Plasma Sputtering Deposition Research Articles

Effects of High D.C. Hias Voltage on the Properties of Diamond-Like Carbon Films

ABSTRACTDiamond-like carbon (DLC) films were synthesized using pulsed plasma sputtering deposition techniques. Microscope and Raman scattering techniques were used to study the effects of bias voltages on the properties of diamond-like carbon films. With d.c. bias voltage up to 1000V, the smooth and thick DLC films together with a few nanoparticles were obtained. An increase of the d.c. bias voltage up to 2000V yielded thicker DLC films but its surface became slightly rough and size of particles became large. The crystalline properties of these particles were studied. A tiny diamond peak from Raman spectrum was also observed.

Synthesis and Control of Nano-Scale CN Particles and its Distributions

ABSTRACTMicro-scale to nano-scale carbon nitride (CN) particles were prepared by using plasma sputtering deposition technique. The preferred orientation of nanoscale CN particle distributions was obtained. Particles have been examined by using both Scanning Electron Microscopy (SEM) and Raman scattering (RS) spectroscopy. Setting bias voltage up to 5 kV, plasma-sputtering deposition gave rise to several ring (diameters: 2.4, 3.2, and 4.4 mm) patterns of particle distributions where many small groups of nanoscale particles were observed. Each group of these particles appeared in a sunflower type of distribution, in which the biggest (85 nm) particle at the center was surrounded by many small sizes (30 nm) of CN particles. Disk type of the particles with a diameter of 10 μm was also observed at different experimental conditions. Typical G, D bands and C=N band in the Raman spectra of the samples were identified. The intensity of the D bands obviously varied at the different deposition conditions.

QUICK SYNTHESIS OF CARBON NITRIDE FILMS BY NEW DC HOLLOW CATHODE PLASMA SPUTTERING DEPOSITION TECHNIQUE

High N content of carbon nitride films are quickly deposited onto Si (100) substrates at room temperature by using DC hollow cathode plasma sputtering deposition technique. The deposition rate is up to 283 nm/min at the bias voltage of 400 V. The properties of the films are characterized by using XPS, Raman (scattering) and Fourier transformation infrared (FTIR) spectroscopy. Experiments results provide direct evidences that the structures of CN films can be controlled by regulating bias voltages. The maximum sp3 C – N concentration up to 0.73 is obtained. Raman data is used to confirm XPS results. FTIR of the films clearly show C – N and C = N components (1000–1800 cm-1) together with a tiny peak C ≡ N (2181 cm-1). By reducing particle energy and substrate temperature, we have succeeded in suppressing the mechanisms of losing N -contain species during deposition, and achieved a large amount of sp3 bonds of CN films.

Magnetoresistance analysis of nanoscale magnetic correlation in cosputtered Fe/sub 100-x/Ag/sub x/ films

Nanogranular films of composition Ag/sub 100-x/Fe/sub x/(x: 10, 14, 20, 26, 30 at %) were prepared by dc plasma sputtering deposition. All films exhibit a negative magnetoresistance whose intensity decreases monotonically with temperature, with no apparent saturation up to 50 kOe. A magnetic correlation range R/sub m/ is obtained from analysis of the GMR versus M/M/sub S/ curves. The role of interparticle correlation is investigated as a function of both Fe concentration and temperature.

RF Plasma Sputtering Deposition of Hydroxyapatite Bioceramics: Synthesis, Performance, and Biocompatibility

