Plasma Sputtering Technique Research Articles

Amorphous carbon coated stainless separator for PEFCs

An SUS316L stainless steel separator was coated with amorphous carbon by using an electron cyclotron resonance (ECR) plasma sputtering technique, and used in a polymer electrolyte fuel cell (PEFC). Characteristics of this carbon film were investigated with Raman spectroscopy and XPS. Quantitative depth profiles and chemical depth profiles of the deposited carbon layer were measured with GD-OES and XPS, respectively. The contact resistivity between a carbon paper and the carbon coated SUS316L steel was also measured. The performance of PEFC single cells assembled with carbon coated SUS316L separators, uncoated SUS316L separators, and conventional carbon separators were compared. The results revealed that an assembled PEFC having carbon coated SUS316L separators provided better performance than one having uncoated SUS316L, and the PEFC showed comparable performance to one having conventional carbon separators.

Structural, optical and electrical peculiarities of r.f. plasma sputtered indium tin oxide films

In this work the influence of the deposition conditions on the structural, electrical and optical properties of the ITO films was studied. Films were deposited by r.f. plasma sputtering technique in Ar and varying Ar + O 2 gas mixtures, with and without substrate heating. Transmittance and reflectance of the films were measured in the range 350–2500 nm; the refractive index ( n) and the extinction coefficient ( k) were calculated by the spectral data simulation. The sheet resistance of the films was measured by four-point probe method. X-ray diffraction analysis was performed to study the texture of the films. Threshold behaviour was observed in the optical and electrical properties of ITO films deposited in Ar + O 2 atmosphere at a certain oxygen concentration determined by a fix combination of all other deposition conditions. A schematic diagram for the change of the film properties versus composition was suggested, which explains the obtained results.

Optical and electrical characterization of r.f. sputtered ITO films developed as art protection coatings

Transparent and conductive tin-doped indium oxide (ITO) films have been prepared by r.f. plasma sputtering technique in Ar and Ar + O 2 gas mixture. The influence of the deposition conditions, film thickness, and substrate heating, as well as the post-annealing treatment on the optical and electrical properties of the ITO films has been investigated. The present study has extended the optical behaviour characterization of the ITO films in a wide UV–VIS–IR spectral region in addition to the comprehensive optical studies of this material at shorter wavelengths. The optical constants: refractive index ( n), extinction ( k) and absorption ( α) coefficient, and the optical band gap ( E go) have been calculated for the ITO films in the spectral range between 350 and 2500 nm. A combination of several well-known theoretical models has been applied to describe precisely the complex optical behaviour of ITO films in separate spectral parts. In this approach, a good overlapping between the experimental and the simulated spectra in the whole investigated spectral region has been achieved. The deposition conditions and the optical and electrical properties of the ITO films have been optimized with respect to the requirements for their applications in art protection coatings.

固体高分子型燃料電池用炭素被覆ステンレス製セパレータの開発とその発電特性

Conductive amorphous carbon was coated on the stainless steel separators by using electron cyclotron resonance (ECR) plasma sputtering technique. The carbon-coating reduced contact resistance between carbon paper and stainless steel substrate by two orders of magnitude. The carbon-coating also enhanced corrosion resistance of the stainless steels. Polarization performances of the polymer electrolyte fuel Cell (PEFC) using the carbon-coated SUS316L and SUS329J4L separators were comparable with that using the conventional carbon separator.

Preparation and characterization of ilmenite-hematite thin films

Ilmenite-hematite solid solution (Fe 2− x Ti x O 3) is one of the candidates for practical magnetic semiconductors with the high Curie temperature ( T C). We have successfully prepared well-crystallized and epitaxial Fe 1.4Ti 0.6O 3 films by using a reactive helicon plasma sputtering technique. The structural characterizations indicated that the films had the order structure ( R 3 ¯ symmetry), where Ti- and Fe-rich layers were stacked alternately along the c-axis, without any secondary phase. The subsequent annealing of the films in vacuum at 700 °C promoted the R 3 ¯ symmetry. Only the films having the good R 3 ¯ symmetry had large ferrimagnetic moments at room temperature. The resistivities of the films clearly showed semiconducting behavior, i.e., logarithmic resistivity showed a monotonous increase with increasing the inverse temperature. The minimum room temperature resistivity of the films was about 10 −1 Ω cm. From the Hall effect measurement all films had n-type conduction. The carrier concentration was estimated to be about 10 19–10 21 cm −3, depending on the annealing conditions.

