Argon Target Research Articles

Structure and properties of reactively-sputtered Al xCoCrCuFeNi oxide films

Hex-element Al x CoCrCuFeNi ( x = 0.5, 1, 2) metallic and oxide films were deposited by sputtering homogeneous alloy targets in argon and argon–oxygen plasma, respectively. The metallic films are primarily composed of simple face-centered and/or body-centered cubic phases, while the oxide films comprise only a cubic-spinel crystalline phase. The aluminum content plays an important role in the structure and properties of both the metallic and the oxide Al x CoCrCuFeNi films. The lattice constant increases for both the face-centered and the body-centered cubic metallic phases while it decreases linearly for the spinel phase with increasing x value. The oxide films are nanocomposite in nature and their film hardness is enhanced by both aluminum and oxygen content with the highest hardness of 22.6 ± 1.6 GPa being achieved in this series of films.

Co-sputtered carbon-incorporated titanium oxide films as visible light-induced photocatalysts

Carbon-incorporated titanium oxide (TiO x C y ) films in anatase structure were deposited by co-sputtering titanium and graphite targets in argon and oxygen. The incorporation of carbon into TiO 2 retained the crystallinity of anatase phase and the carbon is a mix of both graphitic as well as substitutional in nature. The microstructure of the TiO x C y films consisted of columnar carbon-doped titania grains covered with graphitic carbon along the grain boundaries. The films exhibited absorption bands in the visible light region with an absorption edge red-shifted up to ∼ 450 nm corresponding to a band gap ∼ 2.7 eV and while absorption tails continued to above 700 nm. The films possessed outstanding visible light-induced photocatalytic properties in the reduction of silver ions, degradation of methylene blue and superhydrophilicity.

Analysis of magnetron sputtered boron oxide films

Boron oxide films were grown on silicon substrates by radio-frequency (rf) unbalanced magnetron sputtering of a boron target in argon–oxygen gas mixtures with different compositions. Microscopic analyses show that overall boron oxide films are amorphous. The film prepared at oxygen/argon flow rate ratio > 0.05 developed large crystallites of boric acid in localize areas of amorphous boron oxide matrices. These crystallites were unstable and at electron microscopic analysis they continuously transformed to a cubic HBO 2 phase and then completely vanished leaving an underlying amorphous boron oxide film behind. The analyses indicate the coexistence of B 6O, HBO 2 crystallites and amorphous boron oxide matrices. Fourier transform infrared (FTIR) spectra revealed spectral bands of BOH, BO, BOB and BH groups. Nanohardness and elastic modulus of a film prepared at low oxygen concentration approach 30 and 300 GPa, respectively. These parameters however vary with deposition conditions.

Structural and Mechanical Properties of (Al,Cr)N and (Al,Cr)SiN Coatings Reactively Sputter Deposited

AlCrN and AlCrSiN coatings were deposited on M2 steel by cosputtering of metallic Al-Cr (70–30 at.-%) and Si targets in reactive argon–nitrogen gas mixtures. The Si content in the film varied from 0 to 1.7 at.-%, as a function of the current applied on the Si target. The properties of these films have been determined by X-ray diffraction (XRD) and glow discharge optical emission spectroscopy (GDOES). Nanohardness test (NHT) and scratch tests have been used to determine their mechanical properties. All the coatings are amorphous (or nanocrystallised) with a dense glassy morphology and present a good adhesion. The mechanical tests have clearly shown the effect of the addition of Si on the properties of the coatings. Hardness and Young's modulus increase with the silicon content whereas the friction coefficient decreases.

Adhesion and Tribological Properties of Sputtered Polymer Thin Films with Thermally Stable Polymer Targets

