Sputtering Source Research Articles

Ferroelectric liquid crystal aligned on SiO2 thin films using ion‐beam deposition

Abstract— Results for a ferroelectric‐liquid‐crystal (FLC) display cell, aligned on inorganic SiO2 thin‐film surfaces by using oblique ion‐beam sputtering deposition on the substrates, is presented. A large deposition angle from 60° to 80° can be employed for the thin alignment layer, with thicknesses varying from 5 to 40 nm. Two types of uniform alignment, chevron (before electrical treatment) and quazi‐bookshelf (after electrical treatment), were studied. High‐quality alignment on large‐sized substrates was also easily be achieved because of the linear design of the ion‐beam sputtering source, which was previously a significant challenge for FLC on SiOx layers.

Structure of palladium nanoclusters for hydrogen gas sensors

Palladium nanoclusters produced in an inert gas aggregation/magnetron sputtering source are being used as building blocks for the construction of nano electronic devices with large surface to volume ratios that can be used as sensitive hydrogen gas sensors in fuel cells and in petrochemical plants. Grazing incidence X-ray diffraction (GIXRD) at the Stanford Synchrotron Radiation Laboratory (SSRL) and high resolution transmission electron microscopy (HRTEM) have been used to characterise the structure, lattice constant, particle diameter and oxide thickness of the palladium nanoclusters in order to understand the operation of these sensors.

Structure and mechanical properties of Ag-incorporated DLC films prepared by a hybrid ion beam deposition system

Ag-incorporated diamond-like carbon films were prepared on Si(100) wafers using a hybrid deposition system composed of an end-Hall-type hydrocarbon ion gun and a silver DC magnetron sputter source. The Ag concentration in the films was controlled by changing the fraction of Ar in the Ar and benzene reaction gas. The chemical composition, microstructure, atomic bond structure, and mechanical properties were investigated for Ag concentrations ranging from 0 to 9.7 at.%. When the Ag concentration was 0.1 at.%, the Ag atoms were fully dissolved in the amorphous carbon matrix without forming any second phase. Amorphous and crystalline silver particles appeared when the Ag concentration was 1.7 and > 6.8 at.%, respectively. It was found that the hardness was not sensitive to the Ag concentration in this concentration range. On the other hand, the residual compressive stress was strongly dependent on the chemical state of the incorporated Ag atoms. The mechanical properties are discussed in terms of the changes in the microstructure and atomic bond structure induced by Ag incorporation.

Experimental and simulational study of the operation conditions for a high transmission mass filter

The operation conditions of a double pulsed field mass filter were studied using both experiment and simulation. The mass filter consists of two pairs of parallel plates and operates on the time-of-flight principle. The study showed that the ions' beam deflection angle is a critical factor in optimizing the mass filter transmission efficiency. This angle is dependent on the accelerating voltage, ion mass, and horizontal velocity of the ions. The optimum operating conditions for the mass filter were found and used to study the mass distribution of palladium ions produced by a magnetron sputtering source. The study shows that this mass filter is suitable for technological applications because of its high transmission and wide mass range.

P‐113: Ferroelectric LC Aligned on SiO2 Thin Films Using the Ion Beam Deposition and its Applications

AbstractThe uniform alignment of Ferroelectric LCs (FLC) on inorganic thin film surfaces can be obtained using oblique ion beam sputtering deposition on substrates. Large deposition angle from 60° to 80 ° can be used for thin SiO2 alignment layer, which thickness can vary from 5nm to 40 nm. Two types of uniform alignment of “chevron” (before electrical treatment) and “quazi‐bookshelf” (after electrical treatment) were studied. The applications using this unique technology in low power consumption displays, fast switching color displays, future LCD‐TVs and fiber optics are discussed. High quality alignment on large size substrates is also easily achieved because of the linear design of the ion beam sputtering source, which is a big challenge for FLC on SiOx layers before.

