Relationship between deposition parameters and the properties of RF-magnetron sputter deposited zirconia thin films

Although ceramic materials have many properties that make them desirable in a number of applications, their use is limited by their brittle nature. The fracture behavior of ceramics depends greatly on flaws in the material. It is almost always the case that the critical flaw responsible for catastrophic failure is a surface flaw. In order to improve the fracture resistance of ceramic materials, it is reasonable to explore modifying the surface by the application of a thin film.; In order to preserve the optical and chemical properties of a ceramic substrate, a ceramic coating material was required. Yttria stabilized zirconia (YSZ) was selected as the coating material due to its high toughness. RF-magnetron sputtering was chosen as the deposition method because of its versatility, especially the ability to deposit at low temperatures.; Initial depositions designed to explore the film properties achievable indicated that a variety of crystal compositions and film stoichiometries were possible. The grain morphology remained columnar in all cases. Alumina bars coated by YSZ films displayed higher fracture resistance than uncoated controls, but there was no significant difference among the coated groups. This indicated that the columnar structure was the most important factor in determining how effective coatings were in enhancing fracture properties.; Cyclic use of substrate bias and deposition interruption were both attempted to disrupt the columnar structure. Deposition interruption was not effective, but cyclic bias sputtering was. A multilayer structure consisting of alternating layers of biased and unbiased YZ was formed. The biased layers did not have a columnar structure. Mechanical tests indicated that alumina bars coated with multilayer films had superior fracture properties compared to bars coated with monolayer films.; Grain size was determined by transmission electron microscopy (TEM). The grain size did not change significantly regardless of deposition condition. TEM was also used to elucidate texturing effects observed in the biased thin films. It was further observed that the interfaces became less distinct with increasing number of layers, indicating that simply increasing the number of layers would not be effective in improving the enhancement of fracture properties.