| Boring, K. L. and Stauffer, L. H. |
| A new non-thermionic electron gun. |
| Proceedings of the National Electronics Conference v.19, pp.535-544. (1963). |
| Abstract: Recenct advances in the design of electron guns utilizing cold hollow cathodes are described. Controlled electron beams having energies up to 100 kV have been generated in Argon at pressures from 2 to 10 microns. Beam intensities of 2 amperes have been obtained with energies up to 20 kV. By means of an auxiliary electromagnetic focusing lens, focal spot sizes approximately .01 inch in diameter have been formed for welding experiments.
Since the beam intensity increases with cathode potential and with gas pressure, these variables are independently controlled. Continuous control of beam intensity, at any desired cathode potential, is accomplished, by varying the potential of the internal electrode. Internal controal electrodes of several types are described and the control characteristics are shown.
Electric field configuration at the exit aperture of the cathode plays an important role in the stability and degree of collimation of the beam. This is shown to be a function of gun geometry and density of ionization. A cathode design is described which has stable operating characteristics over a wide range of accelerating voltage. Volt-ampere characteristics of the electron beam are given as a function of control electrode potential.
Experimental applications to materials joining and vacuum metallurgy are desribed. |
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| Fu, R. K. Y., Chu, P. K., and Tian, X. B. |
| Influence of thickness and dielectric properties on implantation efficacy in plasma immersion ion implantation of insulators. |
| Journal of Applied Physics v.95, n.7, pp.3319-3323. (2004). |
| Abstract: Plasma immersion ion implantation of insulators is an interesting topic both theoretically and industrially. The net energy of the incident ions is dictated by the surface potential and for conductors is equal to the voltage applied to the backside or sample stage. However, the poor electrical conductivity of insulating materials can lead not only to charging during ion bombardment but also reduced surface potential due to the capacitance effect. In the work described in this paper, we theoretically and experimentally investigate the influence of the thickness and dielectric properties of insulating materials on the implantation efficacy. The use of mesh-assisted PIII by covering the insulating materials with an electrically conducting cage to enhance the implantation efficacy is also compared experimentally. Our theoretical results suggest that a low plasma density induces less surface charges and higher surface potential. Our experimental data show good agreement with the theoretical results and mesh-assisted PIII does yield net improvement. (C) 2004 American Institute of Physics |
| Online at: Link to Online Reference
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| Fu, R. K. Y., Fu, K. L., Tian, X. B., and Chu, P. K. |
| Effects of mesh-assisted carbon plasma immersion ion implantation on the surface properties of insulating silicon carbide ceramics. |
| Journal of Vacuum Science & Technology, A: Vacuum, Surfaces, and Films v.22, n.2, pp.356-360. (2004). |
| Abstract: Plasma immersion ion implantation (PIII) is an effective materials modification and synthesis technique but has seldom been applied to ceramic materials due to the high electrical resistance that reduces the ion bombardment energy and sometimes causes serious electrical arcing in the instrument. Even in cases where PIII is applicable, the surface properties of the implanted insulating materials can be seriously affected due to the low ion energy and materials damage from electrical arcing. In order to enhance the surface and mechanical properties such as wear resistance of ceramic materials used in many industrial applications, surface modification is needed. In this work, we conduct carbon implantation into sintered alpha-SiC (silicon carbides that are widely used in vacuum ceramic bearings) using mesh-assisted plasma immersion ion implantation to enhance the surface properties. The use of a conducting grid is necessitated by the high electrical resistance that induces a large voltage drop across the substrate when a negative voltage is applied to the back of the specimen. The rough surfaces make direct assessment of the shallow depth profiles difficult and so we directly measure the hardness and surface friction coefficients, both of which are significantly enhanced after implantation. Our data suggest different wear mechanisms for the unimplanted and implanted samples as inferred from the surface topography and wear tracks. (C) 2004 American Vacuum Society |