Scrape-off layer transport and deposition studies in DIII-D

Trace C13H4 injection experiments into the main scrape-off layer (SOL) of low density L-mode and high-density H-mode plasmas have been performed in the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] to mimic the transport and deposition of carbon arising from a main chamber sputtering source. These experiments indicated entrainment of the injected carbon in plasma flow in the main SOL, and transport toward the inner divertor. Ex situ surface analysis showed enhanced C13 surface concentration at the corner formed by the divertor floor and the angled target plate of the inner divertor in L-mode; in H-mode high surface concentration was found both at the corner and along the surface bounding the private flux region inboard of the outer strike point. Interpretative modeling was made consistent with these experimental results by imposing a parallel carbon ion flow in the main SOL toward the inner target, and a radial pinch toward the separatrix. Predictive modeling carried out to better understand the underlying plasma transport processes suggests that the deuterium flow in the main SOL is related to the degree of detachment of the inner divertor leg. These simulations show that carbon ions are entrained with the deuteron flow in the main SOL via frictional coupling, but higher charge-state carbon ions may be suspended upstream of the inner divertor X-point region due to balance of the friction force and the ion temperature gradient force.

ToF‐SIMS depth profiling of a complex polymeric coating employing a C60 sputter source

AbstractA complex poly(vinylidene difluoride) (PVdF)/poly(methyl methacrylate) (PMMA)‐based coil coating formulation has been investigated using time‐of‐flight SIMS (ToF‐SIMS). Employing a Bi3+ analysis source and a Buckminsterfullerene (C60) sputter source, depth profiles were obtained through the polymeric materials in the outer few nanometres of the PVdF topcoat. These investigations demonstrate that the PVdF coating's air/coating interface is composed principally of the flow agent included in the formulation. Elemental depth profiles obtained in the negative ion mode demonstrate variations in the carbon, oxygen and fluorine concentrations within the coating with respect to depth. All three elemental depth profiles suggest that the PVdF coating bulk possesses a constant material composition. The oxygen depth profile reveals the presence of a very thin oxygen‐rich sub‐surface layer in the PVdF coating, observed within the first second of the sputter/etch profile. Retrospectively, extracted mass spectra (from the elemental depth profile raw data set) of the PVdF coating sub‐surface and bulk layers indicates this oxygen‐rich sub‐surface layer results from segregation of the acrylic co‐polymers in the formulation towards the PVdF coating air/coating interface. Molecular depth profiles obtained in both the positive and negative secondary ion modes provide supporting evidence to that of the elemental depth profiles. The molecular depth profiles confirm the presence of a sub‐surface layer rich in the acrylic co‐polymers indicating segregation of the co‐polymers towards the PVdF topcoats air‐coating surface. The molecular depth profiles also confirm that the PVdF component of the topcoat is distributed throughout the coating but is present at a lower concentration at the air‐coating interface and in the sub‐surface regions of the coating, than in the coating bulk. Copyright © 2007 John Wiley & Sons, Ltd.

Co-deposition of silver nanoclusters and sputtered alumina for sensor devices

Heterogeneous thin films may be beneficial for sensoring devices. The electrical conductivity of nanoscale metallic particles being embedded in a matrix of non conducting material should exhibit higher sensitivity to mechanical stress and strain compared to homogeneous films. The production of heterogeneous films may follow different routes. This paper describes the attempt to embed Ag nanoclusters emitted from a gas aggregation cluster source into a growing matrix of alumina originating from sputter sources. The characteristics of the cluster source are first resumed, with their mean masses ranging from approx. 1000 to 100,000 atoms per cluster. The expelled and soft landed clusters are extensively examined by transmission electron microscopy verifying their crystalline form. Yet the use of a radio frequency driven sputter source for the embed material destroys and annihilates the Ag clusters even at very low sputter power. If a reactive direct current sputter process is performed within an oxidising sputter gas instead, the Ag clusters are oxidised to different oxides, but they survive as crystalline entities as verified by X-ray diffraction investigations. A simple subsequent heat treatment reduces the Ag oxides to metallic Ag clusters.

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We present the fabrication process of straight-ridge Yb3+:Er3+ co-doped Al2O3 waveguides. Thin films are synthesized on silica-on-silicon wafers by middle frequency sputtering (MFS) and microwave ECR (MW-ECR) plasma source deposition. Waveguides are developed by reactive plasma etching employing BCl3 gas. Photoluminescence (PL) spectrum and gain measurements at 1.53 µm are investigated at room temperature: a net gain of 5.225 dB/cm is achieved from a 10.5-mm-long waveguide obtained by MFS, and 0.043 dB/cm is achieved from a MW-ECR with a 980-nm pump power of 62 mW.

