Cathode spot behavior in nitrogen and oxygen gaseous atmospheres and concomitant cathode surface modifications

Abstract

The cathode spot behavior influences the arc plasma chemistry and film growth conditions during reactive cathodic arc deposition of nitride and oxide films. Cathode spots can be studied using their characteristic craters left behind on the cathode surface. The multilayer cathode design used in this study reveals temporal and spatial progress of cathode spots by enabling three-dimensional visualization of the craters. The surface nitridation or oxidation of the cathode, also known as cathode poisoning, was found to give rise to a repeated switching between cathode spots of type 1 and 2. The surface oxide layers, however, more significantly promote the ignition of type 1 spots due to their thermodynamically privileged formation and/or their more favorable physical properties building up a stronger electric field within the insulating layer. The crater depths and their contribution to the surface modification of multilayered cathodes are discussed in detail. These results may contribute to a better understanding of macroparticle generation and arc plasma properties in cathodic arc deposition processes. • Cathode spot repeatedly switches between type 1 and 2 in reactive atmospheres. • Surface oxidation promotes stronger ignition of cathode spot type 1. • Material intermixing predominately occurs in liquid state. • Deep type 2 craters are main contribution to material intermixing. • Shallow type 1 craters contribute to material intermixing in oxygen.