| Online at: Link to Online Reference
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| Fu, R. K. Y., Tian, X., and Chu, P. K. |
| Enhancement of implantation energy using a conducting grid in plasma immersion ion implantation of dielectric/polymeric materials. |
| Review of Scientific Instruments v.74, n.8, pp.3697-3700. (2003). |
| Abstract: Plasma immersion ion implantation (PIII) is conducted on insulating materials using a conducting grid to enhance the ion implantation energy. The biased grid that is connected to the sample holder enshrouds the insulating specimens, and ions from the overlying plasma are implanted through the grid into the samples. The implantation voltage is applied to the grid via the sample platen so problems associated with PIII of insulating materials such as capacitance and charging (and secondary electrons) effects can be greatly alleviated. In the work reported here, we investigate the efficacy of the grid approach. Secondary ion mass spectrometry is used to determine the nitrogen depth profiles. Simulation indicates that for insulating specimens that are plasma implanted without the conducting grid, the maximum nitrogen ion energy is only about 23 keV for an applied voltage of 40 kV while it improves to 30 keV in the presence of the grid. The experimental results are consistent with the surface potentials derived from theoretical modeling of the charging effects. To further improve the ion implantation energy, more effective grid dimension scaling and surface shielding, more optimal separation between the conducting grid and insulator surface, as well as better confinement of the secondary electrons are required. (C) 2003 American Institute of Physics |
| Online at: Link to Online Reference
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| Hyuneui, L., Yeonhee, L., Seunghee, H., Youngwoo, K., Jeonghee, C., and Kang-Jin, K. |
| Reduction in surface resistivity of polymers by plasma source ion implantation. |
| Surface and Coatings Technology v.160, n.2-3, pp.158-164. (2002). |
| Abstract: The surface resistivity of several polymers such as poly (styrene/butadiene copolymer), modified poly(phenyleneoxide), poly(ethylene terephthalate), and polyimide was improved by the argon gas plasma source ion implantation (Ar-PSII) technique equipped with a mesh-type conducting grid. With the grid, the surface resistivities of the modified polymers decreased up to 11 orders of magnitudes at a high ion dose, and remained nearly at the same values after 3 months. The PSII treated polymer sample with the grid provided more uniformly modified surface and lower surface resistivity than that treated without the grid. The extent of the decrease in surface resistivity depended on the polymer structures and physical properties. However, the surface resistivity was independent of the sample thickness, the grid size, and the grid height. Surface analyses using scanning electron microscopy, time-of-flight secondary ion mass spectrometry, and Raman spectroscopy provided the useful information on modified surfaces |
| Online at: Link to Online Reference
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| Kim, C. K. and Economou, D. J. |
| Plasma molding over surface topography: Energy and angular distribution of ions extracted out of large holes. |
| Journal of Applied Physics v.91, n.5, pp.2594-2603. (2002). |
| Abstract: Plasma molding over surface topography was investigated by measuring the energy and angular distribution of ions extracted from a hole in contact with a high density plasma. Holes with diameter larger than as well as smaller than the local sheath thickness were studied in argon or deuterium gas. When the hole diameter (10 mum) was much less than the sheath thickness, the plasma was not perturbed by the presence of the hole. The ion energy distribution (IED) had multiple peaks due to ions sampling the time-varying potential while crossing the sheath. The ion angular distribution (IAD) was Gaussian, peaking at zero angle with respect to the surface normal. These results agree with reported studies. At the other extreme, when the hole diameter (1270 mum) was larger than the sheath thickness, plasma "leaked" into the hole. The IED had a single peak since ions now experience an average sheath potential. The IAD was quite broad extending beyond 30degrees off normal. When the hole diameter (508 mum) was comparable to the sheath thickness, the shape of the IED and IAD was in-between the two extremes mentioned above. The IAD became more isotropic with increasing power, suggesting that the plasma leaked only partly through the hole (the plasma-sheath meniscus was located inside the hole). For all cases, increasing pressure resulted in lower ion energy in argon plasmas due to ion-neutral collisions. Increasing pressure had little effect on the ion energy for deuterium plasmas, for hole diameter less than 508 mum. This is due to the smaller ion-neutral collision cross section for deuterium. (C) 2002 American Institute of Physics |