Postannealing effect on pseudobilayer HfO2∕HfSixOy∕Si gate oxides formed by an inductively coupled sputtering process

Pseudobilayer HfO2∕HfSixOy gate dielectrics in metal-oxide-semiconductor devices were prepared using an inductively coupled rf plasma sputtering technique. This sputtering method was designed to improve the uniformity and efficiency of formation of high-quality gate dielectrics at room temperature. Crystallization of the gate dielectrics was easily controlled from amorphous to monoclinic by varying the external power from 0to60W at RT. The chemical bond states of the interfacial layers in the as-deposited and postannealed samples were analyzed with an x-ray photoelectron spectroscopy (XPS) system. The XPS results revealed that the interfacial layers of the as-deposited and annealed samples were hafnium silicide and hafnium silicate, respectively. Compared with the as-deposited sample, the pseudobilayer HfO2∕HfSixOy gate dielectric annealed at 750°C yielded excellent electrical characteristics due to the hafnium silicate interfacial layer. The dielectric constant and leakage current of the postannealed samples were about 15 at 100kHz and less than ∼10−6A∕cm2 at −1.5V, respectively.

Novel Nanopyramid Arrays of Magnetite

Pvramid-like Fe3O4 nanostructures (see Figure) are formed over large areas on alpha-Fe2O3(0001) substrates using a plasma-sputtering technique. No catalysts or templates are used in the reaction process. This nanostructure resembles Egyptian pyramids, possessing many layers and standing perpendicular to the substrate surface. These structures may have potential applications in constructing nanoscale magnetic and high-density storage devices.

Preparation and characterization of epitaxial FeTiO3+δ films

Abstract Epitaxial FeTiO3+δ(0 0 1) films were prepared on α-Al2O3(0 0 1) substrates by helicon plasma sputtering technique. Structure and magnetic properties of FeTiO3+δ film were largely dependent on the residual oxygen pressure (PO2) during the sputtering deposition. The films prepared at lower PO2 had an ilmenite ( R 3 ) structure, while a corundum ( R 3 c ) structure was observed in the case of higher PO2. The oxidation state of Fe in FeTiO3+δ films changed monotonically from Fe2+ to Fe3+ with increasing the PO2. The films with the R 3 symmetry were ferrimagnitic at low temperature, while the nonstoichiometric FeTiO3+δ with the R 3 c symmetry were antiferromagnetic at room temperature.

Nucleation and initial growth of platinum islands by plasma sputter deposition

The nucleation and islands growth of platinum have been followed from an early stage through to complete substrate coverage. Thus, this study of initial stages of thin film growth has allowed to improve the understanding of growth mechanisms and to control the final nanomaterials structure. In the presented deposition method, the metal atom source is a negatively biased metal wire submitted to the bombardment of ions created in HF plasma. The originality of this plasma sputtering technique is that in addition to the metal atom flux, the substrate surface is submitted to a high flux of low energy ions, inducing a high atomic surface mobility and modifying the growth mode with respect to conventional deposition techniques (magnetron sputtering or evaporation). Platinum deposits have been investigated by ex situ characterisation techniques: grazing incidence-small angle X-ray scattering (GISAXS) and X-ray diffraction (GIXD) in conjunction with transmission electron microscopy (TEM). Using morphological parameters as coverage rate, islands number density and islands size, different mechanisms (scale laws, islands mobility, coalescence, etc.) governing the growth are described vs. Ar ion and Pt atom energies and fluxes.

