Dual Cathode Research Articles

Theoretical analysis of a new extraction system for a DUHOCAMIS operating in a high magnetic field

A new extraction system is designed for a penning ion source DUHOCAMIS (dual hollow cathode ion source for metal ion beams) being installed at the Institute of Heavy Ion Physics, Peking University. We have analyzed theoretically the central particle trajectories in the extraction region for ions having different q/m ratios and then compared our results with the simulation results of CST (Computer Simulation Technology) software. The validity of the system is verified and some analytical formulas are obtained which will be used for the optimization of the extraction system as well as the experimental setup.

Microstructure and temperature coefficient of resistance of thin cermet resistor films deposited from CrSi2–Cr–SiC targets by S-gun magnetron

Technological solutions for producing nanoscale cermet resistor films with sheet resistances above 1000Ω∕◻ and low temperature coefficients of resistance (TCR) have been investigated. 2–40nm thick cermet films were sputter deposited from CrSi2–Cr–SiC targets by a dual cathode dc S-gun magnetron. In addition to studying film resistance versus temperature, the nanofilm structural features and composition were analyzed using scanning electron microscopy, atomic force microscopy, high-resolution transmission electron microscopy, energy-dispersive x-ray spectroscopy, and electron energy loss spectroscopy. This study has revealed that all cermet resistor films deposited at ambient and elevated temperatures were amorphous. The atomic ratio of Si to Cr in these films was about 2 to 1. The film TCR displayed a significant increase when the deposited film thickness was reduced below 2.5nm. An optimized sputter process consisting of wafer degassing, cermet film deposition at elevated temperature with rf substrate bias, and a double annealing in vacuum, consisting of in situ annealing following the film sputtering and an additional annealing following the exposure of the wafers to air, has been found to be very effective for the film thermal stabilization and for fine tuning the film TCR. Cermet films with thicknesses in the range of 2.5–4nm deposited using this technique had sheet resistances ranging from 1800to1200Ω∕◻ and TCR values from −50ppm∕°C to near zero, respectively. A possible mechanism responsible for the high efficiency of annealing the cermet films in vacuum (after preliminary exposure to air), resulting in resistance stabilization and TCR reduction, is also discussed.

Cutting Performance of TiAlSiN Coated Cemented Carbide Tool with Post-Deposition Heat Treatment

In this study, TiAlSiN coatings were synthesized by cathodic arc deposition with Ti and Al88Si12 dual cathodes. The as-deposited coatings were following with post-deposition heat treatment in air and nitrogen atmosphere, respectively, at the temperature of 400 oC for 3 hour. The annealing treatment of the TiAlSiN coating has an expected effect on the wear resistance and cutting performance. The TiAlSiN coating subjected to heat treatment in nitrogen atmosphere presented the best oxidation and wear resistance among the tested coatings. The friction coefficient of the TiAlSiN coatings subjected in nitrogen atmosphere at 400oC was decreased due to the effect of the structure modification by increasing hardness. Using thermogravimetric analyzer (TGA), the result turned out the lowest weight change of TiAlSiN coating after annealing treatment in air if compared to that of all the coatings. The reason my be due to the oxide layer formed on the coating surface acted as a protective layer. Cutting test on the hardened steel with mist oil lubricants, the TiAlSiN-coated WC-Co tool with annealing treatment in nitrogen provides the best wear resistance at the cutting edge.

Design, operation mode, and stress control capability of S-Gun magnetron for ac reactive sputtering

In this paper, the design features, operation modes, and application capabilities of a new generation of the dual cathode S-Gun magnetron for ac (40 kHz) reactive sputtering are discussed. Due to its dual target arrangement and magnetic array configuration, the ac powered S-Gun is uniquely able to realize reactive sputtering processes free of parasitic arcing and disappearing anode effects thus enabling the formation of high quality dielectric films. The L-shaped magnetic array provokes the formation of a wide erosion zone covering the majority of the conical surface of the target. This prevents a build-up of thick dielectric films near the erosion zone allowing reliable arc-less operation of the S-Gun in a poison mode on a back branch of the hysteresis loop. The study has revealed that an effective approach to the process stability control can be based on the simultaneous use of discharge voltage, current, and applied ac power as a combined parameter for stabilization of the process work point. Using the internal shields as subsidiary passive anodes allows redistribution of the discharge current between the targets and the internal shields of the magnetron. A simplified model explaining how the current redistribution influences the substrate temperature and film stress by a controllable suppression of the flux of charged particles to the substrate is discussed. The effectiveness of this technique in stress control is demonstrated in conjunction with deposition of highly textured aluminum nitride films.