| Online at: Link to Online Reference
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| Kim, D. and Economou, D. J. |
| Plasma molding over surface topography: Simulation of ion flow, and energy and angular distributions over steps in RF high-density plasmas. |
| IEEE Transactions on Plasma Science v.30, n.5, pp.2048-2058. (2002). |
| Abstract: A two-dimensional fluid/Monte Carlo (MC) simulation model was developed to study plasma "molding" over surface topography. The radio frequency (RF) sheath potential evolution, ion density, and flux profiles over the surface were predicted with a self-consistent fluid simulation. The trajectories of ions and energetic neutrals (resulting by ion neutralization on surfaces or charge exchange collisions in the gas phase) were then followed with a MC simulation. In this paper, ion flow, energy and angular distributions of ions, and energetic neutrals bombarding an otherwise planar surface with a step are reported. The step height was comparable to the sheath thickness for the RF high-density plasma considered. As one approaches the step sidewall, the ion flux decreases, the ion energy distribution narrows, and the ion impact angle increases drastically. The ion impact angle at the foot of the step scales with the ratio of sheath thickness to step height. The energetic neutral flux is found to be comparable to the ion flux on the horizontal surface near the step sidewall. Simulation results are in good agreement with experimental data on ion flux and ion energy and angular distributions near the step |
| Online at: Link to Online Reference
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| Kim, D. and Economou, D. J. |
| Plasma molding over deep trenches and the resulting ion and energetic neutral distributions. |
| Journal of Vacuum Science & Technology B v.21, n.4, pp.1248-1253. (2003). |
| Abstract: A two-dimensional fluid/Monte Carlo simulation was developed to study plasma molding over deep trenches and the resulting ion and energetic (fast) neutral distributions, with emphasis on neutral beam sources. Plasma molding occurs when the sheath thickness is comparable to or smaller than the trench width. Using the electric field profiles predicted by the self-consistent fluid simulation, ions and energetic neutrals (resulting mainly by ion neutralization on the sidewall) were followed by the Monte Carlo simulation. The dominant energetic species at the bottom of a high aspect ratio trench were neutrals. A thin sheath (compared to the trench width), favored a larger energetic neutral flux at the bottom, at the expense of neutral energy and directionality. A relatively thick sheath produced neutrals of higher directionality at the expense of neutral flux. Neutral energy and directionality both increased by increasing the sheath potential. (C) 2003 American Vacuum Society |
| Online at: Link to Online Reference
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| Kim, D. and Economou, D. J. |
| Simulation of a two-dimensional sheath over a flat wall with an insulator/conductor interface exposed to a high density plasma. |
| Journal of Applied Physics v.94, n.5, pp.2852-2857. (2003). |
| Abstract: The structure of the two-dimensional (2D) sheath over a flat, electrically inhomogeneous wall exposed to a high density plasma was investigated by a fluid model. The wall consisted of a floating semi-infinite insulator in contact with a semi-infinite conductor biased by a negative dc voltage. The difference in sheath potential over the two materials resulted in a 2D sheath over the insulator/conductor interface. The ion flux was higher on the conductor side of the interface at the expense of the flux on the insulator side. The spatial extend and magnitude of the ion flux disturbance scaled with the difference in the sheath thickness over the two different materials. The ion impact angle along the surface increased progressively as the material interface was approached. Sheath distortion was exacerbated when the electron temperature was decreased or the bias potential was made more negative. (C) 2003 American Institute of Physics |
| Online at: Link to Online Reference
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| Kim, D. and Economou, D. J. |
| Simulation of plasma molding over a ring on a flat surface. |
