R.P. Fetherston

Measurement of electron emission due to energetic ion bombardment in plasma source ion implantation

An experimental procedure has been developed to measure electron emission due to energetic ion bombardment during plasma source ion implantation. Spherical targets (radius=2 cm) of copper, stainless steel, graphite, titanium alloy (Ti‐6Al‐4V) and aluminum alloy (6061) were biased negatively to 20, 30, and 40 kV in argon and nitrogen plasmas. A Langmuir probe was used to detect the propagating sheath edge and a Rogowski transformer was used to measure the current to the target. The measurements of electron emission coefficients compare well with those measured under similar conditions [B. Szapiro and J. J. Rocca, J. Appl. Phys. 65, 3713 (1989)].

Development of an energetic ion assisted mixing and deposition process for TiNx and diamondlike carbon films, using a co-axial geometry in plasma source ion implantation

Plasma source ion implantation (PSII) is a relatively simple technique for the ion implantation/deposition of materials. In PSII a substrate is immersed in a plasma, and high negative voltage pulses are applied to accelerate ions into the substrate resulting in modification of the properties of the material in the near surface region. A technique was developed to produce uniform diamondlike carbon coatings and TiNx films inside and outside a hollow cylinder (substrate). A description of apparatus, experimental methods for this type of deposition process, and preliminary results are presented in this article.Plasma source ion implantation (PSII) is a relatively simple technique for the ion implantation/deposition of materials. In PSII a substrate is immersed in a plasma, and high negative voltage pulses are applied to accelerate ions into the substrate resulting in modification of the properties of the material in the near surface region. A technique was developed to produce uniform diamondlike carbon coatings and TiNx films inside and outside a hollow cylinder (substrate). A description of apparatus, experimental methods for this type of deposition process, and preliminary results are presented in this article.

OVERVIEW OF PLASMA SOURCE ION IMPLANTATION RESEARCH AT UNIVERSITY OF WISCONSIN-MADISON

In the last five years, plasma source ion implantation (PSII) research at the University of Wisconsin–Madison, has encompassed work in the areas of plasma physics, diagnostics, ion‐material interactions’ modeling, materials science issues, and a broad spectrum of industrial applications of PSII technology. The third generation PSII system is presently under construction. Three methods of plasma generation, namely, electron impact method, glow discharge, and radio frequency have been successfully employed. In the following article the highlights of the above facets of PSII research activities have been presented.

An evaluation of metallic coatings for erosive wear resistance in die casting applications

An accelerated testing procedure with a multi-pin die has been established for the study of the erosive wear of die materials and surface treatments in die casting applications, under production conditions. This test procedure utilizes the wear of core pins as a surrogate measure of die erosive wear, and is used to evaluate the efficacy of coatings and die surface treatments in reducing erosive wear in dies under actual production conditions. Metallic coatings of W, Mo, and Pt deposited on the test pins using the plasma source ion implantation technique (PSII) technology in the ion assisted deposition mode, were then evaluated for erosion resistance using this developed test procedure. The results of this evaluation on the effectiveness of these metallic coatings are presented here along with possible reasons for such coating behavior.

Measurement of ion species ratio in the plasma source ion implantation process

Ion species and their ratios in nitrogen, oxygen, and argon plasmas in the plasma source ion implantation process have been determined with a simple and low‐cost measurement system. The measured ion species ratio in the nitrogen plasma was used as an input parameter for the computer simulation code transport and mixing from ion irradiation to predict the atomic composition‐depth profile. Comparison between the code results and data derived from Auger analysis for a nitrogen‐implanted Ti‐6Al‐4V alloy showed good agreement. In this article, the design, performance, and possible future improvements regarding the resolution of this measurement system will be discussed.

Sheath dynamics and dose analysis for planar targets in plasma source ion implantation

A comparison of the experimental measurements and numerical calculations of temporal and spatial sheath evolution for planar targets is presented. The propagating sheath edge initially emanates in an ellipsoidal shape elongated along the plane of the target, then transforms to a spherical shape at a distance of about one diameter from the target, and ultimately the sheath becomes stationary at a distance that depends on the plasma parameters and target dimensions. To complement sheath expansion measurements with dose uniformity in planar targets, silicon wafers were implanted with nitrogen. Surface profilometry and scanning Auger microprobe measurements showed greater sputtering and shallower implantation depths at the edge of the wafer, relative to the centre, in qualitative agreement with the sheath expansion measurements.

Distribution of incident ions and retained dose analysis for a wedge‐shaped target in plasma source ion implantation

A wedge‐shaped target was implanted with nitrogen ions using the plasma source ion implantation process, in order to understand the effects of the target edges on the energy and fluence distribution of incident ions. Experimental measurements and analysis of retained dose on silicon samples affixed on the surface of the target, showed results consistent with those predicted by theoretical models. Higher retained dose and greater implantation depths were observed in the vicinity of the edge contained by the normal angle as compared to the edges contained by the acute angles. The target face with smaller area accumulated, on the average, higher dose compared to the face with the larger area.

Surface modification of Ti6Al4V surgical alloy by plasma source ion implantation

Abstract Plasma source ion implantation (PSII) was applied to Ti6Al4V surgical alloy to improve its tribological properties. Nitrogen implantation at room temperature produced an improvement in wear resistance. Implantation at an elevated temperature (approximately 600 °C) resulted in a substantially thicker modified surface layer with sustained wear resistance. The best results were obtained by a two-step process wherein elevated temperature implantation was followed by room temperature implantation. The tribological properties resulting from this two-step process surpassed those of the CoCr alloy and were comparable with those obtained by ion nitriding. The base material properties remained unchanged after the PSII treatments. The surface properties were characterized using low-road microhardness measurements, pin-on-disk wear testing and Auger spectroscopy.

Sputter deposition of tantalum-nitride films on copper using an RF-plasma

A tantalum-nitride film was successfully deposited at ambient temperature on copper with a modified ion-assisted-deposition (IAD) technique. The process uses an argon and nitrogen plasma to sputter deposit from a tantalum rf-cathode and ion implant the deposited film simultaneously. Both argon and nitrogen ions are used for sputtering and ion implantation. Auger spectroscopy and x-ray diffraction were used to characterize the resulting film.

Adaptation of metal arc plasma source to plasma source ion implantation

Summary form only given, as follows. In Plasma Source Ion Implantation (PSII) a target is immersed in a plasma and a train of high negative voltage pulses is applied to accelerate ions into the target and to modify the properties in the near surface region. In PSII, until now we have been using gaseous species to generate plasmas. However metal ion plasma may be used to modify the surface properties of material for industrial applications. Conventionally the ion implantation of metal ions is performed using beam line accelerators which have complex engineering and high cost. The employment of a metal are source to PSII has tremendous potential due to its ability to process the conformal surfaces, simple engineering and cost effectiveness. We have installed metal arc source for generation of titanium plasma. Currently, we investigating the properties of titanium plasma material behavior of titanium implanted aluminum and 52100 steel. The recent results of this investigation are presented.