J.O. Rossi

Surface improvements of industrial components treated by plasma immersion ion implantation (PIII): results and prospects

Abstract The major drive for PIII research in recent years has been the widespread use of plasma-based ion implantation in industries aiming at attaining high value-added components. After achieving the domain of the complete basic PIII cycle, we started to pursue the implementation of this process in various types of industrial components. A DC glow discharge source with a controlled plasma floating potential was used in a 100-l PIII system driven by a 30-kV peak voltage, 50 μs duration, up to 1.1 kHz pulse power source, in order to process the components which were provided by regional companies, spanning from machinery tools to prosthesis. The industrial components were set-up in the PIII chamber as received from the companies, after a simple cleaning procedure. In this phase, only nitrogen implantation was performed. The required processing times were typically from 60 to 120 min and the components were treated either individually or in batches. Fast steel drill bits, knife blades for wood cutting, tools for odontological applications, molds made of fast steel, a prosthesis made of Ti alloy, etc., have been three-dimensionally implanted successfully. Next, improvements in the PIII ongoing system included: a 10-kW pulser with up to 60 kV capability, turbo-pump, refrigerated walls, auxiliary heating of the components, a larger chamber and a magnetron sputtering source for hybrid treatments.

Circuit Modeling of Nonlinear Lumped Element Transmission Lines Including Hybrid Lines

A nonlinear lumped element transmission line (NLETL) that consists of an LC-ladder network can be used to convert a rectangular input pump pulse into a series of RF oscillations at the output. The discreteness of the LC sections in the network contributes to the line dispersion while the nonlinearity of the LC elements produces the nonlinear characteristics of the line. Both of these properties combine to produce wave trains of high frequency. This paper describes an NLETL circuit model that is used to simulate RF generation for a given input pump pulse and the experiments used to validate the simulated results. The circuit model is used to study a nonlinear capacitive line that comprises nonlinear C but linear L and a nonlinear inductive line that comprises nonlinear L but linear C. Extensive and comprehensive parametric studies were carried out for the various NLETLs to understand the behavior and characteristics of these lines. Interesting observations were made, and explanations were given for their occurrence. A hybrid line that comprises both nonlinear elements L and C was also investigated using the circuit model with the goal of better matching to a resistive load. Simulations of the hybrid line indicate promising results.

Advances in High-Voltage Modulators for Applications in Pulsed Power and Plasma-Based Ion Implantation

Modern pulsed power technology has its roots in the late 1950s and early 1960s, and it was driven overwhelmingly by applications in national defense carried out by several countries, especially the U.S., U.K., Russia, and China. The following decades, particularly the early 1990s, witnessed an increased interest in compact systems with pulse repetition rate that could be used in nondefense applications such as treatment of material surfaces by plasma and beam interactions, treatment of pollutants, food sterilization, medical applications, etc. This spawned a new generation of pulsed power components (solid-state switches) that led to completely solid-state modulators. This paper describes how the pulsed power technology used originally in beam sources and cathodic arcs has converged to produce power sources for plasma-based ion implantation (PBII) and related technologies. The present state of the art is reviewed, and prospects for future advances are described, especially for PBII.

Plasma immersion ion implantation experiments at the Instituto Nacional de Pesquisas Espaciais (INPE), Brazil

Abstract Historical perspective of the development of PIII devices at the Instituto Nacional de Pesquisas Espaciais (INPE) is given, together with the description of the present system under operation and our overall results on this three-dimensional implantation research. Starting with an ignitron switched pulser (1 pulse per 3 min) and an intermittent microwave plasma, we improved our PIII system developing a pulse forming network (PFN) based pulser (20 Hz), 2 years later. We also improved our plasma source towards a DC, highly stable, medium density glow discharge system. A much faster hard tube pulser was recently incorporated to our PIII system (670 Hz) allowing us to achieve good implantation results in different materials. Presently, we are testing a recently purchased RUP-4 commercial pulser to obtain arc prevented, 1.1 kHz, square pulses for new experiments in this active field of PIII research.

Study of hybrid nonlinear transmission lines for high power RF generation

In recent years there has been great interest in the study of nonlinear lumped element transmission lines for applications in high power RF generation. The line lumped elements account for the line dispersion while reverse varactor diodes or saturated inductors (used as nonlinear elements C & L, respectively) are responsible for the nonlinearity characteristics of the line. Both properties of the line (dispersion & nonlinearity) acting together allow the appearing of high frequency oscillations along the line and at its output, which can be used to feed a load antenna for RF generation. In view of that, there is a great prospect for building a very compact RF generator that can be applied in mobile platforms of defense systems or in satellite communications if the output oscillation frequency obtained is in excess of 1 GHz. Therefore, in this paper we will show through Spice simulations that in principle it would be possible to reach up to this frequency order by means of a hybrid line (i.e. using variable Ls and Cs at the same time).