| Journal of Applied Physics v.94, n.6, pp.3740-3747. (2003). |
| Abstract: A fluid/Monte Carlo simulation model was developed to study plasma molding over an axisymmetric feature (a ring) resting on an otherwise planar surface in contact with a high-density rf plasma. The two-dimensional (rz) time-dependent sheath potential, and ion density and flux profiles were predicted with a self-consistent fluid simulation. The trajectories of ions and energetic neutrals (resulting mainly by ion neutralization on the cylindrical sidewalls of the ring) were then followed with a Monte Carlo simulation, in an effort to obtain their energy and angular distributions on the substrate surface. When the sheath thickness was comparable to the size of the ring, strong radial electric fields deflected oncoming ions toward the sidewalls of the ring. The ion density was lower in the cylindrical well formed by the ring, compared to outside, resulting in a locally thicker sheath and a smaller spread in the double-peaked ion energy distributions at the bottom of the well. The ion impact angle increased progressively as the sidewalls were approached. The angular distribution of energetic (fast) neutrals at the bottom of the well was bimodal. The energy distribution of fast neutrals at the bottom of the well was broader compared to the parent ion energy distributions. (C) 2003 American Institute of Physics |
| Online at: Link to Online Reference
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| Kim, D. and Economou, D. J. |
| Simulation of a two-dimensional sheath over a flat insulator-conductor interface on a radio-frequency biased electrode in a high-density plasma. |
| Journal of Applied Physics v.95, n.7, pp.3311-3318. (2004). |
| Abstract: A combined fluid/Monte Carlo (MC) simulation was developed to study the two-dimensional (2D) sheath over a flat insulator/conductor interface on a radio-frequency (rf) biased electrode in a high-density plasma. The insulator capacitance increased the local impedance between the plasma and the bias voltage source. Thus, for uniform ion density and electron temperature far away from the wall, the sheath potential over the insulator was only a fraction of that over the conductor, resulting in a thinner sheath over the insulator. The fluid model provided the spatiotemporal profiles of the 2D sheath electric field. These were used as input to the MC simulation to compute the ion energy distribution (IED) and ion angular distribution (IAD) at different locations on the surface. The ion flux, IED, and IAD changed drastically across the insulator/conductor interface due to the diverging rf electric field in the distorted sheath. The ion flux was larger on the conductor at the expense of that on the insulator. Both the ion impact angle and angular spread increased progressively as the material interface was approached. The ion impact energy and energy spread were smaller on the insulator as compared to the conductor. For given plasma parameters, as the insulator thickness was increased, the sheath potential and thickness over the insulator decreased, and sheath distortion became more pronounced. (C) 2004 American Institute of Physics |
| Online at: Link to Online Reference
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| Kim, D., Economou, D. J., Woodworth, J. R., Miller, P. A., Shul, R. J., Aragon, B. P., Hamilton, T. W., and Willison, C. G. |
| Plasma molding over surface topography: Simulation and measurement of ion fluxes, energies and angular distributions over trenches in RF high density plasmas. |
| IEEE Transactions on Plasma Science v.31, n.4, pp.691-702. (2003). |
| Abstract: A two-dimensional (2-D) fluid/Monte Carlo (MC) simulation model was developed to study plasma "molding" over a trench. The radio frequency sheath potential evolution and ion density and flux profiles over-the surface were predicted with a self-consistent fluid simulation. The trajectories of ions and energetic neutrals (resulting by ion neutralization on surfaces or charge exchange collisions in the gas phase) were then followed with a MC simulation.. For sheath thickness L-sh comparable to the trench width D, ions were, strongly deflected toward the trench sidewall, and the ion flux along the trench surface contour was highly nonuniform. Irrespective of the trench depth, the normalized spatially-average ion flux at the trench mouth showed a minimum at L-sh/D similar to 1.0. The normalized spatially-average ion flux at the trench bottom decreased with increasing trench depth or aspect ratio) As the trench sidewall was approached, the energy spread DeltaE of the ion energy distributions (IEDs) at the trench bottom decreased for a thin sheath, but increased for a thick sheath. At the trench bottom, the neutral flux was comparable to the ion flux over the entire range of. sheath thickness studied. Simulation results were in good agreement with experimental data on ion flux, IEDs, and ion angular distributions at the trench bottom |