Low-temperature deposition of (1 1 0) and (1 0 1) rutile TiO 2 thin films using dual cathode DC unbalanced magnetron sputtering for inducing hydroxyapatite

Thin films of both (1 1 0) and (1 0 1) rutile titanium dioxide (TiO 2) were synthesized using a dual cathode DC unbalanced magnetron sputtering at low temperature with various substrate bias voltages ( V sb) ranging between 0 and −150 V. The TiO 2 film prepared with V sb = 0 underwent heat treatment after deposition. It was observed that the (1 1 0) rutile phase was deposited on the film with V sb below −50 V. Furthermore, the film showed high crystallinity after the heat treatment. However, when using V sb above −50 V, the phase of film shifted to (1 0 1) due to the formation of high-energy particles on the surface. For in vitro testing, the samples were immersed in simulated body fluid (SBF) for 7 days. The heat-treated (1 1 0) rutile shows a poor distribution of hydroxyapatite (HA) formation, generally causing the stress effect. The film was prepared with V sb = 50 V and observed to form higher crystallinity of HA.

Innovative technique for tailoring intrinsic stress in reactively sputtered piezoelectric aluminum nitride films

Novel technical and technological solutions enabling effective stress control in highly textured polycrystalline aluminum nitride (AlN) thin films deposited with ac (40kHz) reactive sputtering processes are discussed. Residual stress in the AlN films deposited by a dual cathode S-Gun magnetron is well controlled by varying Ar gas pressure, however, since deposition rate and film thickness uniformity depend on gas pressure too, an independent stress control technique has been developed. The technique is based on regulation of the flux of the charged particles from ac plasma discharge to the substrate. In the ac powered S-Gun, a special stress adjustment unit (SAU) is employed for reducing compressive stress in the film by means of redistribution of discharge current between electrodes of the S-Gun leading to controllable suppression of bombardment of the growing film. This technique is complementary to AlN deposition with rf substrate bias which increases ion bombardment and shifts stress in the compressive direction, if required. Using SAU and rf bias functions ensures tailoring intrinsic stress in piezoelectric AlN films for a particular application from high compressive −700MPa to high tensile +300MPa and allows the gas pressure to be adjusted independently to fine control the film uniformity. The AlN films deposited on Si substrates and Mo electrodes have strong (002) texture with full width at half maximum ranging from 2° for 200nm to 1° for 2000nm thick films.

Effects of O and N impurities on the nanostructural evolution during growth of Cr/Sc multilayers

Transition metal multilayers are prime candidates for high reflectivity soft x-ray multilayer mirrors. In particular, Cr/Sc multilayers in the amorphous state have proven to give the highest reflectivity in the water window. We have investigated the influence of impurities N and O as residual gas elements on the growth, structure, and optical performance of Cr/Sc multilayers deposited in high vacuum conditions by a dual cathode direct current magnetron sputter deposition. Multilayer structures with the modulation periods in the range of 0.9–4.5 nm and Cr layer to bilayer thickness ratios in the range of 0.17–0.83 were deposited with an intentionally raised base pressure (pB), ranging from 2 × 10−7 to 2 × 10−5 Torr. Compositional depth profiles were obtained by elastic recoil detection analysis and Rutherford backscattering spectroscopy, while the structural investigations of the multilayers were carried out using hard x-ray reflectivity and transmission electron microscopy. By investigating stacked multilayers, i.e., several multilayers with different designs of the modulation periods, stacked on top of each other in the samples, we have been able to conclude that both N and O are incorporated preferentially in the interior of the Sc layers. At pB ≤ 2 × 10−6 Torr, typically <3 at.% of N and <1.5 at.% of O was found, which did not influence the amorphous nanostructure of the layers. Multilayers deposited with a high pB ∼2 × 10−5 Torr, a N content as high as ∼37 at.% was measured by elastic recoil detection analysis. These multilayers mainly consist of understoichiometric face-centered cubic CrNx/ScNy nanocrystalline layers, which could be grown as thin at 0.3 nm and is explained by a stabilizing effect on the ScNy layers during growth. It is also shown that by adding a background pressure of as little as 5 × 10−6 Torr of pure N2 the soft x-ray reflectivity (λ = 3.11 nm) can be enhanced by more than 100% by N incorporation into the multilayer structures, whereas pure O2 at the same background pressure had no effect.