Polymer thin films were sputtered with thermally stable polymer targets onto a copper and glass slide substrate with a conventional RF sputtering apparatus. Polymer structures and adhesion and tribological properties of these polymer thin films were evaluated. The pull strength between evaporated metal films and sputtered poly(tetrafluoroethylene) (PTFE) thin film was higher than that between evaporated metal thin films and the bulk PTFE. This difference was apparently due to differences in chemical bonding states between the sputtered PTFE thin film and the bulk PTFE. The PTFE thin films were sputtered at various conditions. Surface free energy of the PTFE thin films decreased with increase of fluorine content of the PTFE thin films. Although dispersion force component of the surface free energy slightly decreased, dipole force component dramatically decreased with increase of temperature of the substrate. Polymer thin films were sputtered onto copper substrate with two polyimide (Kapton-VTM and Upilex-STM) targets. Argon and nitrogen were introduced into the sputtering chamber for the sputtering gases. Sputtering rate of the polymer thin film with argon gas showed highest value at a pressure of 0.67 Pa. However, the sputtering rate with nitrogen gas showed highest value at a pressure of 8 Pa. Nitrogen content in the thin film sputtered with the nitrogen gas (N2 sputtered thin film) increased compared to that sputtered with argon gas (Ar sputtered thin film) and target material. Friction coefficient and wear durability of the N2 sputtered thin film were higher than those of the thin film sputtered with the Ar sputtered thin film. The pull strength between the N2 sputtered thin film and copper substrate was higher than that between the Ar sputtered thin film and copper substrate. In addition, the N2 sputtered thin film was introduced between the copper substrate and Ar sputtered thin film (Ar/N2/Cu laminate). The pull strength of this laminate showed higher value than that between the Ar sputtered thin film and copper substrate.

Comparative analysis of amorphous silicon and silicon nitride multilayer by spectroscopic ellipsometry and transmission electron microscopy

Amorphous silicon (a-Si) and silicon nitride (SiN) films were prepared on polished silicon wafers by radio frequency sputtering using silicon target in argon and nitrogen plasma. The process described here is simple and well suited for fabricating multilayer structures of films with different refractive indices. Optical models were developed to analyze the spectroscopic ellipsometry data measured on the multilayer structure. The dielectric functions of amorphous silicon and silicon nitride were modeled by the Tauc–Lorentz oscillator model and by the Cauchy dispersion model, respectively. A thick a-Si layer was prepared and measured to establish appropriate initial refractive index data for evaluation of measurements on multilayer stacks. The parameters of layers with identical materials in the layer stack were coupled to decrease the number of fitted model parameters. Refractive index spectra of a-Si and SiN as well as thicknesses of the multilayer structure were calculated from one measurement. The results of the ellipsometric analysis are in good agreement with transmission electron microscopy data.

Structural investigations of YSZ coatings prepared by DC magnetron sputtering

(ZrO 2) 1− x (Y 2O 3) x thin films were sputter-deposited from metallic targets in various reactive argon–oxygen gas mixtures. Structural investigations have been realised by X-ray Diffraction (XRD), Raman spectroscopy and Transmission Electron Microscopy (TEM). The coatings microstructure have been characterised by TEM and their morphology by Scanning Electron Microscopy (SEM) on brittle-fracture cross sections. Chemical compositions have been achieved by Electron Probe Micro-Analysis (EPMA) and by Energy Dispersive Spectroscopy (EDS). Finally, attention was paid to the film optical properties, as assessed via Optical Transmission Interferometry (OTI) as well as spectrophotometry. In a first part, we have studied the influence of the argon pressure on the chemical, structural and morphological properties of the coatings. In a second part, we have observed the effect of the yttria content on the structure of the films.

Titanium oxide thin films deposited by high-power impulse magnetron sputtering

Ionized physical vapor deposition processes are of great interest for surface modification because the flexibility of the thin film deposition process can be increased by ionizing the metallic vapor. Recently, high-power impulse magnetron discharges have been implemented to achieve high ionization rates. Thin films of titanium oxide have been deposited on glass and steel substrates using 450 × 150 mm rectangular titanium target in argon–oxygen atmosphere. The average power delivered to the plasma is ranging between 1.5 and 2 kW and peak current and voltage are respectively 200 A and 900 V. Films are characterized using Scanning Electron Microscopy, Grazing Incidence X-ray Diffraction and Optical Transmission Spectroscopy. One of the major findings is the presence of rutile deposited on steel substrate (even for 0 V bias grounded substrate) and the significant increase of the refractive index of the films deposited on glass compared to thin films deposited via conventional direct current bipolar pulsed magnetron sputtering. Films synthesized by high-power impulse magnetron sputtering are denser.