AbstractSummary: Hydroxyapatite (HA) coatings have numerous applications in orthopedics and dentistry, owing to their excellent ability to promote stronger implant fixation and faster bone tissue ingrowth and remodeling. Thermal plasma spray and other plasma‐assisted techniques have recently been used to synthesize various calcium phosphate‐based bioceramics. Despite notable recent achievements in the desired stoichiometry, phase composition, mechanical, structural, and biocompatible properties, it is rather difficult to combine all of the above features in a single coating. For example, many existing plasma‐sprayed HA coatings fall short in meeting the requirements of grain size and crystallinity, and as such are subject to enhanced resorption in body fluid. On the other hand, relatively poor interfacial bonding and stability is an obstacle to the application of the HA coatings in high load bearing Ti6Al4V knee joint implants. Here, we report on an alternative: a plasma‐assisted, concurrent, sputtering deposition technique for high performance biocompatible HA coatings on Ti6Al4V implant alloy. The plasma‐assisted RF magnetron co‐sputtering deposition method allows one to simultaneously achieve most of the desired attributes of the biomimetic material and overcome the aforementioned problems. This article details the film synthesis process specifications, extensive analytical characterization of the material's properties, mechanical testing, simulated body fluid assessments, biocompatibility and cytocompatibility of the HA‐coated Ti6Al4V orthopedic alloy. The means of optimization of the plasma and deposition process parameters to achieve the desired attributes and performance of the HA coating, as well as future challenges in clinical applications are also discussed.SEM image of differentiated cells on HA bioceramics deposited by plasma sputtering, after a two‐day incubation period.magnified imageSEM image of differentiated cells on HA bioceramics deposited by plasma sputtering, after a two‐day incubation period.

Plasma sputtering deposition of platinum into porous fuel cell electrodes

Platinum is deposited into porous carbon materials relevant for fuel cell electrodes using plasma sputtering techniques. The resulting platinum concentration profile extends up to 2 µm into the porous carbon and is well fitted by a generalized stretched Gaussian function, which displays the non-thermal nature of the penetration process. Platinum deposits are observed to grow as clusters. On the outermost carbon particles, platinum nano-cluster sizes of 3.5 nm have been measured. In tests using actual PEM fuel cells, current densities as high as 1000 mA cm−2 have been obtained at 400 mV with 25 cm2 plasma electrodes. This compares favourably with commercially available electrodes but the present electrodes have a platinum density 4.5 times lower and hence can be considered to be significantly more efficient.

Proximity magnetoresistance in Ag 70 Fe 30 and Ag 74 Fe 26 cosputtered granular films

Granular films of composition Ag70Fe30 and Ag74Fe26 were prepared by dc plasma sputtering deposition in Ar atmosphere on Si substrates. Magnetization and magnetoresistance were measured between 2 K and 270 K. Both films exhibit a negative magnetoresistance (MR). The MR vs. reduced magnetisation curves are characterised by a box-like behavior, as already observed in magnetic systems with competing interactions. A standard analysis indicates that in both systems individual Fe nanoparticles are magnetically correlated over large distances. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Plasma deposition of constrained layer damping coatings

Plasma techniques are used to generate constrained layer damping (CLD) coatings on metallic substrates. The process involves the deposition of relatively thick, hard ceramic layers on to soft polymeric damping materials while maintaining the integrity of both layers. Reactive plasma sputter-deposition from an aluminium alloy target is used to deposit alumina layers, with Young's modulus in the range 77–220GPa and thickness up to 335 μ, on top of a silicone film. This methodology is also used to deposit a 40μ alumina layer on a conventional viscoelastic damping film to produce an integral damping coating. Plasma CLD systems are shown to give at least 50 per cent more damping than equivalent metal-foil-based treatments. Numerical methods for rapid prediction of the performance of such coatings are discussed and validated by comparison with experimental results.

Optical properties of tungsten and titanium oxide thin films prepared by plasma sputter deposition

Tungsten oxide and titanium oxide thin films were prepared by RF reactive magnetron sputter deposition. The stationary and rotating substrate holders were applied to analyze the rotating effect. The optical properties and thicknesses of oxide films were determined by a proposed optical model and the measured transmittance spectra. The dispersed refractive indices of thin films have a wide range distribution in different sputtering conditions. In the situation of rotating substrate holder, the refractive index was lower than that of the stationary substrate holder. Also, amorphous TiO2 structure can be prepared by using rotating substrate holder. The transmittance spectrum of crystalline TiO2 reveals that the textured structure on the film surface affects the transmittance characteristic.