Compositional influence of LSM-YSZ composite cathodes on improved performance and durability of solid oxide fuel cells

The use of a dual-composite approach, in which both LSM and YSZ nanoparticles are placed on YSZ core particles, allows for the development of an ideal cathode microstructure with improved phase contiguity and durability for use in solid oxide fuel cells. The volume fraction of the conjugated YSZ phase plays a critical role in the optimization of the cathode microstructure for achieving good durability because it acts as an interconnecting bridge between YSZ core particles. However, the presence of excess conjugated YSZ phase interrupts the formation of sufficient triple phase boundary sites by disturbing the contacts between the LSM and YSZ phases. Impedance spectroscopy analysis and microstructural observations provide a better understanding of the influence of the composition on the electrochemical performance and durability of these dual composite cathodes.

Factors affecting the performance of microbial fuel cells for sulfur pollutants removal

A microbial fuel cell (MFC) has been developed for removal of sulfur-based pollutants and can be used for simultaneous wastewater treatment and electricity generation. This fuel cell uses an activated carbon cloth+carbon fibre veil composite anode, air-breathing dual cathodes and the sulfate-reducing species Desulfovibrio desulfuricans. 1.16gdm−3 sulfite and 0.97gdm−3 thiosulfate were removed from the wastewater at 22°C, representing sulfite and thiosulfate removal conversions of 91% and 86%, respectively. The anode potential was controlled by the concentration of sulfide in the compartment. The performance of the cathode assembly was affected by the concentration of protons in the cation-exchanging ionomer with which the electrocatalyst is co-bound at the three-phase (air, catalyst and support) boundary.

Dual active material composite cathode structures for Li-ion batteries

The efficacy of composite Li-ion battery cathodes made by mixing active materials that possessed either high-rate capability or high specific energy was examined. The cathode structures studied contained carbon-coated LiFePO 4 and either Li[Li 0.17Mn 0.58Ni 0.25]O 2 or LiCoO 2. These active materials were arranged using three different electrode geometries: fully intermixed, fully separated, or layered. Discharge rate studies, cycle-life evaluation, and electrochemical impedance spectroscopy studies were conducted using coin cell test structures containing Li-metal anodes. Results indicated that electrode configuration was correlated to rate capability and degree of polarization if there was a large differential between the rate capabilities of the two active material species.

Performance enhancement of single-layer miniature cBN wheels using CFUBMS-deposited TiN coating

This work investigated the effectiveness of TiN coating in enhancing the performance of two different types of single-layer cBN grinding wheels. One was galvanically bonded type where galvanic metal layer covered less than 50% of the grit height. In this paper, it is termed as underplated wheel. The other one was brazed cBN wheel which was developed in-house. In this case, the grits were bonded by a braze alloy layer. TiN coating, well known for its anti-wear and anti-friction characteristics, finds use in cutting tools and tribological applications. In this case study, such TiN was successfully deposited on the above-mentioned two types of grinding wheels with a dual cathode closed-field unbalanced magnetron sputtering (CFUBMS) system. Performance of those TiN-coated wheels was compared with that of uncoated counterparts in terms of grinding force and percentage of grit failure. Grinding tests were carried out in plunge mode and under dry condition. Experimental results clearly revealed the fact that the role of TiN coating was not that significant in reducing the friction at the wheel-workpiece contact zone. However, it was able to substantially reduce grit pullout of the underplated cBN wheel. On the other hand, uncoated brazed cBN wheel did not suffer from grit pullout, but severe premature breakage of cBN grits at the bond level was observed. This was remarkably arrested when TiN coating was applied on the active surface of the wheel.

Dual DC magnetron cathode co-deposition of (Al,Ti) and (Al,Ti,N) thin films with controlled depth composition

In this work (Al,Ti) and (Al,Ti,N) films with composition gradient in depth starting either with pure Al or pure Ti were deposited on Si, glass and Au at room temperature in a DC magnetron discharge without bias. The plasma parameters, for both custom made cathodes, were determined and the process was real-time controlled to obtain in the plasma the necessary deposition changes in relative metal abundances to get the desired depth profile composition on the films. In this work the process was designed to get a constant gradient for the composition depth profile. The morphology of the films was analysed by SEM while the composition gradients were measured by SIMS, XPS and RBS, confirming preset nominal depth composition profile of the films. To obtain (Al,Ti,N) thin films with gradient depth composition, N 2 must be supplied to the discharges. The plasma behaviour is modified in the presence of N 2 and the influence on the film characteristics is studied using the same techniques referred above. The (Al,Ti) and (Al,Ti,N) film properties are compared. We succeed in validating the coating technique opening new application possibilities.