Hot electron jets from femtosecond heated plasmas at intensities of 1016–1017W/cm2

Solid target experiments carried out on copper targets with both p- and s-polarized 130 fs Ti:Sapphire laser pulses at intensities of 3 x 10 16 W/cm 2 indicate the presence of hot electron jets with electron energies of 80 to over 250 keV and cone angles of the order of 10 degrees at the higher energies with directions dependent on the incident polarization. For comparison, studies on an Argon cluster jet targets with 50 fs duration Ti:Sapphire laser pulses at vacuum intensity of 10 17 W/cm 2 indicated no detectable hot electron jet emission with electron energies above 50 keV. A 2D PIC simulation of the p-polarized solid target interaction predicts features similar to those observed experimentally.

A comparison of electrical properties of sputter-deposited electrolyte coatings dedicated to intermediate temperature solid oxide fuel cells

Solid electrolyte thin films of Yttria-Stabilised Zirconia (YSZ), Gadolinium-Doped Ceria (GDC) and Lanthanum-Molybdenum Oxide (LaMO x) are sputter-deposited or co-sputter-deposited on rotating substrates from metallic targets in reactive argon–oxygen mixtures. Their chemical and structural features are investigated by Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD) and their morphology is observed by Scanning Electron Microscopy (SEM) of brittle-fracture cross sections. Relationships are established with their electrical behaviour determined by means of Complex Impedance Spectroscopy (CIS). It is shown that the activation energy of the different electrolytes is consistent with the literature data after stabilisation of their microstructure by annealing around 800 °C.

Technique for direct detection of weakly interacting massive particles using scintillation time discrimination in liquid argon

Discrimination between electron and nuclear recoil events in a liquid argon scintillation detector has been demonstrated with simulations by using the differences in the scintillation photon time distribution between these classes of events. A discrimination power greater than 10 8 is predicted for a liquid argon experiment with a 10 keV threshold, which would mitigate electron and γ-ray backgrounds, including β decays of 39Ar and 42Ar in atmospheric argon. A dark matter search using a ∼2 kg argon target viewed by immersed photomultiplier tubes would allow a sensitivity to a spin-independent WIMP-nucleon cross-section of ∼10 −43 cm 2 for a 100 GeV WIMP, assuming a one-year exposure. This technique could be used to scale the target mass to the tonne scale, allowing a sensitivity of ∼10 −46 cm 2.

Nanocrystalline gamma alumina coatings by inverted cylindrical magnetron sputtering

Alumina coatings were deposited on glass, silicon and stainless steel substrates by magnetron sputtering of two cylindrical aluminum targets in argon–oxygen plasma using a mid frequency AC power supply operated at 41 kHz and 5 kW. No substrate heating was used during the deposition process. Reactive sputtering was carried out in the poisoned mode of the targets at low deposition rates of about 0.09 nm s − 1 . The coatings were characterized by X-ray diffraction studies and found to be nano-crystalline, γ-phase of aluminum oxide. The coatings thickness was measured using the optical interference effects in the UV–visible spectrum of thin films deposited on glass substrates. Thin film thickness after 4 h of reactive sputtering was found to be 1.3 μm. We further studied the oxidation resistance of the alumina coatings produced on stainless steel substrates at a temperature of 400 °C. Coatings were found to be completely stable at this temperature and prevented the oxidation of underlying stainless steel substrate.

Zinc treatment effects on corrosion behavior of 304 stainless steel in high temperature, hydrogenated water

Trace levels of soluble zinc(II) ions (30 ppb) maintained in mildly alkaline, hydrogenated water at 260 °C were found to lower the corrosion rate of austenitic stainless steel (UNS S30400) by about a factor of five, relative to a non-zinc baseline test [S.E. Ziemniak, M. Hanson, Corros. Sci. 44 (2002) 2209] after 10,000 h. Characterizations of the corrosion oxide layer via grazing incidence X-ray diffraction and X-ray photoelectron spectroscopy in combination with argon ion milling and target factor analysis, revealed that miscibility gaps in two spinel binaries—Fe(Fe 1− m Cr m ) 2O 4 and (Fe 1− n Zn n )Fe 2O 4—play a significant role in determining the composition and structure of the corrosion layer(s). Although compositions of the inner and outer corrosion oxide layers represent solvus phases in the Fe 3O 4–FeCr 2O 4 binary, zinc(II) ion incorporation into both phases leads to further phase separation in the outer (ferrite) layer. Recrystallization of the low zinc content ferrite solvus phase is seen to produce an extremely fine grain size (∼20 nm), which is comparable in size to grains in the inner layer and which is known to impart resistance to corrosion. Zinc(II) ion incorporation into the inner layer creates additional corrosion oxide film stabilization by further reducing the unit cell dimension via the substitution reaction 0.2 Zn 2 + ( aq ) + Fe ( Fe 0.35 Cr 0.65 ) 2 O 4 ( s ) ⇄ 0.2 Fe 2 + ( aq ) + ( Zn 0.2 Fe 0.8 ) ( Fe 0.35 Cr 0.65 ) 2 O 4 ( s ) The equilibrium constant for the substitution reaction is similar in magnitude to an estimate based on available free energies for FeCr 2O 4, ZnCr 2O 4, Fe 2+(aq) and Zn 2+(aq). This interpretation is consistent with the benefits of zinc treatment being concentration dependent.

