INTRODUCTION
In optimizing various nano-scale manufacturing technologies, it is essential to consider the evolution mechanisms of thin film structures. The potential applications of thin film structures include but are not limited to the surface coating of microelectronic devices and manufacturing of metal nano-wires.
The structures with minimal grain boundaries can achieve more uniform material property throughout the overall structure, which leads to a reduced risk of detrimental anisotropy and shape changes. However, there is a great deal of difficulty in manufacturing a single-grained structure, even at a nano-scale. Therefore, it is critical for manufacturers to understand the properties of the multi-grained structures to be able to anticipate and reduce the risks of the defects.
ME 574 lectures and previous ME 574 projects have covered some of the simplest cases of thin film interface migration and diffusion. This project builds off of the previous analyses done on single-layered thin film structures as it expands the scope of the problem to structures with much more complex geometries. In particular, single-layered thin film structures with multiple grain boundaries and multi-layered thin film structures were studied in depth. The study aims to identify which of the vertical or horizontal grain boundary results in a more dramatic shape change of the overall film structure.
OBJECTIVES
The main objective of this project is to investigate the effects of various grain boundary geometries on the evolution of thin film structures. While ME 574 lectures have covered the solutions to a steady state diffusion and migration of a simple, single-layered film with one vertical grain boundary, this project investigates the evolutions of multi-grained thin films. The following two problems were analyzed closely:
- Evolution of multiple grain boundaries in a single-layered thin film structure
- Evolution of multi-layered thin film structures
This problem investigates how the presence of multiple grain boundaries would affect the evolution of a thin film structure. A single-layered film was divided into several portions by inducing multiple vertical grain boundaries. The effects of the distance between each of the grain boundaries on the interface migration speed as well as the resulting geometry of the overall structure were analyzed.
This problem investigates the effects of stacking up thin film structures on top of each other on the evolution of the overall structure. The two-layered thin film structure with various combinations of the top and the bottom layer thicknesses were developed. The relationship between the top and bottom film thicknesses and their interface migration speeds as well as the resulting geometries of the overall structure was investigated. In addition, the consequences of the top layer not having an immobile bottom interface (unlike the original single-layered problem) were investigated.