TY - BOOK

T1 - Pulsed Cathodic Arcs from Nb-Al Cathodes

AU - Zöhrer, Siegfried

N1 - embargoed until 28-03-2020

PY - 2019

Y1 - 2019

N2 - Cathodic arcs explosively transform the cathode material into a plasma, a phenomenon which is often utilized to deposit thin films, but can also serve as an ion source for other applications. Particularly for cathodic arc deposition, a better understanding of the influence of the cathode material to arc plasma properties is relevant. While extensive experimental data in literature led to a good comprehension of the relationship of single-element cathode materials to their arc plasma properties, effects introduced by multi-element cathode materials are explored less frequently and many open questions remain. For example, it is still unclear if physical concepts like the cohesive energy rule can be applied to multi-element cathodes. Therefore, a Nb-Al cathode model system was used within this work to study the effect of multi-element cathodes on arc properties. It includes pure Nb and Al cathodes, 3 intermetallic cathodes where each one is composed of one of the 3 intermetallic phases in the Nb-Al system, and 3 composite Nb-Al cathodes with atomic ratios corresponding to the stoichiometric ratios of the intermetallic phases. Pulsed cathodic arcs from these cathodes were examined in high time resolution by recording voltage and current of the discharges; by obtaining ion energy and charge state distributions in the arc plasma in high vacuum and Ar atmospheres; and by investigating converted layers of eroded cathodes. The results show that arc plasma properties from Nb-Al cathodes are quite different from the properties of their single-element counterparts and do not follow a simple linear interpolation between them like related cohesive energies. The composite/intermetallic morphology of bulk cathodes only has a slight influence, mainly because intermetallic phases form in the heat-affected zone of the cathode surface for both cathode types. In an Ar atmosphere, the influence of the Nb-Al cathode composition on ion properties is fading at higher pressures, while at lower pressures, Ar ions with high velocities similar to those of Nb and Al ions appear, indicating a participation of Ar in cathode spot processes.

AB - Cathodic arcs explosively transform the cathode material into a plasma, a phenomenon which is often utilized to deposit thin films, but can also serve as an ion source for other applications. Particularly for cathodic arc deposition, a better understanding of the influence of the cathode material to arc plasma properties is relevant. While extensive experimental data in literature led to a good comprehension of the relationship of single-element cathode materials to their arc plasma properties, effects introduced by multi-element cathode materials are explored less frequently and many open questions remain. For example, it is still unclear if physical concepts like the cohesive energy rule can be applied to multi-element cathodes. Therefore, a Nb-Al cathode model system was used within this work to study the effect of multi-element cathodes on arc properties. It includes pure Nb and Al cathodes, 3 intermetallic cathodes where each one is composed of one of the 3 intermetallic phases in the Nb-Al system, and 3 composite Nb-Al cathodes with atomic ratios corresponding to the stoichiometric ratios of the intermetallic phases. Pulsed cathodic arcs from these cathodes were examined in high time resolution by recording voltage and current of the discharges; by obtaining ion energy and charge state distributions in the arc plasma in high vacuum and Ar atmospheres; and by investigating converted layers of eroded cathodes. The results show that arc plasma properties from Nb-Al cathodes are quite different from the properties of their single-element counterparts and do not follow a simple linear interpolation between them like related cohesive energies. The composite/intermetallic morphology of bulk cathodes only has a slight influence, mainly because intermetallic phases form in the heat-affected zone of the cathode surface for both cathode types. In an Ar atmosphere, the influence of the Nb-Al cathode composition on ion properties is fading at higher pressures, while at lower pressures, Ar ions with high velocities similar to those of Nb and Al ions appear, indicating a participation of Ar in cathode spot processes.

KW - Lichtbogen

KW - Gepulster Lichtbogen

KW - Lichtbogenverdampfung

KW - Kompositkathoden

KW - Intermetallische Kathoden

KW - Nb-Al

KW - Zeitaufgelöste Messungen

KW - Ionenenergieverteilung

KW - Ionenladungsverteilung

KW - Ar Atmosphäre

KW - arc discharges

KW - cathodic arcs

KW - pulsed arcs

KW - composite cathodes

KW - intermetallic cathodes

KW - Nb-Al

KW - time-resolved measurements

KW - ion energy distribution

KW - ion charge state distribution

KW - Ar atmosphere

M3 - Doctoral Thesis

ER -