Studies of structure and morphology of sputter-deposited stainless steel–nitrogen films

Stainless steel films doped with nitrogen were deposited on heated and unheated (100) silicon substrates by radio-frequency magnetron sputtering of an austenitic stainless steel target in argon and nitrogen gas mixtures, containing a range of nitrogen compositions. The evolution of phases, morphologies and grain structures in the resultant films was studied by X-ray diffraction and field emission scanning electron microscopy. It was found that, with increasing nitrogen composition in the gas mixture, the crystalline structure of the films deposited on the heated substrates changed from bcc ferrite (α), to nitrogen-stabilized fcc austenite (γ), then to distorted expanded austenite phase (γN) with nitrogen supersaturation, and finally to the newly discovered fcc ‘MN’ phase with ideal cubic symmetry and further enlarged lattice. On the unheated substrates, the phase-evolution trend was found to be different for % N2 above 10. For the 25% N2 film, amorphous phase formed along with the crystalline austenite and ferrite phases, while the percentage of amorphous content decreased when % N2 was increased to 50. This different trend was understood to be due to the role of increase in % N2 in decreasing the energy loss of sputtered species through collisions. The dependence of crystalline phase formation on the energy of sputtered species is less severe on the heated substrates. Although all the films deposited experienced three-dimensional fibrous growths, they exhibited different surface morphology and grain structure. There exists a correlation between film morphology and phase constituents, while grain size was influenced by the nucleation density and the energy and mobility of adatoms that are reduced due to nitrogen incorporation.

Microstructure, composition and oxidation resistance of nanostructured NiAl and Ni–Al–N coatings produced by magnetron sputtering

Nanostructured NiAl and Ni–Al–N thin films were RF magnetron sputtered from a NiAl compound target in different argon–nitrogen atmospheres. The structure and stoichiometry of as-deposited coatings were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Differential thermal analysis (DTA) was also conducted to study the oxidation kinetics of the films at high temperatures. Microstructural and compositional changes of the coatings after isothermal oxidation were investigated using XRD, SEM, and Rutherford backscattering spectrometry (RBS). The results show that: (1) denser and more completely crystallized Ni–Al–N thin films can be tailored through controlled ion bombardment during deposition, (2) nano-composite NiAl–AlN thin films were synthesized with nitrogen atomic concentrations up to 30%, and (3) the NiAl and Ni–Al–N coatings exhibited good oxidation resistance even at temperatures above 1273 K. The addition of AlN to NiAl resulted in decreased activation energies for oxidation. The oxidation study also revealed different rate controlling mechanisms for NiAl and Ni–Al–N (21.4 at.% N) films isothermally oxidized in air at 1273 K.

Efficient absorption and intense soft X-ray emission from gas cluster plasmas irradiated by 25-ps laser pulses

A highly efficient absorption is observed in multipicosecond laser pulse irradiation of argon and nitrogen gas cluster targets at moderate intensities of /spl sim/10/sup 15/ W/cm/sup 2/ using a 1.5 J/25 ps Nd : phosphate glass laser (/spl lambda/=1.054 /spl mu/m). Measurements of laser light absorption, side scattering, and extreme-ultraviolet (XUV) emission spectrum are performed for argon and nitrogen gases puffed through sonic or hypersonic nozzles in the pressure range from 10 to 60 bar. High values of 80%-85% of laser light absorption have been measured in both nitrogen and argon gas cluster plasmas. The X-ray line emission from argon plasma was /spl sim/ 30-40 times stronger than that from the nitrogen plasma, which is related to the formation of larger sized clusters in argon. The very high laser light absorption observed in these multipicosecond laser pulse irradiation experiments may be understood to be occurring due to intense heating of the near solid density clusters in the initial part of the laser pulse creating a plasma of a high degree of ionization, which continues to absorb the rest of the laser pulse energy through collisional processes during its expansion to subcritical densities.