Theoretical Investigation Into Longitudinal Cathodal Field Steering in Spinal Cord Stimulation

Objective. When using spinal cord stimulation (SCS) for chronic pain management, precise longitudinal positioning of the cathode is crucial to generate an electrical field capable of targeting the neural elements involved in pain relief. Presently used methods have a poor spatial resolution and lack postoperative flexibility needed for fine tuning and reprogramming the stimulation field after lead displacement or changes in pain pattern. We describe in this article a new method, "electrical field steering," to control paresthesia in SCS. The method takes advantage of newer stimulator design and a programming technique allowing for "continuous" adjustment of contact combination while controlling stimulation current for each contact separately. Method. Using computer modeling we examined how stimulation of dorsal column (DC) and dorsal root (DR) fibers was influenced by changing the current ratio of the cathodes of a dual (--) and a guarded dual cathode (+--+) configuration programmed on a percutaneous lead with 9 and 4mm center-to-center contact spacing. Results. A cathodal current ratio could be found for which DC or DR fiber recruitment and thus, most likely, paresthesia coverage was maximized. The DR threshold profiles shifted longitudinally, thus following the shift in the electrical field during steering. The profiles had a constant shape when the contact spacing was small and a varying shape for wider contact separation. Generally, the wider contact separation provided less DC and more DR fiber recruitment. Conclusions. By means of cathodal steering on a longitudinal contact array, the group of excited DC and DR fibers, and thus paresthesia coverage, can be controlled when using SCS. With widely spaced contacts, superposition of the electrical field from each steering contact is limited. To precisely control segmental paresthesia (DR stimulation), a small contact spacing is necessary.

Effects of layer patterns on magnetic and other properties of single and multilayered Fe–C films

The structure and magnetic properties of Fe–C films synthesized using dual cathodes and coaxial cathodes in a filtered high current pulsed cathodic vacuum arc were studied. By altering the experimental parameters such as the trigger sequence, period, and pulse length, a series of single and multilayered Fe–C films were deposited. X-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy were utilized to study the composition and microstructure of the films. The magnetic properties were studied using a superconducting quantum interference device magnetometer. The hysteresis loops show that the magnetic properties are controlled by the pattern of the layers and Fe concentration in the films. The reduction in the coercive field when Fe layers are mixed with ta-C layers is a key result and confirms that magnetically soft materials can be created by the multilayer method. The relationship between the magnetic properties and the structure of single and multilayered Fe–C films is discussed.

Optical and crystallographic analysis of thin films of GeC deposited using a unique hollow cathode sputtering technique

Experimental results on thin films of the new material Ge x C 1− x , deposited by a unique dual plasma hollow cathode sputtering technique, are presented. The GeC films, grown on etched Si(1 0 0), exhibited remarkable crystallinity with a lattice spacing which has shifted from that of pure Ge toward that of Si. This order has been characterized using X-ray diffraction (XRD) and Raman spectroscopy. The substrate temperature, which yielded the best results to date, was 350 °C. The deposition rate of the Ge and the deposition rate ratio of Ge to C did not have a great effect on the crystallinity. However, the substrate type had a great influence as did the presence of Al as an added impurity. Thin films were grown on etched Si, naturally oxidized Si, and onto glass substrates. The absorption coefficient was much higher for GeC than either Si or Ge. To verify that absorption was greater than Si or Ge for the more crystalline form of GeC, ellipsometry measurements were made. The photon absorption inferred from these ellipsometry measurements confirmed the fact that GeC has a quantum efficiency much greater than crystalline Si or Ge and even more than amorphous Si.

Thin films of GeC deposited using a unique hollow cathode sputtering technique

Experimental results on thin films of the new material Ge x C 1− x , deposited by a unique dual plasma hollow cathode sputtering technique are presented here. The (Ge, C) system is extremely promising since the addition of C to Ge has reduced the lattice dimensions enough to allow a lattice match to silicon, while increasing the bandgap close to that of c-Si. The most important contribution of this work shows that by the non-equilibrium growth conditions present using the hollow cathode technique, one can grow Group IV materials which cannot otherwise be grown using normal CVD or MBE processes. The sputtering is accomplished by igniting a DC plasma of the Ar and H 2 gases which are fed through Ge and C nozzles, cylindrical tubes 30 mm in length with an 8 mm OD and a 3 mm ID.

