Effect Of Nitrogen Partial Pressure Research Articles

Optimization of the superconducting properties of NbTiN thin films by variation of the N2 partial pressure during sputter deposition

We report the effect of nitrogen partial pressure on the growth of niobium-titanium nitride (NbTiN) thin films through reactive sputtering of the NbTi target in the presence of Ar and N2 atmosphere. The N2 partial pressure was varied from 5.8% to 15.15% with respect to the Ar flow available in the chamber. We measured a critical temperature (T C) as high as 15.77 K for an N2 partial pressure of 6.8% for a 50 nm film deposited on an MgO substrate. The epitaxial growth of the NbTiN films is evident from the observed (200) and (400) XRD peaks with respect to the substrate. The superconducting properties were analyzed with respect to the observed values of T C, ΔT C, temperature dependence of the upper critical field (B C2), coherence length (ξ), diffusion coefficient (D), and the thermally activated flux flow behavior following the Arrhenius equation. The T C variation observed for the entire spectrum of N2 partial pressure variation is ∼11%, with T C getting saturated towards the higher end of the N2 content. While the T C variation with respect to N2 content is non-linear, the variation of B C2(0), diffusion coefficient, and zero temperature coherence length ξ(0) show a linear dependence. While the B C2(0) values show an increasing trend, D and ξ(0) values show a decreasing trend with respect to the increase of N2 partial pressure. It is concluded that the optimum window of N2 partial pressure for the reactive sputtering of NbTiN using a target of Nb0.7Ti0.3 for the present experimental conditions, in terms of epitaxial growth and obtaining the highest T C is within the range of 5.8% to 8.51%.

Effect of Nitrogen Partial Pressure on Structure, Mechanical Property, and Corrosion Behavior of ZrNx Films Prepared by Reactive DC Magnetron Sputtering.

ZrNx films were deposited by DC magnetron sputtering with pure Zr target in different nitrogen partial pressure atmospheres (r = N2/[Ar + N2]). The structure and composition of the thin films were characterized as a function of r using scanning electron microscope, glancing angle X-ray diffraction, and X-ray photoelectron spectroscopy. The hardness, adhesive strength, and corrosion behavior of the coatings were measured by nanoindentation, microscratch, and potentiodynamic measurements in 3.5 wt% NaCl solution. The results show that the structure of the ZrNx films changes from a nearly stoichiometric ZrN with a typical columnar structure to mixed phases composited of ZrN and α-ZrNx with a dense glass structure as r increases from 12% to 50%. The mechanical properties including hardness, elastic modulus, and adhesion decrease with increasing r due to nonstoichiometric compound and glass phase structure of the coatings, while the dense glass structure significantly improves the corrosion inhibition.

Effect of nitrogen partial pressure on the piezoresistivity of magnetron sputtered ITO thin films at high temperatures

Various ITO thin films were deposited by RF magnetron sputtering with different nitrogen partial pressure (NPP) of 10 %∼40 % to quantitatively modify their high temperatures piezoresistivity. The valence band structures and element states of the ITOthin filmswere examined by X-ray photoelectron spectroscopy. Results show that the Fermi energy level (EF) shifts closer to the maximum energy of valence band with the growth ofthe NPP, which will cause a reduction of the number of electrons ionized to the conduction band. The 20 %N2ITOthin film shows the smallest content change rates of nitrogen (3.8 %) and oxygen (1.6 %) after the piezoresistivity test at 600 °C, 800 °C and 1000 °C. The lowest resistance drift rate was also observed in the 20 %N2ITOthin film in the above test due to its chemical stability of the incorporated nitrogen. Moreover, the gauge factor (GF) declines from 2.28 to 1.48 with the increase of the NPP at 600 °C due to the decline of the amounts of electrons ionized to the conduction band since the shift of the EF. The 20 %N2ITOthin film strain gauge has the highest GF at 800 °C and 1000 °C owing to its smallest content change rates.

