Development of FexN thin films with microcompression analysis

Abstract

This thesis explores the growth routes of metal nitrides based materials of binary and ternary nitrides. It is believe that this iron nitrides based materials exhibit interesting properties in term of electronic optical, thermal and magnetic properties. However, most experimental and analytical efforts in this research field have been carried out in the form of bulk samples and there was no research of these nitrides in thin films. Consider the unique characteristics of iron nitrides system, the binary and ternary nitrides of both FexN and FexWy-1N thin films were grown using electron beam physical vapor deposition method under metal rich conditions. There exist significant challenges for the development of both binary and ternary nitrides thin films. It required to remain stable during the growth in order to incorporate nitrogen in the system to obtain Fe-N system due to the nature of nitrogen of having strong triple bond. The first aspect of this thesis investigate the development of these nitrides by using four different methods. Results from XRD and XPS reveal that there were formation of iron oxides on the thin films and further XPS data shows the percentage of nitrogen is lower than expected. The highest content of iron was then selected to proceed with second phase of the project with the aim of developing iron nitrides thin films with thicker films under higher growth temperature. The formation of iron nitrides were found in the thin films with higher growth temperature. The XPS analysis that shows the presence of either Fe2+ or Fe3+ species in the sample and further investigation by TEM reveals the film hexagonal crystal structure which corresponds to Fe3N. An attempt of growing ternary nitrides were carried out with different iron to tungsten ratio. However, in this preliminary study, we only managed to obtain W-N composition with a limited amount of iron presence in the sample. It was found that either the iron has been oxidised or some iron oxides or tungsten oxides were formed during the synthesis Microcompression experiment was carried out on the thicker iron nitrides thin films in order to calculate their Young’s modulus. It was found that the value is still lower than the bulk samples which may be corresponds to misalignment between the pillar and the system during the experiments. However, it was observed that there was no deformation such as crack occurred on the thin films during this test. Further study shall be carried out to have a better understanding of these iron nitrides based thin films.