Nano-Columnar Mg Thin Films Created by Plasma Sputter Deposition for Improved Hydrogen Kinetics and Storage Properties

ABSTRACTThe hydrogen storage properties of nanostructured Mg and MgH2 thin films were studied as created by Ar and Ar+H2 plasma sputter deposition. Columnar structures with typical widths of ∼120 nm are observed with their long columnar axis extending throughout the thickness of the films. Applying substrate bias voltages during deposition results in narrower columns. A concomitant reduction in hydrogen desorption temperature from 400 °C to 360 °C is observed. Capping the Mg films with a ∼100 nm thin Pd layer leads to significantly reduced hydrogen desorption temperatures of ∼200 °C induced by the catalytic activity of the Pd cap layer. Also, hydrogen permeation of the films is strongly improved. The rate-determining factor is found to be the dissociation of the hydrogen molecules. Optimum hydrogen loading conditions of the Pd/Mg films were obtained just above ∼200 °C at hydrogen pressures of 0.25–1.0 MPa, resulting in hydrogen storage capacities in the range of 4–7 wt%.

Aluminium oxide microchannel plates

Microchannel electron multipliers of a new type are proposed - anodic alumina microchannel plates (MCP). They implement the conventional concept of lead glass microchannel plate with a new material - anodic aluminium oxide. Anodic alumina is a very suitable material for microchannel plates due to presense of natural microchannels. Diameters of these channels lie in the range of 0.02 – 0.5 μm, channels of greater diameter can be easily produced by means of additional processing based on the presence of intrinsic microchannel structure. We have produced MCPs with channel diameters 0.2 – 8 μm and thickness 40 – 150 μm. We have also developed two methods of deposition of conductive and emissive films inside MCP channels: plasma sputtering and liquid-phase deposition from metallo-organic precursors. MCP samples with NiOMgO and CuCuOBeOMgO coatings have demonstrated promising results. Alumina MCP potentially have serious advantages over traditional lead glass MCP: they are much cheaper, large area plates (hundreds of cm2) can be easily produced, spatial resolution can be much better (due to smaller channel diameter).

Radio frequency magnetron sputtering deposition of calcium phosphate coatings: The effect of resputtering on the coating composition

Radio frequency magnetron plasma sputtering deposition is a fairly complex deposition method. Deposition of the film is influenced by the energetic bombardment of several species, like energetic electrons, neutrals, ions from the sputtering target and the plasma, and ultraviolet light. In this work we study the origin and the degree of (preferential) resputtering of species from a calcium phosphate ceramic film during the deposition process. We found that negatively charged oxygen is mostly responsible for the resputtering phenomena that occur. The degree of resputtering was determined by comparing the amount of material deposited behind and at the position of an aperture, which was positioned between the sputtering target and the substrate. The degree of resputtering can be derived, because the material behind the aperture is almost completely protected from bombardment by negatively charged oxygen. We found that at low Ar pressure, more than half of the material deposited is resputtered, preferentially P. Resputtering of the coating decreases with an increase in Ar pressure. An explanation for this may be that more negatively charged, energetic oxygen is ejected from the target at low Ar pressure, while at high Ar pressure more neutral, less energetic, oxygen is ejected. The former gives a higher resputtering rate.

SANS measurements with polarised neutrons on FeAg magnetic granular samples: compositional and magnetic morphology

We have performed small angle neutron scattering measurements with polarised and non-polarised neutrons on FeAg magnetic systems prepared by plasma sputtering deposition with the co-sputtering method. We have prepared various samples with an iron content ranging from 10% to 30% and for iron concentration up to 20% they display a superparamagnetic behaviour. Particular attention has been dedicated to these systems, in order to investigate the evolution of granular phase morphology with iron content. The data collected with polarised neutrons can be interpreted in terms of the presence of nanosized particles surrounded by non-magnetic regions. Our data also indicate that samples “magnetic” morphology is greatly affected by iron percentage while the compositional shows negligible modifications.

Tuning growth from clusters to continuous ultrathin films: Experiments and molecular dynamics simulations of Pd plasma sputter deposition

Plasma sputter deposition experiments and simple molecular dynamics calculations are performed for highlighting the effects of plasma ions and kinetic energy of palladium atoms on the morphology of thin films. A transition between cluster and continuous film growth is observed. It is attributed to the kinetic energy of the depositing sputtered palladium atoms and to high binding energy trapping sites resulting from the effects of ions incident on the surface during deposition. These high binding energy trapping sites act as additional nucleation centres that are allowed to be visited by the diffusing Pd atoms.