Preparation and properties of W-containing diamond-like carbon films by magnetron plasma source ion implantation

W-containing diamond-like carbon (DLC) films were prepared on silicon wafers by a process combining reactive magnetron sputtering with plasma source ion implantation (PSII). A tungsten disc was used as a target for the sputter source. Ar/C 2H 2 mixed gas was introduced into the discharge chamber. Superposed negative high voltage pulses (− 10 kV, 100 Hz, 100 μs and DC − 0.5 kV) were applied to the substrate holder. The chemical composition of the films was determined using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Surface morphology was observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The film structure was characterized by Raman spectroscopy, X-ray diffractometry and high resolution transmission electron microscopy (HREM). Sheet resistivity of the films was measured by a four-point probe method. Furthermore, a ball-on-disc test was employed to obtain information about the frictional properties and sliding wear resistance of the films. The structure of the films changed from metal-containing DLC to a composite of metal-containing DLC and metal carbides with increasing metal content in the films. WC 1− X carbides were observed for films composed of higher amounts of W than 20 at.%. Around 10 nm diameter nanocrystallites of WC 1− X were observed by HREM. The sheet resistivity of the films decreased drastically with increasing metal content in the films. The tribological properties of the films were improved by metal element doping. A low friction coefficient 0.09 was derived for 0.5 at.% W-containing DLC film.

Predicting the long-term solar wind ion-sputtering source at Mercury

Maps of the precipitating solar wind proton flux onto Mercury's surface are constructed using a modified Toffoletto–Hill (TH93) model of the Hermean magnetosphere. Solar wind and IMF conditions around Mercury's orbit near aphelion and perihelion, respectively, were estimated by reanalyzing the Helios 40-s data for times when the spacecraft as in Mercury's orbital range (0.31–0.47 AU). Probability density estimates obtained in this way allow us to quantitatively predict the likely range of the ion-sputtering source as a function of true anomaly angle of the planet. Results indicate that the sputtering source along open fieldlines increases fourfold from aphelion to perihelion, and that significant precipitation along closed fieldlines is twice as likely at perihelion due to finite Larmor radius effects. We conclude that ion sputtering is comparatively more important as a source for the Hermean exosphere at perihelion.

Ion source refinement at VERA

This paper describes various modifications implemented at the 40-samples MC-SNICS Cs sputter source used at VERA. The pneumatic sample changer was replaced with a stepper motor drive, and also the adjustment collar for the vertical target wheel position was motorized. These two modifications allow now an automatic scanning of the target position with respect to the Cs-sputter beam. It also opens the way to use sample wheels holding more than 40 sample positions while keeping the original dimensions of the wheel. In order to hold the negative ion output constant, the control computer now regulates the Cs-capillary heater while the Cs-oven heater power supply stays fixed. Another modification was the replacement of the original conical ionizer with a spherical one, involving the enlargement of the diameter of the Cs-focus lens. This modification almost doubled the source output. To adapt the new ion optical geometry, we mounted a shield electrode in front of the target.

Towards the analysis of platinum group elements at low levels in insulating materials

The operating parameters for a high current caesium sputter source have been modified so that stable beams of anions can be obtained from natural non-conducting samples. This technique has been applied to the analysis of gold and platinum group elements in silicate matrices, particularly olivines. The handling of interferences resulting from the large number of molecular ions produced in such a target, and the effect of differences in the matrices of reference materials are discussed.

CAMS/LLNL ion source efficiency revisited

The Center for AMS, Lawrence Livermore National Laboratory (CAMS) modified high-intensity Cs+ sputter source has several key characteristics, including very high ion current output, that make it useful for AMS applications. Within the AMS community there have been suggestions that certain aspects of operation of a sputter ion source at very high output levels could result in low ionization efficiency and the likelihood of consuming (burning through) small samples without acquiring adequate statistics. This is of particular importance for small mass carbon targets. We have recently re-determined the carbon ionization efficiency of the CAMS sputter source using graphite targets derived from Oxalic Acid I & II and demonstrated relatively high ionization efficiency (∼33%) during the operation of these sources at high output levels. We also examine the relationship between ion source efficiency and sample size.