Effect of Nitrogen Partial Pressure on the Structural, Mechanical, and Electrical Properties of (CrHfNbTaTiVZr)N Coatings Deposited by Reactive Magnetron Sputtering

Multi-element (CrHfNbTaTiVZr)N coatings were prepared through the magnetron sputtering of an equimolar CrHfNbTaTiVZr alloy target. This study determined the influences of N2-to-total (N2 + Ar) ratios (RN) on the composition, structure, mechanical properties, and electrical performance of the coatings. Coating thickness decreased from 898 nm to 128 nm with increasing RN from 0% to 100%. The alloy coating has bundles of fibrous structures with remarkable void boundaries. The coating changed from amorphous phase to face-centered cubic (FCC) phase with (111) preferred orientation, then to FCC phase with (200) preferred orientation, and finally to near-amorphous phase as RN increased from 0% to 100%. The microstructure of the nitride coatings transformed from a columnar structure with rough faceted tops and void boundaries into a dense and small structure with smooth domed tops. The grain size of the nitride coatings also decreased with RN. Accordingly, the electrical performance at high RN was poor. The nitride coating deposited at RN = 60% had the highest hardness of 16.6 GPa and the lowest friction coefficient of 0.52, owing to structural densification and grain refinement.

Effect of nitrogen partial pressure on the TCR of magnetron sputtered indium tin oxide thin films at high temperatures

Indium tin oxide (ITO) is a promising sensitive material for ultra-high temperature thin-film sensors (UTTSs) applied in thermal and mechanical parameters test in hot section parts. However, the instability of the temperature coefficient of resistance (TCR) in the ITO film is still one of the major limiting factors in accuracy improvement of the UTTSs. In this work, different ITO thin film samples were prepared by RF magnetron sputtering with various N2/Ar ratios changing from 10%–40%, and the effect of nitrogen partial pressure (NPP) on the TCR of ITO films in elevated temperature from 500 °C to 1200 °C was studied. The micromorphology, crystallographic structures and electrical performances of ITO films were examined by scanning electron microscope (SEM), X-ray diffraction (XRD) and Hall effect measurement, respectively. Results show that lower crystallinity and smaller grain of ITO films can be observed with the increase of NPP. In addition, we found that the recrystallization is one of the main factors affecting the TCR repeatability in the thermal cycle test. The grain growth rate (GGR) is only 27.0% in the 20%N2 ITO film after the thermal cycle test from 500 °C to 1200 °C, far lower than that of the 40%N2 ITO film (309.6%). Consequently, the 20%N2 ITO film showed the lowest TCR volatility rates (TVR) after the thermal cycle test, which were respectively recorded as only about 0.5% and 2.1% at 800 °C and 1200 °C. The high TCR stability in the 20%N2 ITO film can be attributed to the formation of the stable phase structure during the thermal cycle test. Furthermore, the 20%N2 ITO film also has the smallest TCR compared with other ITO films.

Effect of nitrogen partial pressure on microstructure and mechanical properties of Mo-Cu-V-N composite coatings deposited by HIPIMS

The Mo-Cu-V-N composite coatings were deposited by high power impulse magnetron sputtering (HIPIMS) using a single Mo-Cu-V spliced target in an Ar–N2 atmosphere. The effect of nitrogen partial pressure on the microstructure, mechanical properties and tribological behavior of the coatings was investigated. The results indicated that the Mo-Cu-V-N composite coatings exhibited (111), (200) and (220) diffraction peaks of fcc B1-MoN phase, and then the phase structure changed to hex δ-MoN phase when the N2 partial pressure was higher than 0.35Pa. All the coatings showed a relatively smooth surface and columnar-type microstructure. As the N2 partial pressure increased from 0.11Pa to 0.35Pa, the hardness showed a slight decrease from 20.6GPa to 16.4GPa, which would be due to the relaxation of residual stress, and then rebounded to 17.1GPa with the formation of mixed phases of B1-MoN and δ-MoN. All of the Mo-Cu-V-N composite coatings exhibited a relatively low friction coefficient of approximately 0.3 and the wear rate was in the small range of 8.9×10−17m3/N·m to 17.3×10−17m3/N·m. The formation of mixed lubricious oxides of MoO3 and V2O5 was expected to account for the excellent tribological properties.