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.

Comparative study of copper films prepared by ionized metal plasma sputtering and chemical vapor deposition in the Cu/TaN/SiO2/Si multilayer structure

This work investigated the properties of ionized metal plasma (IMP) deposited copper (Cu) and chemical vapor deposited (CVD) Cu on IMP-TaN (tantalum nitride) diffusion barrier in the Cu(200 nm)/TaN(30 nm)/SiO2(250 nm)/Si multi-layer structure. The IMP-Cu film deposited on IMP-TaN had a preferred orientation (220) with a grain size of around 30 nm and roughness (RMS) of ∼1.391 nm, while the CVD-Cu had a (111) preferred orientation with a grain size around 170 nm and roughness (RMS) of ∼15.416 nm as determined by atomic force microscopy (AFM) and x-ray diffraction (XRD) analyses. Thermal stability study of the structures was also performed by sheet resistance measurements, scanning electron microscopy (SEM), XRD and Rutherford backscattering spectroscopy (RBS). These results revealed that IMP-Cu on IMP-TaN has higher thermal stability, less intermixing and/or agglomeration than CVD-Cu on IMP-TaN at the same annealing temperatures. The higher thermal stability of IMP-Cu than CVD-Cu can be accounted by their difference in microstructure. The failure mechanisms of IMP-Cu and CVD-Cu in multiplayer structure were also discussed.

Sheet resistance nonuniformity for ionized titanium deposition

A combination of recipe power and pressure in an ion metal plasma sputter deposition chamber has reduced average within-wafer sheet resistance nonuniformity approximately 40% to a value of 3.1%±0.2%. This result was obtained for a new polished target and nonknurled coil assembly operated over one coil life.

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.

Electrical characterization of a dc secondary discharge created during plasma sputtering deposition of palladium thin films

Good quality Pd thin films (for catalysis application) can be obtained by a low-pressure plasma sputtering method. The metal atom source is a helicoidal wire which is negatively biased so that argon ions created in a high frequency plasma are attracted and gain sufficient energy to induce sputtering. Depending on the experimental conditions (gas pressure, wire bias voltage), the sputtering process occurs in different regimes corresponding to either the presence of a simple cathodic sheath or the breakdown of an hollow cathode type discharge inside the helix. Since the flux of metal atoms condensing onto the substrate depends on the sputtering characteristics, it is of particular interest to study the formation of this secondary discharge (breakdown voltage and density profile). This is carried out by measuring the Langmuir saturation current profile inside and around the helix, and correlating the results with the determination by Rutherford backscattering spectroscopy analysis of the deposition rate on a SiO2 substrate. We also present density profiles of the argon plasma along the main axis of the reactor, which show that the flux of argon ions onto the substrate is not affected by the nature of the helix discharge. Finally, the ability to extend the range of deposition conditions (especially the ion flux to metal atom flux ratio) by using the helix diameter as an additional parameter is discussed.

Comparison of Pd/(Bulk SiC) Catalysts Prepared by Atomic Beam Deposition and Plasma Sputtering Deposition: Characterization and Catalytic Properties

Pd on SiC catalysts have been prepared using two different physical processes: atomic beam deposition (ABD) and plasma sputtering deposition (PSD). Whatever the method, Pd deposition (ranging between 0.3 and about 12 monolayer equivalent) yields thin metal adlayers. However, the catalysts prepared by ABD exhibit a 2D-like growth, with a strong metal support interaction which remains even for the highest Pd contents investigated. At lower Pd content the presence of adatoms and/or small nuclei in strong interaction with the SiC support is evidenced for samples prepared by PSD; but increasing the Pd content of PSD samples yields a rapid growth of 3D Pd particles which have the typical properties of bulk palladium. While the ABD catalysts exhibit good activity toward the 1,3-butadiene hydrogenation reaction, whatever the Pd content, PSD catalysts with low Pd content were quite inactive and/or strongly deactivated. However, at higher Pd content the PSD technique produces rather good catalysts.