Accelerating multiple scattering of the emitted electrons in collisions of ions with atoms and molecules

Double differential cross-sections for electron emission were measured in the collisions of N+ ions with N2, Ne and Ar targets in the 700–1500keV impact energy range. We studied the target atomic number dependence of the Fermi-shuttle type acceleration mechanism. The experimental double differential cross-sections are in good agreement with the theoretical values obtained from CTMC calculations for argon target. According to the calculations, multiple scattering contribution to the Ar spectra above 300eV is significant.

Characterization of rf sputtered TiO yS z thin films

Different titanium oxysulfide thin films were prepared by rf magnetron sputtering using two types of targets in a pure argon or mixed oxygen/argon atmosphere with a total pressure of 1 or 0.2 Pa. We have studied the influence of the sputtering conditions (target, total pressure, oxygen partial pressure) on the composition, the morphology and the local and electronic structure of our thin films. A set of complementary techniques (scanning electron microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS)) was used to characterize the thin films. Two types of films have been obtained: thin films prepared from TiS 2 target having a composition and a local structure close to TiS 3 and thin films obtained from TiS 2/TiS 3 target characterized by a composition and a local structure close to TiS 2. The complementary use of XPS and sulfur K-edge XAS spectroscopies has allowed us to evidence the coexistence of different microdomains into the thin films corresponding respectively to a pure sulfur, a pure oxygen or a mixed sulfur/oxygen environment.

Corrosion behavior of NiCrFe Alloy 600 in high temperature, hydrogenated water

The corrosion behavior of Alloy 600 (UNS N06600) is investigated in hydrogenated water at 260 °C. The corrosion kinetics are observed to be parabolic, the parabolic rate constant being determined by chemical descaling to be 0.055 mg dm −2 h −1/2. A combination of scanning and transmission electron microscopy, supplemented by energy dispersive X-ray spectroscopy and grazing incidence X-ray diffraction, are used to identify the oxide phases present (i.e., spinel) and to characterize their morphology and thickness. Two oxide layers are identified: an outer, ferrite-rich layer and an inner, chromite-rich layer. X-ray photoelectron spectroscopy with argon ion milling and target factor analysis is applied to determine spinel stoichiometry; the inner layer is (Ni 0.7Fe 0.3)(Fe 0.3Cr 0.7) 2O 4, while the outer layer is (Ni 0.9Fe 0.1)(Fe 0.85Cr 0.15) 2O 4. The distribution of trivalent iron and chromium cations in the inner and outer oxide layers is essentially the same as that found previously in stainless steel corrosion oxides, thus confirming their invariant nature as solvi in the immiscible spinel binary Fe 3O 4–FeCr 2O 4 (or NiFe 2O 4–NiCr 2O 4). Although oxidation occurred non-selectively, excess quantities of nickel(II) oxide were not found. Instead, the excess nickel was accounted for as recrystallized nickel metal in the inner layer, as additional nickel ferrite in the outer layer, formed by pickup of iron ions from the aqueous phase, and by selective release to the aqueous phase.

Carbon film deposition on polyethylene terephtalate by pulsed-plasma technology

Elastic amorphous carbon films were deposited by continuous and pulsed-plasma sputtering on polyethylene terephtalate (PET) for gas barrier applications. A study was done of the influence of the plasma parameters on the morphological, mechanical and structural properties of the films. Graphite was used as the sputtering target in argon–hydrogen RF plasmas. In the pulsed mode operation (on/off), pulse frequencies within the (1–100) kHz range were applied. Pulsing resulted in an enhanced deposition rate and in changes in the ion population composition of the plasma, namely, an increase of the hydrogenic ion proportion with the low frequencies. This influenced both the elasticity of the films and the disorder in the atomic structure. Correlations between the plasma process parameters and the permeation properties of the films to He were also established.