A 4-kV/2-A/5-kHz Compact Modulator for Nitrogen Plasma Ion Implantation

To treat stainless-steel surfaces by nitrogen plasma implantation, a solid-state compact modulator was devised, in which a 8.0-muF capacitor discharges through a forward converter composed of a low-blocking-voltage insulated-gate-bipolar-transistor switch (1.0 kV) and three step-up pulse transformers, rather than employing hard-tube devices such as in conventional plasma ion implantation pulsers, which are expensive and cumbersome. For this, a modulator was built to produce pulses with amplitudes of the order of 4 kV, duration of about 5.0 mus, and rise time of ~1.0 mus with maximum current/frequencies capabilities of 2.0 A and 5 kHz, respectively

Soliton Generation Using Nonlinear Transmission Lines

In recent years, there has been great interest in the study of nonlinear transmission lines (NLTLs) for high-power radio frequency (RF) generation. The periodicity of the NLTL accounts for dispersion effects, whereas its nonlinear elements (inductors and/or capacitors) are responsible for the nonlinear processes. Both of these mechanisms acting simultaneously on a propagating pulse allow the generation of high-frequency oscillations at the output. The objective of this paper is to study the quantifiable characteristics of these lines for RF generation by means of SPICE circuit simulation and on basis of experiments. The RF generation at 40 MHz is demonstrated through measurement of the fast Fourier transform of the RF signal extracted at the load and by comparison with the corresponding simulated spectrum. It is expected that the technique presented here can be useful for the design of NLTLs to drive compact RF antennas for space applications and defense mobile platforms.

Magnesium plasma immersion ion implantation in a large straight magnetic duct

Magnesium ions were implanted on silicon wafers using a vacuum arc plasma system with a straight 1 m long magnetic duct, 0.22 m in diameter. Good macroparticle filtering was obtained in samples positioned facing the plasma stream and complete filtering was achieved in samples with surfaces parallel to the plasma stream and magnetic field. Deposition is also minimized by placing sample surfaces parallel to the plasma stream. High resolution x-ray diffraction rocking curves of implanted samples show that the changes in lattice constant are due to compressive strain, and the distortion is larger for higher voltages. Without magnetic field the implantation was a few hundred angstroms deep, as expected, but with magnetic field the depth profile was surprisingly extended to over 0.1 μm, a fact for which we do not yet have a convincing explanation, but could be related to radiation enhanced segregation. The presence of a magnetic field increases substantially the retained implantation dose due to the increase in plasma density by two orders of magnitude.

Design of a 150 kV 300 A 100 Hz Blumlein coaxial pulser for long-pulse operation

Blumlein pulse generators have been used with great success for high voltage pulse generation. They are capable of producing pulses in the nanosecond or microsecond ranges depending on the transmission line length and on the topology used. The main problem with this type of generators relates to the presence of stray lines that degrade the overall gain of the device. In this paper, we are proposing a design method of a 150 kV/300 A coaxial Blumlein pulser with pulse duration of 1 /spl mu/s in which the parasitic effects are minimized by winding the transmission lines on coil formers. Also we have developed a model that estimates the pulser voltage gain from just two parameters: the number of stages and the impedance ratio of the transmission line characteristic impedance and the parasitic secondary mode impedance. The model can be applied to other types of Blumlein generators with different geometries such as those made of strip transmission lines.

Modeling of Wound Coaxial Blumlein Pulsers

Blumlein pulsers are well-suited devices for high-voltage pulse generation in nanosecond and microsecond ranges. These generators have been used with great success in several areas such as in breakdown tests, X-ray generation, lasers, and high-energy plasma implantation. They consist of lengths of transmission lines charged in parallel and synchronously discharged in series into the load by using single or multiple switches at the opposite line endings. The main problem with the device performance is the presence of the shield cable impedance contributing to the Blumlein power loss especially when using only one switch. The very well known technique used for minimizing these losses consists of winding the transmission lines to increase the line shielding inductance if coaxial cables are used. Therefore, herein, circuit models are presented to assess theoretically the temporal response of the wound coaxial Blumlein pulsers by using a SPICE circuit simulator. For model assessment, the authors used the experimental results produced by a wound coaxial Blumlein pulser of 100 kV/200 A with 1.0 mus of pulse duration constructed for applications in surface treatment of polymers and aluminum with high-energy ions