Nonstoichiometry of Epitaxial FeTiO3+δFilms

ABSTRACTEpitaxial thin films of (001)-oriented FeTiO3+δwere prepared on α-Al2O3(001) single crystalline substrates by helicon plasma sputtering technique. The FeTiO3+δfilms had large oxygen nonstoichiometry, which seriously depended on both substrate temperature and oxygen pressure during the sputtering deposition. The valence states of Fe ions in FeTiO3+δchanged monotonically from Fe2+to Fe3+with decreasing the substrate temperature from 900 to 400°C or with increasing the oxygen pressure from 0.9 to 1.8×10-6Pa. The change of Fe valence states from Fe2+to Fe3+induced the magnetic phase transition only for the films prepared at 900°C. The films containing Fe2+were paramagnetic while those with Fe3+were antiferromagnetic at room temperature. The oxygen nonstoichiometry of the FeTiO3+δfilms was probably produced by cation vacancies and disarrangement of Fe3+and Ti4+ions, which randomly occupied both interstitial and substitutional sites of the FeTiO3related structure.

Pd nanoclusters grown by plasma sputtering deposition on amorphous substrates

In this work, we study the deposition of palladium by a non-conventional plasma sputtering technique. The metal atom source is a biased wire which is sputtered by argon ions present in an HF-excited plasma. Two energetic plasma species (ions and metastable atoms) impinge onto the substrate surface during deposition and thus, may influence the growth. The flux of metastable atoms can be evaluated to 10 14 atoms/cm 2 with a potential energy of 12 eV. Electrical measurements of the plasma performed by the Langmuir probe allow the evaluation of the ion flux. It is of the order of 10 14 ions/cm 2 s for a kinetic energy of 50 eV. The respective effect of both species cannot be separated but, since ions carry higher energy, they are expected to play the major role. Thus, comparison is made with conventional ion beam-assisted deposition techniques, for which the ion flux vs. metal atom flux ratio is low (values ≤0.1 against 10 in plasma sputtering technique) and the incoming ion energy is high: of the order of hundreds or thousands of electron volts. Information on the film growth in these particular conditions are obtained by transmission electron microscopy (TEM) analysis of deposits performed on carbon membrane (coating copper grids) and by grazing incidence small angle X-ray scattering (GISAXS) characterization of Pd/amorphous SiO 2 deposits. In the present plasma conditions (100 mTorr argon pressure and −100 V wire bias), 3D clusters are found to be formed which grow in size and coalesce to form meandering islands. After the coalescence step, when the fractional covered area is sufficiently high, it is evidenced that the simultaneous energetic species flux causes a reorganization of the meandering aggregates, and further, the formation of more compact islands composed of bigger elementary clusters. This is attributed to a rise of the mobility of metal atoms and small clusters under bombardment.

Field-emission properties of diamond grains grown on textured Fe/Si substrates

Diamond grains were produced by the hot-filament chemical-vapor deposition technique using a mixture of CH4/H2 as the synthesis gas. The Si substrates were textured (random pyramids) by chemical etching before growth of diamond grains, because emission of electrons is facilitated at the top of the pyramids. In order to increase the diamond nucleation density, an iron thin film (Fe) was deposited on the textured Si substrate by a radio-frequency plasma sputtering technique. Moreover, partial iron thin films (20% surface coverage) were fabricated for application as field emitter displays using a metal mask. The relationship between the nucleation density and the thickness of the iron films has been investigated by scanning electron microscopy (SEM). The samples were placed in a high-vacuum chamber with a pumping system and the emission current was measured as a function of the applied voltage. The voltage–current (V–I) characteristics were estimated for the field emitter. In order to etch nondiamond components, these samples were etched by O2 and CF4 plasmas. SEM observation revealed that diamond growth is concentrated at the textured Fe/Si area. The nucleation density was 107 cm−2 on the textured Fe/Si area. On the plain textured Si substrate diamond growth could not be observed. Numberless tips were observed on the Fe/Si area after etching. The V–I characteristics revealed a current 10−8 Å at an applied voltage of 1.8 kV. The V–I characteristics could be enhanced by using the textured Fe/Si substrate.