| Online at: Link to Online Reference
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| Kostov, K. G., Barroso, J. J., and Ueda, M. |
| Two Dimensional Computer Simulation of Plasma Immersion Ion Implantation. |
| Brazilian Journal of Physics v.34, n.4B, pp.1689-1695. (2004). |
| Abstract: The biggest advantage of plasma immersion ion implantation (PIII) is the capability of treating objects with irregular geometry without complex manipulation of the target holder. The effectiveness of this approach relies on the uniformity of the incident ion dose. Unfortunately, perfect dose uniformity is usually difficult to achieve when treating samples of complex shape. The problems arise from the non-uniform plasma density and expansion of plasma sheath. A particle-in-cell computer simulation is used to study the time-dependent evolution of the plasma sheath surrounding two-dimensional objects during process of plasma immersion ion implantation. Before starting the implantation phase, steady-state nitrogen plasma is established inside the simulation volume by using ionization of gas precursor with primary electrons. The plasma self-consistently evolves to a non-uniform density distribution, which is used as initial density distribution for the implantation phase. As a result, we can obtain a more realistic description of the plasma sheath expansion and dynamics. Ion current density on the target, average impact energy, and trajectories of the implanted ions were calculated for three geometrical shapes. Large deviations from the uniform dose distribution have been observed for targets with irregular shapes. In addition, effect of secondary electron emission has been included in our simulation and no qualitative modifications to the sheath dynamics have been noticed. However, the energetic secondary electrons change drastically the plasma net balance and also pose significant X-ray hazard. Finally, an axial magnetic field has been added to the calculations and the possibility for magnetic insulation of secondary electrons has
been proven. |
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| Lee, Y. H. and Han, S. H. |
| Method for surface modification of 3-dimensional bulk polymers. |
| v.702612, n.6403167, (2002). |
| Abstract: A method for surface modification of 3-dimensional bulk polymers is provided to improve surface properties and surface conductivity of 3-dimensional bulk polymers by using plasma source ion implantation technique. The plasma source ion implantation technique is to modify the surface by implanting ions into the surface of the 3-dimensional samples uniformly. When negative high voltage pulse is applied to a metallic grid around the bulk polymer samples, ions are extracted from the plasma; most of ions passing the grid and collide with the surface of the bulk polymer samples in high energy. Therefore, through the method for applying high voltage pulse to the grid around samples, ions are implanted into the surface of the 3-dimensional bulk polymer samples uniformly, and thereby the ions implanted in high energy modify the bulk polymer surface to improve the electrical conductivity effectively. |
| Online at: Link to Online Reference
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| Matossian, J. N., Schumacher, R. W., and Pepper, D. M. |
| Surface potential control in plasma processing of materials. |
| v.995864, n.5374456, (1994). |
| Abstract: An object (30) is plasma processed by placing an electrically conducting grid (34) over all or a portion of the surface (32) of the object (30) so that the grid (34) generally follows the contours of the surface (32) but is displaced outwardly from the surface (32). Ions or electrons from a plasma surrounding the object (30) are accelerated into the surface (32) of the object (30) using as a processing driving force an electrical potential applied to the electrically conducting grid (34). The use of a contoured conducting grid (34) allows plasma processing of large, electrically nonconducting objects and objects having sharp surface features or recesses. |
| Online at: Link to Online Reference
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| Powles, R. C., Kwok, D. T. K., McKenzie, D. R., and Bilek, M. M. M. |
| Simulation of a semi-transparent conducting mesh electrode for plasma immersion ion implantation. |
| Physics of Plasmas v.12, n.9, pp.093507 (2005). |