The effects of nitrogen partial pressure on the microstructure of amorphous carbon nitride films

ABSTRACTThe amorphous carbon nitride (a-CNx) films with varying nitrogen content were deposited on Si (100) wafers substrates using radio frequency magnetron sputtering (RFMS) from graphite target at different nitrogen partial pressure. The influence of nitrogen partial pressure on the microstructure and phase composition of a-CNx films were researched systematically. The films were characterized by atom force spectroscopy (AFM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). AFM results showed cluster structure in a range of tens to hundreds namometers existed on the surface of the films and the surface roughness increased with the increase of nitrogen partial pressure. Ratio of ID/IG increased with the nitrogen partial pressure, while the sp3 phase content from fitting results of XPS displayed reverse trend. The nanohardness of a-CNx films characterized by nanoindentation test decreased with the increase of nitrogen partial pressure, which consisted with the results of Raman and XPS. Thus high nitrogen partial pressure caused the mechanical properties of a-CNx films decrease.

Microstructure evolution and its effect on thermo-mechanical properties of low-carbon Al2O3-C refractories

Low-carbon Al2O3-C refractory samples were prepared from raw materials of tabular alumina, reactive alumina powder, flake graphite and carbon black. Silicon powder and metallic Al powder were used as additives and phenol resin was used as binder. The effects of nitrogen partial pressure and firing temperature on microstructural evolution and the thermo-mechanical properties of low-carbon Al2O3-C refractories were investigated. The thermodynamic calculations for Al–Si–O–C–N systems suggested that SiC, AlN and β-Sialon could be stable under different nitrogen partial pressures. The experimental results showed that short columnar AlN and SiC whiskers were formed at 1200°C. The aspect ratio of AlN was higher and SiC production become larger with nitrogen partial pressure increasing. Two-dimensional flaky β-Sialon could be generated as the nitrogen partial pressure increased to higher than 0.11MPa at 1400°C. Due to the formation of SiC whiskers and β-Sialon, the cold modulus of rupture and the cold crushing strength were improved from 12.8MPa to 19.3MPa and from 57.3MPa to 74.7MPa, respectively. The load displacement could be increased by 62% to 0.59mm. At the same time, the maximum values of flexural modulus and hot modulus of rupture reached 4.2GPa and 13.2MPa, respectively. After three thermal shock cycles, the CCS of refractories containing the SiC whiskers and β-Sialon only decreased by 6.2MPa. The in situ formation of SiC whiskers and β-Sialon could greatly enhance the thermo-mechanical properties of low-carbon Al2O3-C refractories.

Effect of nitrogen flow rate on structural and mechanical properties of Zirconium Tungsten Nitride (Zr–W–N) coatings deposited by magnetron sputtering

The effect of nitrogen partial pressure (pN2) on structural, composition, deposition rate and mechanical properties of Zirconium Tungsten Nitride (ZrxW1−xNy) thin films have been studied. ZrxW1−xNy thin films have been deposited on silicon (100) substrates by DC/RF reactive magnetron sputtering. Structure and elemental composition of the deposited ZrxW1−xNy thin films strongly depend on pN2. XRD analysis shows that for 0.07Pa≤pN2≤0.17Pa, ZrxW1−xNy films exhibit single (fcc) phase, for 0.20Pa≤pN2≤0.27Pa, an amorphous phase is obtained and for 0.33Pa≤pN2≤0.67Pa reflections corresponding to dual (fcc+hcp) phase have been observed. The phase formation has been confirmed by TEM diffraction patterns. The root mean square roughness of the films varies non-monotonically with increasing pN2. The thickness of the films decreases continuously with increasing pN2. Results of nano-indentation analysis confirm moderate hardness, high wear resistance, high resistance to fatigue fracture and high adhesiveness of ZrxW1−xNy films. Among all the phases, maximum hardness (~24GPa) and maximum reduced elastic modulus (135GPa) have been obtained for dual phase (fcc+hcp) film while resistance to fatigue fracture (H3/Er2~0.87GPa), wear resistance (H/Er~0.2) and ductility for single phase (fcc) film were found to be maximum. No crack was observed to propagate in the films at a high load of 50mN. All the films were found to exhibit high adhesion with the substrate surface.