The anions of the Li, Be and B fluorides: The super-halogens and AMS

During tests with BeF2 samples in a sputter ion source, it was found that the largest negative fluoride ion current was of BeF3-. This is because BeF3 belong to an extensive class of molecules known as super-halogens. These have electron affinities much higher than those of the halogens themselves and so are of great potential interest to AMS. A systematic study of anions of this class for Li, Be and B was therefore undertaken. The strongest fluoride anions measured were LiF2-, BeF3- and BF4- as expected. The anion of LiF3 could not be observed at a ratio of LiF3-/LiF2-∼10-8. The anion of BF3, which is predicted like the anion of BF to be unstable, was observed with intensity modestly greater than that of the BF anion. These measurements illustrate some general properties of super-halogen anions: (1) their great electron binding energies make it possible to produce large currents with Cs+ sputter sources; and (2) the super-halogen anions of the neighbouring elements are often one halogen atom apart, so some degree of isobar selectivity is available at the ion source. The possibility of directly counting 7Be2+ at <2MV terminal voltage, by simply injecting BeF3-, is an example of this realization. Other ramifications of super-halogen anions for low energy AMS development are also discussed.

Toroidally asymmetric distributions of hydrocarbon (CD) emission and chemical sputtering sources in DIII-D

Measurements in DIII-D show that the carbon chemical sputtering sources along the inner divertor and center post are toroidally periodic and highest at the upstream tile edge. Imaging with a tangentially viewing camera and visible spectroscopy were used to monitor the emission from molecular hydrocarbons (CH/CD) at 430.8nm and deuterium neutrals in attached and partially detached divertors of low-confinement mode plasmas. In contrast to the toroidally periodic CD distribution, emission from deuterium neutrals was observed to be toroidally symmetric along the inner strike zone. The toroidal distribution of the measured tile surface temperature in the inner divertor correlates with that of the CD emission, suggesting larger parallel particle and heat fluxes to the upstream tile edge, either due to toroidal tile gaps or height steps between adjacent tiles.

Sputtering source of cluster ions and surface-ionization source of polyatomic ions of organic compounds

Development and characterization of sputtering sources of negative cluster and molecular ions of Aum- (m=1–9), Sim- (m=1–6), SimOn- (m=1–5, n=1–11), Cm- (m=1–12), NimCln- (m=1–2, n=0–3) and surface-ionization (SI) sources of polyatomic positively charged ions of organic compounds are described. The currents of the molecular and cluster ions obtained after separation were very stable and reach several nA for the sputtering source and from 10−10 up to10−7A/sm2 for the SI source. A possibility of using the high selectivity of SI and the high efficiency of SI of nitrogen-containing organic bases to produce practically composition-homogeneous effective beams of polyatomic positively charged ions is demonstrated in this work.

In-situ real time sputtering source health monitoring using ultrasonics

This work describes the technique of monitoring functional health of sputtering source during sputter-deposition process using ultrasound time of flight (TOF) measurements. The TOF is measured between echoes reflecting from boundaries of dissimilar components inside the source. The technique described can be used for in-situ real time monitoring of target thickness, target bond integrity as well as for monitoring of cooling water temperature and target deformation.

Phase tailoring of Ta thin films by highly ionized pulsed magnetron sputtering

Ta thin films were grown on Si substrates at different inclination angles with respect to the sputter source using high power impulse magnetron sputtering (HIPIMS), an ionized physical vapor deposition technique. The ionization allowed for better control of the energy and directionality of the sputtered species, and consequently for improved properties of the deposited films. Depositions were made on Si substrates with the native oxide intact. The structure of the as-deposited films was investigated using X-ray diffraction, while a four-point probe setup was used to measure the resistivity. A substrate bias process-window for growth of bcc-Ta was observed. However, the process-window position changed with changing inclination angles of the substrate. The formation of this low resistivity bcc-phase could be understood in light of the high ion flux from the HIPIMS discharge.

Anisotropic broadening of Cu nanorods during glancing angle deposition

Regular arrays of freestanding Cu nanostructures were grown on patterned Si substrates using glancing angle deposition (GLAD) from two oppositely positioned sputtering sources. Continuous azimuthal substrate rotation during deposition leads to the formation of vertical 430-nm-wide rods, which broaden anisotropically during subsequent growth with a stationary substrate. Statistical analyses of plan-view micrographs combined with numerical simulations indicate a linear increase in the width aspect ratio with deposition time that is attributed to a change in the growth front direction. This technique, termed simultaneous opposite GLAD, provides a unique approach for nanostructure shaping.