| Abstract: Particle-in-cell (PIC) simulations of plasma evolution in the vicinity of a mesh electrode which is semi-transparent to ions are presented. Space charge accumulation and ion focusing have an important effect on the ion trajectories and ion energy distribution inside the mesh. The results indicate that when such an electrode is used to assist plasma immersion ion implantation of insulating targets, the initial plasma conditions and mesh geometry are key factors in achieving optimum dose uniformity and implanted ion energy. |
| Online at: Link to Online Reference
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| Ryu, J. H., Cho, B. O., Hwang, S. W., Moon, S. H., and Kim, C. K. |
| Trajectories of ions inside a Faraday cage located in a high density plasma etcher. |
| Korean Journal of Chemical Engineering v.20, n.2, pp.407-413. (2003). |
| Abstract: Simulation was used to investigate potential distributions around a grid of a Faraday cage and trajectories of ions inside the cage located in a high density CF4 plasma etcher. It was observed that the potential distributions near the edge of the grid openings (or near the grid wires) were disturbed, due to the partial leakage of the plasma through the grid openings whose size was comparable to the sheath thickness. corresponding trajectories of ions incident through the grid openings near the edge were found to deflect from the surface normal and focus below the grid wires. It is this ion focusing that is responsible for higher etch rates of SiO2 films below the grid wires compared to those below the grid openings at a proper distance between the grid and the substrate surface. When the substrate was located sufficiently far away from the grid plane (8 mm), the ion trajectories overlapped with each other and the etch rates were uniform across the substrate. At the gap of 0.3 mm from the grid plane, however, ion focusing does not play a role due to close proximity to the grid. This resulted in much higher etch rates below the grid openings than those below the grid wires. The etch rates were also measured at various distances between the grid and the substrate surface. The behavior of the simulated distributions of the etch rates showed good agreement with the measured ones |
| Online at: Link to Online Reference
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| Sarkissian, A. H., Bourque-Viens, A., Paynter, R. W., Saint-Jacques, R. G., and Stansfield, B. L. |
| Characterization of diffused ECR plasma-Application to pulsed plasma ion implantation of nitrogen in titanium. |
| Surface and Coatings Technology v.98, n.1-3, pp.1336-1340. (1998). |
| Abstract: A compact surface electron cyclotron resonance (ECR) plasma source, developed at Institut National de la Recherche Scientifique (INRS)-Energie et Materiaux, has been used as a versatile surface treatment tool. The source has been operated with nitrogen for application to plasma assisted nitriding near room temperature. A negatively biased titanium target is immersed in the processing chamber (PC) plasma. The pulsed plasma diffuses from the ECR source across a transparent grid and fills the PC. The ions are accelerated and implanted into the Ti target. The electric field distribution in the PC, and therefore the uniformity of the implantation, was controlled using a highly transparent grounded grid. For a typical operating pressure of about 0.1-0.2 Pa, and with ~ 300 W of microwave power coupled to the plasma source, a flat density profile with ne = 2.5 x 1015 m-3 (over a diameter > 0.07 m) was measured by a scanning Langmuir probe in the PC. The electron temperature was 6.5 eV, and it also had a flat profile. In these preliminary experiments, ion nitriding of titanium samples was achieved with 30 keV nitrogen ion implantation. The hardness of the Ti target surface changed from 3.4 GPa to 5.8 GPa following the implantation. The depth profile of the implanted ions, measured by the X-ray photoelectron spectroscopy technique, combined with the simulation results from the TRIM code suggests that ion-neutral collisions in the PC were not frequent enough to alter the ion energy distribution significantly |
| Online at: Link to Online Reference
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| Schumacher, R. W., Matossian, J. N., and Goebel, D. M. |
| High impedance plasma ion implantation method and apparatus. |
| v.971433, n.5,330,800, (1994). |
