of the first-order transverse and longitudinal acoustic modes (280cm−1), and the second-order longitudinal acoustic mode (325cm−1). The fourth line at 380cm−1 is identified as the difference between the first-order optical and acoustic modes. The observed first-order Raman scattering, as well as the width of the gap between the first-order acoustic and optical modes, is in good agreement with previously calculated HfN phonon density of states.

Field-effect transistors with carbon nanotubes (CNTs) suspended across etched slits and fabricated by chemical vapor deposition have been characterized by electrical measurements and transmission electron microscopy. Two devices are examined here: One is semiconducting from two single-wall CNTs, and the other is semiconducting and metallic, with a large off current, that comes from multiple nanotubes. The study highlights the importance of structural characterization in understanding the performance of CNT devices.

We use in situ low-energy electron microscopy to investigate the near-equilibrium dynamics of TiN(111) steps, pinned by surface-terminated dislocations, as a function of N2 pressure pN2 and time during annealing of TiN(111) layers at temperatures T between 1600 and 1735 K. At each T, we observe the nucleation and growth of spiral steps rotating around dislocation cores. The spirals undergo a shape-preserving motion with a constant angular velocity ω as they grow inward, normal to the surface, forming vacancy pits. We find that ω for successive spirals emanating from the same source decreases slowly with time at all pN2 values between vacuum and 5×10−7Torr. From the ω(T) data, we obtain an activation energy of 4.6±0.2eV, irrespective of pN2, for the growth of spiral steps.

TiB2 thin films are well known for their high hardness which makes them useful for wear-resistant applications. Overstoichiometric TiB2 deposited at 300 °C by nonreactive sputtering has been shown to exhibit superhardness (H⩾40GPa), while the hardness of their bulk stoichiometric counterparts is ∼25GPa. We show, using high-resolution transmission electron microscopy, that overstoichiometric TiB2.4 layers have a complex self-organized columnar nanostructure. The ∼20nm wide columns, encapsulated in excess B and oriented along 0001, consist of a bundle of ∼5nm diameter TiB2 subcolumns separated by an ultrathin B-rich tissue phase. The nanocolumnar structure, which is thermally stable to postannealing temperatures up to 700 °C, inhibits nucleation and glide of dislocations during hardness indentation measurements, while the high cohesive strength of the B-rich tissue phase prevents grain-boundary sliding. The combination of these effects results in the observed superhardness of ∼60GPa.

CaF2-structure CoSi2 layers were formed on Si(001) by reactive deposition epitaxy (RDE) and compared with CoSi2 layers obtained by conventional solid phase growth (SPG). In both sets of experiments, Co was deposited by ultrahigh-vacuum magnetron sputtering and CoSi2 formed at 600°C. However, in the case of RDE, CoSi2 formation occurred during Co deposition while for SPG, Co was deposited at 25°C and silicidation took place during subsequent annealing. X-ray diffraction pole figures and transmission electron microscopy results demonstrate that RDE CoSi2 layers are epitaxial with a cube-on-cube relationship, (001)CoSi2‖(001)Si and [100]CoSi2‖[100]Si. In contrast, SPG films are polycrystalline with an average grain size of ≃1000A and a mixed 111∕002∕022∕112 orientation. We attribute the striking difference to rapid Co diffusion into the Si(001) substrate during RDE for which the high Co∕Si reactivity gives rise to a flux-limited reaction resulting in the direct formation of the disilicide phase. In contrast,...

During bombardment of a stainless steel sample by 5 keV D+ ions we study simultaneously the reemission of D2 molecules and the depth distribution of deuterium in the target. We determine separately the depth distribution of trapped and mobile deuterium. The mobile component exhibits a uniform density to a depth of 850 A. A determination is made of the surface recombination rate coefficient relating the emission of free molecules to the density of mobile atoms in the surface. A value of 1.5×10−29 cm4 s−1 is determined for a target at 30 °C. Data are presented up to a 100 °C target temperature and are consistent with previous determinations at higher temperatures. A simple model shows how reemission varies with bombardment fluence and permits a separate evaluation of the recombination rate from the temporal dependence of reemission.

A method of analysis has been developed by which the atomic composition of binary compound thin films can be determined, using Rutherford backscattering techniques. The advantage of the approach discussed in this paper is that the atomic concentration of the lighter material in the film can be deduced without taking into account the backscattering signals from the lighter element. This is of special importance whenever signals from the lighter element suffer from large statistical errors, or are not observable at all in a backscattering spectrum. A few examples of calculations, done with a developed computer program, as well as some experimental results are presented and discussed. It is shown that the atomic concentration of the lighter element in a compound film generally can be determined with an accuracy of about 5%.