Effects of nitrogen partial pressure in Ta–N films grown by the cathodic vacuum arc technique

Ta–N films were prepared by the cathodic vacuum arc technique in Ar + N2 atmosphere with various nitrogen partial pressures . The crystal structure, chemical composition, surface morphology and cross-section morphology of the Ta–N films were investigated by x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy and atomic force microscopy. The influence of nitrogen partial pressure on the material characteristics of the Ta–N film was systematically studied. Our results suggest that the structural and morphological properties of the Ta–N films have a strong dependence on the nitrogen partial pressure. With increasing nitrogen partial pressure from 0% to 100%, the phase composition of the films evolves from single tetragonal Ta to cubic TaN and then to multi-phase cubic TaN + monoclinic Ta3N5. And the crystallographic orientation of the main phase component, cubic TaN, develops from (1 1 1) preferred orientation to (2 0 0) preferred orientation. The N/Ta ratio of the films does not increase linearly with nitrogen partial pressure, and nearly reaches 1 : 1 at a nitrogen partial pressure of 65%. The deposition rate is found to decrease almost linearly with increasing nitrogen partial pressure. Macroparticles can be observed without using a magnetic filter, the amount of which can be significantly reduced by increasing the nitrogen partial pressure. And the smooth surface of the films is composed of nano-crystallites, while the grain size seems to increase as a function of the nitrogen partial pressure.

Structural, mechanical, electrical and wetting properties of ZrNx films deposited by Ar/N2 vacuum arc discharge: Effect of nitrogen partial pressure

Non-stiochiometric zirconium nitride (ZrNx) thin films have been deposited on silicon substrates by vacuum arc discharge of (N2+Ar) gas mixtures at different N2 partial pressure ratio. The microstructure, mechanical, electrical and wetting properties of these films are studied by means of X-ray diffraction (XRD), micro-Raman spectroscopy, Rutherford back scattering (RBS) technique, conventional micro-hardness testing, electrical resistivity, atomic force microscopy (AFM) and contact angle (CA) measurements. RBS results and analysis show that the (N/Zr) ratio in the film increases with increasing the N2 partial pressure. A ZrNx film with (Zr/N) ratio in the vicinity of stoichiometric ZrN is obtained at N2 partial pressure of 10%. XRD and Raman results indicate that all deposited films have strained cubic crystal phase of ZrN, regardless of the N2 partial pressure. On increasing the N2 partial pressure, the relative intensity of (111) orientation with respect to (200) orientation is seen to decrease. The effect of N2 partial pressure on micro-hardness and the resistivity of the deposited film is revealed and correlated to the alteration of grain size, crystallographic texture, stoichiometry and residual stress developed in the film. In particular, it is found that residual stress and nitrogen incorporation in the film play crucial role in the alteration of micro-hardness and resistivity respectively. In addition, CA and AFM results demonstrate that as N2 partial pressure increases, both the surface hydrophobicity and roughness of the deposited film increase, leading to a significant decrease in the film surface free energy (SFE).

Characterization of W[sbnd]Ta[sbnd]N hard films synthesized by direct current magnetron sputtering

WTaN hard films with Ta/(W+Ta)=46at.% were deposited on single crystal Si (111) substrates using direct current magnetron sputtering. The effect of nitrogen partial pressure (pN2) on crystal structure, surface topography, adhesion strength, and hardness of WTaN films was investigated. With increasing pN2, the phase composition changes from pure fcc W–Ta–N phase to a mixture of fcc WTaN phase and hexagonal δ-W(Ta)N phase, and then to pure hexagonal δ-W(Ta)N phase; the average grain size decreases monotonously; the surface becomes more and more smooth; the hardness initially increases and then decreases after passing a maximum of 41GPa at pN2=0.5Pa, while the adhesion strength varies in an opposite trend to the hardness. The maximum hardness could be due to the combined effect of reduced crystallite size and the coexistence of two phases.

Phase composition and tribological performance of molybdenum nitride coatings synthesized by IBAD

Molybdenum nitride coatings were synthesized by ion-beam-assisted-deposition (IBAD). The effects of nitrogen partial pressure and bombarding ion energy on the phase formation were investigated. The coefficient of friction and wear resistance of the coatings in different environments were studied.The stoichiometric ratio of nitrogen to Mo of the molybdenum nitride phases increases with the nitrogen partial pressure, and higher bombarding ion energy was helpful to form single MoN phase. Mo2N, MoN or mixture of the two phases could be prepared by controlling of the ratio of nitrogen/argon and ion energy. The hardness, coefficient of friction, wear and oxidation resistance of MoN were superior to that of Mo2N coating. The coefficient of friction decreased with the increase of testing temperature, yet the wear resistance became lower. The change of friction in non-oxidation atmosphere was reversed to that in the open air, indicating that the low friction of MoN at elevated temperature depends on oxidation. The tribological performance of the MoO3 phase formed by oxidation annealing showed much higher coefficient of friction than that of as-deposited MoN in all the testing conditions, and the oxygen deficient oxides were implied to be the lubricious phases.

