Studies on vacuum arc evaporation behavior of modified graphite cathodes and influence on particle-induced defects in deposited (t)a-C films with and without dopant

在薄膜PVD工艺中，真空电弧工艺在工具和部件应用的硬质和耐磨涂层的沉积中发挥着重要作用。除了存在几乎完全电离的高能涂层等离子体之外，主要优点是稳健的蒸发技术，该技术允许在涂层的工业沉积期间进行稳定和有效的工艺控制。超硬，四面体无定形碳（ta-C）涂层电弧工艺生产在这方面发挥着特殊的作用。由于其几乎普遍有利的摩擦学性能，它们正在越来越多的应用中使用。对于电弧工艺的所有提到的优点，它们也具有固有的缺点，即液滴或颗粒排放，这与来自蒸发的阴极材料的电弧的阴极点处的放电过程内在地相关。这种现象在ta-C涂层中特别明显，并导致沉积涂层中的缺陷和硬粗糙度峰值，这使得涂层不能用于许多应用或需要在后平滑涂层中付出很大努力。在这方面的一个根本性的新的方面已经证明在最近的工作：在调查中与低元素添加（5原子%）的石墨阴极，掺杂ta-C薄膜的生产表现出粒子诱导的缺陷密度，这是相当大的一部分，高达10倍的低。这种情况是令人惊讶的，因为蒸发的阴极仍然由95%的石墨组成。有很大的元素依赖性的颗粒减少的差异。因此，B和Mo引起了很强的，而Si引起的粒子诱导缺陷密度几乎没有变化。在ta-C（：X）薄膜中，掺杂剂引起的颗粒减少现象是一个以前未被探索过的、科学上有趣的现象，应该被彻底研究和理解。本研究项目的总体目标是了解在电弧蒸发石墨和复合石墨阴极过程中影响颗粒形成的关键因素，并将其纳入生长的（t）a-C：X薄膜。在阴极的过程和现象，在等离子体和薄膜生长将被分析和考虑的背景下，以了解在掺杂的ta-C层的颗粒减少的决定性影响，并从中获得合适的模型。

Among the thin film PVD processes, the vacuum arc process plays a prominent role in the deposition of hard and wear-protective coatings for tool and component applications. The main advantage, in addition to the presence of an almost completely ionized, high-energy coating plasma, is a robust evaporation technology that allows stable and efficient process control during industrial deposition of the coatings. Superhard, tetrahedral amorphous carbon (ta-C) coatings produced by arc processes play a special role in this context. Thanks to their almost universally favorable tribological properties, they are being used in an increasing number of applications. For all the mentioned advantages of arc processes, they also have an inherent disadvantage, namely droplet or particle emission, which is intrinsically linked to the discharge process at the cathode spot of the arc from the vaporized cathode material. This phenomenon is particularly pronounced in ta-C coatings and leads to defects and hard roughness peaks in the deposited coatings, which make the coatings unusable for many applications or require a great effort in post-smoothing the coatings. A fundamentally new aspect in this context has been demonstrated in recent work: In investigations with low element additions (5 at%) to graphite cathodes, doped ta-C films were produced which exhibited a particle-induced defect density that was in part considerable, up to a factor of 10 lower. This circumstance is surprising in that the evaporated cathodes still consisted of 95% graphite. There were large element-dependent differences in particle reduction. Thus, B and Mo caused a very strong, while Si caused almost no change in the particle-induced defect density. The phenomenon of particle reduction in ta-C(:X) films by dopants is a previously unexplored, scientifically interesting phenomenon that should be thoroughly investigated and understood. The overall objective of this research project is to develop an understanding of the key factors influencing the formation of particles during arc evaporation of graphite and composite graphite cathodes and their incorporation into the growing (t)a-C:X films. The processes and phenomena at the cathode, in the plasma and in the film growth will be analyzed and considered in context in order to understand the decisive influences on the particle reduction in doped ta-C layers and to derive suitable models from them.