Percolative growth of palladium ultrathin films deposited by plasma sputtering

Palladium ultrathin films have been deposited by a plasma sputtering technique. In a first step, small particles (mean diameter d<3 nm), homogeneously distributed on amorphous carbon membrane surfaces, are grown by surface diffusion of Pd atoms. Coalescence starts to form meandering compound clusters. Such Pd clusters, composing the islands, are still enlarging during the deposition. During the coalescence, a percolating network builds up with a measured percolation threshold around p c=0.7. The time evolutions of the mean size of the elementary and compound clusters are slightly modified when compared to vacuum deposition and theoretical predictions.

Ti/Al multilayer zone plate and Bragg-Fresnel lens.

By using a helicon plasma sputtering technique, a one-dimensional Ti/Al multilayer zone plate with an outermost layer width of 76 nm has been successfully fabricated. A Bragg-Fresnel lens has been made by combining this zone plate with a Ge(422) crystal. Comparison of the Ti/Al multilayer zone plate with the Ag/Al zone plate is discussed in terms of focusing efficiency.

Optimizing Sputtered Tin ARC Film Properties for Lithography of Sub-0.25μm Interconnect

ABSTRACTAdvanced interconnect fabrication may require alternative TiITiN processes, such as an ionized metal plasma (IMP) sputtering technique to deposit Ti/TiN liner for sufficient step coverage in high aspect ratio contacts/vias. Since TiN is also widely used as an anti-reflective coating on top of multilayer metal films, the optical properties of the TiN film are extremely important.In this paper, both IMP and standard PVD TiN films deposited on an aluminum layer are compared with respect to their lithography performance at exposure wavelengths of 365 nm (i-line) and 248 un (deep ultraviolet, or DUV). The measured optical constants of the two films were found to be very similar. The linewidth response of these two films at 365 nm was comparable; however, with DUV patterning, resist footing was observed on both films; but was especially severe with standard TiN. Differences in resist profile are explained in terms of the surface structure and density of the TiN film. By varying the conditions for deposition of IMP TiN (such as, RF bias, chamber pressure, etc.), the optical properties of the films may be varied. The impact of these varying film properties on DUV lithography is evaluated. Experimentally obtained linewidth response is compared with optical lithography simulations.

Optimization of giant magnetoresistance in ion beam sputtered Co/Cu multilayers

Ion beam sputtering (IBS) was used to prepare Co/Cu multilayer films within the first antiferromagnetic coupling range. Several preparation conditions were varied to optimize the giant magnetoresistance effect. We report the improvement of magnetoresistance by changing the sputtering gas from Ar to Xe, by finding an optimal substrate position and ion beam acceleration voltage, and by increasing the growth rate. A maximum magnetoresistance of 51% was achieved at room temperature in a stack with only 16 periods. The obtained improvements compared to previous efforts are discussed in terms of interface sharpness, layer homogeneity, and impurity incorporation. The main advantage of the established plasma sputtering technique, which still yields somewhat better results compared to IBS, appears to be a larger growth rate resulting in less impurity incorporation.

Nanofabrication of Multilayer Zone Plates by Helicon Plasma Sputtering

Multilayer zone plates whose outermost zone widths are less than 100 nm have been fabricated. Alternate deposition of Ag and Al layers has been performed using a helicon plasma sputtering technique, in which Ar gas pressure was less than 1×10-3 Torr, which is one order lower than in conventional magnetron sputtering. More than 100 Ag/Al layers were deposited, with the thickness of each layer being monitored and controlled by a computer. The multilayered plane was sliced vertically and thinned after the deposition. The multilayer zone plate combined with a crystal acts as a monochromatizing and focusing device for hard X-rays, i.e., a Bragg-Fresnel lens.

Quantum size effects on the optical and electrical properties of microcrystalline Si:H

We have fabricated microcrystalline Si:H by means of a new hydrogen plasma sputtering technique with a low substrate temperature of about 100 K. In spite of the low substrate temperature, the materials obtained are microcrystalline rather than amorphous. Surprisingly, the optical gaps are very large (up to 2.4 eV), and photoluminescence is visible at room temperature. These characteristic features are explained by the three-dimensional quantum size effects in isolated Si microcrystals.

Boron diffusion from a reactively sputtered glass source in Si and SiO2

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