The Effect of Nitrogen Partial Pressure and Substrate Temperature on the Characteristics of Photocatalytic N:TiO2 Thin Films deposited by Filtered Vacuum Arc Deposition

Nitrogen doped Titanium Oxide (N:TiO2) thin films were deposited using filtered vacuum arc deposition, and their structure, composition and morphology were studied as functions of the total pressure, N2/O2 gas ratio and the substrate temperature. The film structure, surface morphology, and composition were determined by XRD, AFM and XPS. The optical characterization of the films was determined with spectrophotomery and ex-situ variable angle spectroscopic ellipsometry (VASE). In addition to the effects of other deposition conditions such as arc current, total deposition pressure, and post-deposition annealing on the film characteristics, photocatalytic activity was also determined as a function of deposition parameters and results were discussed.

Effect of nitrogen partial pressure on Al–Ti–N films deposited by arc ion plating

AlTiN films with different nitrogen partial pressures were deposited using arc ion plating (AIP) technique. In this study, we systematically investigated the effect of the nitrogen partial pressure on composition, deposition efficiency, microstructure, macroparticles (MPs), hardness and adhesion strength of the AlTiN films. The results showed that with increasing the nitrogen partial pressure, the deposition rate exhibited a maximum at 1.2 Pa. Results of X-ray photoelectron spectroscopy (XPS) analysis revealed that AlTiN films were comprised of Ti–N and Al–N bonds. XRD results showed that the films exhibited a (1 1 1) preferred growth, and AlTi 3N and TiAl x phases were observed in the film deposited at 1.7 Pa. Analysis of MPs statistics showed MPs decreased with the increase in the nitrogen partial pressure. In addition, the film deposited at 1.2 Pa possessed the maximum hardness of 38 GPa and the better adhesion strength.

Comparative Study of Ta-N and W-N Films Deposited by Reactive Magnetron Sputtering

W-N and Ta-N films were fabricated using radio frequency reactive magnetron sputtering in a mixture, of Ar and N(2). The effect of nitrogen partial pressure (p(N2/)p(tot)) on the structure, morphology, and hardness of Ta-N and W-N films has been investigated comparatively. Dependent upon p(N2)/p(tot), the crystalline structure of W-N films changes from a single bcc alpha-W(N) phase to a mixture of alpha-W(N) and fcc beta-W(2)N phases at first, and then to a single fcc beta-W(2)N phase. In contrast, the crystalline structure of Ta-N changes initially from a single fcc-TaN phase to a mixture of fcc-TaN phase and orthorhombic Ta(3)N(5) phase, and then to a single orthorhombic Ta(3)N(5) phase. The hardness of W-N and Ta-N films increases gradually at first and then decreases slightly with increasing N(2) partial pressure after passing a maximum at the nitrogen partial pressure corresponding to the appearance of mixed phases.

Effect of nitrogen partial pressure on the structure, physical and mechanical properties of CrB 2 and Cr–B–N films

The investigation of structure and properties of Cr–B and Cr–B–N films deposited by direct current magnetron sputtering of CrB 2 target in argon and argon–nitrogen environments, respectively is presented. The nitrogen partial pressure was kept at 10, 15, and 25% of the total pressure. The microstructure, phase and chemical composition of Cr–B–(N) films were studied by means of X-ray diffraction, transmission- and scanning-electron microscopy, X-ray photoelectron spectroscopy, electron probe microanalysis and secondary neutral mass-spectrometry. The films were characterized in terms of their electrical resistivity, optical reflectivity and transmittance. Measurements of hardness and elastic modulus were performed by depth sensing nanoindentation. The results obtained show that the films deposited in pure Ar had a hexagonal AlB 2-type structure with crystallites, 15–17 nm in lateral size, elongated in the direction of film growth. The Cr–B–N films consisted of nanocrystalline nc-CrB 2 and amorphous a-BN phases. As the nitrogen content in films was raised, the volume fraction of the nc-CrB 2 phase decreased and a-BN phase increased. When nitrogen was added to the gas discharge during deposition, the nc-CrB 2 crystallite size decreased down to 3–5 nm. Without nitrogen, the films exhibited a columnar morphology. Nitrogen introduction suppressed the columnar growth of films because formation of a-BN intergranular layers. The films deposited under optimal parameters showed hardness in the range of 36–43 GPa and Young's modulus below 300 GPa. For all films, electrical resistivity values between approximately 200 and 700 µΩ cm were recorded.