| Abstract: A high dose rate, high impedance plasma ion implantation method and apparatus to apply high voltage pulses to a target cathode within an ionization chamber to both sustain a plasma in the gas surrounding the target, and to implant ions from the plasma into the target during at least a portion of each pulse. Operating at voltages in excess of 50 kV that are too high for the reliable formation of a conventional glow discharge, the plasma is instead sustained through a beam-plasma instability interaction between secondary electrons emitted from the target and a background pulsed plasma. The voltage pulses are at least about 50 kV, and preferably 100 kV or more. Pulse durations are preferably less than 8 microseconds, with a frequency in the 50-1,000 Hz range. The preferred gas pressure range is 1.times.10.sup.-4 -1.times.10.sup.-3 Torr; auxiliary electrodes can be used at the lower pressures to provide sufficient seed electrons for initiating a plasma, which is sustained by the beam-plasma instability interaction. |
| Online at: Link to Online Reference
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| Ueda, M., Kostov, K. G., Beloto, A. F., Leite, N. F., and Grigorov, K. G. |
| Surface modification of polyethylene terephthalate by plasma immersion ion implantation. |
| Surface and Coatings Technology v.186, n.1-2, pp.295-298. (2004). |
| Abstract: Plasma immersion ion implantation (PIII) of nitrogen has been successfully employed to form an amorphous carbon layer on the surface of 0.25-mm-thick polyethylene terephthalate (PET) sheet used for manufacturing plastic bottles. A DC glow discharge source with controlled floating plasma potential was used to create nitrogen plasma in a 100-1 PIII system. The polymer specimens were pulsed (through a metallic grid or sample holder) at repetition rate of 300 Hz with high negative voltage pulse of 10 W magnitude and 80 mus duration. Formation of carbon film on the PET surface as a result of nitrogen ion implantation was investigated using Raman spectroscopy, optical and atomic force microscopy (AFM). The obtained Raman spectra reveal that the amorphous carbon layer has diamond-like characteristics. AFM micrographs demonstrate that after PIII treatment, the PET surface became much smoother and no cracks were found on it. (C) 2004 Elsevier B.V. All rights reserved |
| Online at: Link to Online Reference
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| van Passen, H. L. L., Muly, E. C., and Allen, R. J. |
| Electron beam phenomena associated with perforated wall hollow cathode discharges. |
| Proceedings of the National Electronics Conference v.18, pp.590-596. (1962). |
| Abstract: Perforated wall hollow cathode structures operated in reduced pressure gas atmospheres have produced well defined electron beams. Some of the characteristics of these perforated wall hollow cathode discharges are presented.
The effects of cathode geometry, pressure, voltage and other variables on the operating characteristics of the electron beam mode gas discharge are investigated. Electrostatic field shaping techniques used in producing high power operation of the electron beam mode are presented. The production of high power level electron beams in a low pressure gas atmosphere affords an opportunity for experimental studies which is not otherwise readily available. Several interesting effects associated with the electron beam mode have been observed during the experimental work which may suggest applications in various fields of experimental plasma physics. |
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| Zeng, Z., Fu, R. K. Y., Tian, X., and Chu, P. K. |
| Plasma immersion ion implantation of industrial gears. |
| Surface and Coatings Technology v.186, n.1-2, pp.260-264. (2004). |
| Abstract: Plasma immersion ion implantation (PIII) has been shown to be an effective surface treatment technique for industrial components, especially those possessing an irregular shape. Gears are widely used for rotary mechanical motion in various industrial machines. Extensive wear can occur on the surfaces due to mechanical contact but the complex shape renders conventional surface modification difficult. In this work, we investigated argon and nitrogen PIII of industrial gears. Rutherford backscattering spectrometry (RBS) was used to determine the implanted ion dose along the gear surface using silicon samples affixed at different positions. The results show that the lateral difference of implanted ion dose is quite large. We have also found a large iron content on the silicon surface at some positions. This corresponds to the degree of sputtering near this position and also reflects the ion implantation angle. Our results indicate that the ion dose along the tooth flank is less than that in other positions on the gear surface, and sputtering is more serious due to the larger ion incident angle as a result of the sheath propagation |
| Online at: Link to Online Reference
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