Fundamental investigations of interlayer processes occurring during DLC coating of selected plastics

如今，塑料材料因其优越的性能(弹性和重量轻)而被广泛应用于许多领域。然而，它们的一些不利特性(低硬度和低磨损强度、微生物粘附性)在很大程度上限制了它们在某些应用领域(如医药)的使用。通过在传统塑料表面涂覆类金刚石碳(DLC)，可以改善其性能，从而扩大其应用范围。DLC层通常被认为是坚固、抗菌和生物相容的保护层。虽然DLC层可以被涂覆在许多材料上，但DLC涂层塑料的研究仍然很少。尤其是初始涂层过程中原始表面的化学和物理性质的变化尚不完全清楚。本研究项目的目的是阐明和确定等离子体辅助在所选塑料(聚乙烯、聚甲醛)表面沉积DLC层的过程。研究工作将侧重于详细解释薄膜生长过程中的初始过程，以及伴随而来的对软塑材料和硬类金刚石边界层的修改。普遍的反应过程将被划分为沉积、层间形成和侵蚀等可能的过程类型，只有极少的原子层被沉积以分析新出现的边界层。在镀膜过程中，利用高分辨率质谱仪连续观察反应室中各组分的组成。这有助于阐明哪些等离子体与衬底发生相互作用，以及改变工艺参数可以在多大程度上影响这种相互作用。我们希望使用各种X射线光谱分析方法(XPS，NEXAFS)获得关于DLC层和衬底之间边界层结合性质的相关信息。此外，除了涂层参数外，还假设化学成分和衬底表面以及沉积DLC的量对所产生的结合(边界层)和所得到的涂层塑料材料的形貌有影响。本项目的目的是对硬(DLC)和软(塑料)材料之间的结合有一个基本的了解。使用的塑料材料作为典型的模型基板。结果将转移到其他聚合物材料，从而使未来能够生产具有改变表面特性的替代材料，例如低磨损行为，同时具有柔性和生物相容性的表面。

Nowadays plastic material can be found in many fields of application due to their advantageous properties (elasticity and low weight). However, some of their disadvantageous characters (low hardness and abrasion strength, microbial adhesion) limit their use considerably in some fields of application (e.g. medicine). Properties can be improved and consequently applications of conventional plastic material can be extended by coating them with diamond-like carbon (DLC). Generally DLC layers are considered to be robust, anti-bacterial and bio-compatible protective layers. Although DLC layers can be coated on a high number of materials, DLC-coated plastics are yet sparsely investigated. Especially the changes of the chemical and physical properties of the original surface during the initial coating process are yet thoroughly unclear.The purpose of this research project is to elucidate and define the processes that take place during the plasma-assisted deposition of DLC layers on the surface of chosen plastics (polyethylene, polyoxymethylene). Research work will especially focus on the detailed explanation of the initial process during the growing of the layers and the accompanying modifications on the boundary layer between soft plastic material and hard DLC. The prevalent reaction processes will be assigned to the possible process types like deposition, interlayer formation and erosion.Only very few atomic layers are deposited in order to analyze the emerging boundary layer. The composition of the components in the reaction chamber is being observed continuously during the coating process with the help of high-resolution mass spectroscopy. This serves to clarify which plasma interaction takes place with the substrate and how far this can be influenced by varying the process parameters.We expect to obtain relevant information concerning the binding properties on the boundary layer between the DLC layer and the substrate using various x-ray spectroscopy methods (XPS, NEXAFS). Furthermore it is assumed that apart from the coating parameters also chemical composition and the surface of the substrate as well as the amount of deposited DLC have influence on the resulting bonding (boundary layer) and the resulting morphology of the coated plastic material.The purpose of this project is to achieve a basic understanding of the bonding between hard (DLC) and soft (plastic) materials. The used plastic materials serve as typical model substrates. The results will be transferred to other polymer materials thus enabling the production of alternative materials with changed surface characteristics such as low abrasive behavior and at the same time flexible as well as biocompatible surfaces in the future.