Effects of nitrogen partial pressure on titanium oxynitride films deposited by reactive RF magnetron sputtering onto PET substrates

Titanium oxynitride (TiNxOy) films have been deposited onto polyethylene terephthalate (PET) substrates by reactive radio frequency (RF) magnetron sputtering. The influence of the nitrogen (N2) partial pressure in the discharge atmosphere, with a set pressure of 0.133 Pa, was examined. Other deposition conditions were held constant. The deposition rate of the films, which exhibit an island-type morphology, was found to decrease with increasing N2 partial pressure. This concurred with an increase in the surface roughness at higher N2 partial pressure. The TiNxOy films deposited at N2 partial pressures from 0.26×10−1 Pa to 0.8×10−1 Pa possess Ti:N:O ratio of about 1:0.9:0.8 to 1:1.2:0.7. At the lowest N2 partial pressure of 0.26×10−1 Pa, the water vapor (WV) and oxygen transmission rates (OTR) of the TiNxOy films reached values as low as 0.31 g/m2-day-atm and 0.62 cc/m2-day-atm, respectively; these values are about 16 and 50 times lower than those of the uncoated PET substrate.

Effects of nitrogen partial pressure on microstructure, morphology and N/Ti ratio of TiN films deposited by reactive magnetron sputtering

TiN films were deposited on Si(111) substrates at different nitrogen partial pressures with reactive magnetron sputtering. The crystal structure and preferred growth orientation of the films were determined using X-ray diffraction (XRD) analysis. Their morphology and composition were analysed using field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS). It is found that with the increase in nitrogen partial pressure, the growth of TiN films varies from the {111} preferred orientation to the {100} preferred orientation and the deposition rate of TiN films decreases. When the {111} preferred orientation is presented, TiN films reveal a kind of surface morphology of triangular pyramid with right angles; while the {100} orientation is dominant, TiN films characterise another kind of domelike surface morphology. Furthermore, the N/Ti ratio of the TiN films first increases, then decreases and increases again as nitrogen partial pressure enlarges.

Effects of nitrogen partial pressure on electrical properties and thermal stability of TiAlN films by ion beam sputter deposition

TiAlN films prepared using ion beam sputter deposition (IBSD) method are planed to be used as both the bottom electrode and diffusion barrier for a metal-insulator-metal (MIM) (Ba,Sr)TiO 3 (BST) capacitor in our study. We had shown the effects of ion beam voltage, substrate temperature on electrical properties, and thermal stability of TiAlN films in our previous study. In this paper, effects of nitrogen partial pressure ( P N2) during the IBSD process on TiAlN films properties and their effect on the electrical resistivity and thermal stability were investigated. It was found that P N2 affects the crystallographic structure, crystallinity, and composition of the films, resulting in varied performance in electrical resistivity and thermal stability. As P N2 increased, the degree of predominance in the (200) plane and the crystallinity of films decreased, resulting in the increase of electrical resistivity. It is believed that the diminishing degree of predominance in the (200) plane and the crystallinity of the films can be attributed to a decreased kinetic energy of adatoms with increasing P N2. Changing the amount of P N2 also affected the composition of deposited films. Thermal stability decreased with decreasing Al content and the crystallinity of films. It is worth mentioning that due to the dense film quality nature of the IBSD method, the TiAlN films deposited under optimum conditions ( P N2 = 4.4 × 10 −3 Pa) exhibited good thermal stability up to 700 °C in an oxygen atmosphere and the resistivity remained lower than 500μΩ × cm.