“…180,181 The usage of cathodes with a low ionization potential will even cause a faster "dark spot degradation" due to the higher affinity to oxygen. 15,236 Besides these explanations for dark spot growth, a few other theories are worth noting: For instance, an interdiffusion of materials, made possible by internal Joule heating, was proposed, which should result in exciton quenching sites and parasitic current pathways. Such an interdiffusion may occur at the dark spot margin due to the high currents, which will lead to a further spot growth.…”