Kinetics of the pulsed erosion deposition process induced by high intensity plasma beams

Intense pulsed ion and/or plasma beams can modify the surface properties of materials by melting their near surface region and doping and/or coating w ith foreign atoms reaching doses in the order of 10(17) cm(-2) in a single pulse. Such processes can be performed using a Rod Plasma Injector (RPI), w here plasma pulses are generated as a result of a low-pressure, high curren t discharge between two concentric, cylindrical sets of rod-type electrodes . The discharge is initiated by a HV pulse applied with a delay time tau(d) after the moment of injection of working gas into the inter-electrode spac e. Depending on tau(d), two modes of operation are possible. If 7, is suffi ciently long, the plasma contains almost exclusively the elements of the wo rking gas (PID mode). For short tau(d) in addition to the generation of pla sma of the working gas rapid erosion of the metallic electrodes also occurs (DPE mode). This metal is deposited and in some cases mixed into the subst rate. The aim of the present work was to get insight into the kinetics of t he DPE process. Several experiments with different working gases (N, Ar, an d Xe), different electrode materials (Ti, W) and substrates (Al2O3, Cu) wer e performed. Energy density was approximately 5-7 J/cm(2) and pulse duratio n was approximately 1 mu s, respectively. The two main conclusions have bee n derived. (a) Metal atoms eroded from electrodes do not undergo ionization and acceleration during the discharge (as it is the case with the working gas). Vapor and low energy ions reach the surface when it is already solidi fied after being melted first by the working gas plasma. The metallic coati ng is molten and mixed into the substrate during the subsequent pulse. (b) Erosion of electrodes is caused by some thermal effects as a result of heat ing by ions and electrons - but not by sputtering. (C) 2000 Published by El sevier Science S.A. All rights reserved.