Lowering the ignition voltage by the dual microhollow cathode configuration for multichannel flat panel lamp

We have developed a dual microhollow cathode configuration, employing one power supply circuit with a resistor that is suitable for lamp starting without additional power supplier. We also investigated their electrical characteristics and photo images, varying the applied voltage. The electrical and optical measurements showed that the discharge passed through four distinct stages: no discharges, the first microhollow cathode discharges, the both of the first and second microhollow cathode discharges, and finally the main discharge. As a result, the Vs and Es∕p of a dual microhollow configuration were lower by a factor of about 2 than those of a diode at 40Torr. We have also observed that the parallel operation can be possible with a single resistor in nine channels flat panel lamp.

Thin Films of GeC Deposited Using a Unique Hollow Cathode Sputtering Technique

AbstractExperimental results on thin films of the new material GexC1-x, deposited by a unique dual plasma hollow cathode sputtering technique are presented here. The (Ge, C) system is extremely promising since the addition of C to Ge has reduced the lattice dimensions enough to allow a lattice match to silicon, while increasing the bandgap close to that of c-Si. The sputtering is accomplished by igniting a dc plasma of the Ar and H2 gases which are fed through Ge and C nozzles, cylindrical tubes 30 mm in length with an 8 mm O.D. and a 3 mm I.D.The basic material, optical, and structural properties were analyzed. Film characterization was performed using Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Auger electron spectroscopy. Additional measurements such as Tauc bandgap, conductivity as a function of temperature and light intensity, and film uniformity have been made. The film properties from a variety of deposition conditions are discussed. The measurements made indicate that the films can be grown so that the C enters the material at lattice sites. In addition, the GexC1-x films absorb photons much more efficiently than either c-Si or c-Ge.Initial results on Al doped films are presented.

P-239L: Late-News Poster: E-2D Advanced Hawkeye: Primary Flight Display

This paper is a response to the challenge of providing a large area avionics display for the E-2D AHE aircraft. The resulting display design provides a pilot with high-resolution visual information content covering an image area of almost three square feet (Active Area of Samsung display = 33.792cm × 27.0336 cm = 13.304″ × 10.643″ = 141.596 square inches = 0.983 sq. ft × 3 = 2.95 sq. ft). The avionics display application, design and performance being described is the Primary Flight Display for the E-2D Advanced Hawkeye aircraft. This cockpit display has a screen diagonal size of 17 inches. Three displays, with minimum bezel width, just fit within the available instrument panel area. The significant design constraints of supporting an upgrade installation have been addressed. These constraints include a display image size that is larger than the mounting opening in the instrument panel. This, therefore, requires that the Electromagnetic Interference (EMI) window, LCD panel and backlight all fit within the limited available bezel depth. High brightness and a wide dimming range are supported with a dual mode Cold Cathode Fluorescent Tube (CCFT) and LED backlight. Packaging constraints dictated the use of multiple U shaped fluorescent lamps in a direct view backlight design for a maximum display brightness of 300 foot-Lamberts. The low intensity backlight levels are provided by remote LEDs coupled through a fiber optic mesh. This architecture generates luminous uniformity within a minimum backlight depth. Cross-cockpit viewing is supported with ultra-wide field-of-view performance including contrast and the color stability of an advanced LCD cell design supports. Display system design tradeoffs directed a priority to high optical efficiency for minimum power and weight.

Structural and mechanical properties of multilayered gradient CrN/ZrN coatings

Multilayered gradient CrN/ZrN coatings were synthesized by a dual cathode dc magnetron sputtering. The influence of species of reaction gases and partial pressures on structural and mechanical properties was explored. Both nanoindentation and nanoscratch fracture tests showed that multilayered gradient coatings possessed much higher hardness and fracture resistance than monolithic ZrN and CrN coatings. A proper percent of NH 3 in N 2 reaction gas was proved to be of benefit to the synthesis of high hardness and fracture-resistant CrN/ZrN coatings with strong adhesion to substrate. The hardness and critical fracture load exceed 55 GPa and 100 mN, respectively. The multilayered gradient structure with strongly mixed CrN(111), Cr 2N(112), ZrN(111), and ZrN(220) orientations is responsible for the enhanced mechanical properties.