Development of FexN thin films with microcompression analysis

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.Open Acces

Effect of Kaolin Geopolymer Ceramics Addition on the Microstructure and Shear Strength of Sn-3.0Ag-0.5Cu Solder Joints during Multiple Reflow

Solder interconnection in three-dimensional (3D) electronic packaging is required to undergo multiple reflow cycles of the soldering process. This paper elucidates the effects of multiple reflow cycles on the solder joints of Sn-3.0Ag-0.5Cu (SAC305) lead (Pb)-free solder with the addition of 1.0 wt.% kaolin geopolymer ceramics (KGC). The samples were fabricated using powder metallurgy with the hybrid microwave sintering method. Apart from using conventional cross-sectioned microstructure imaging, advanced synchrotron real-time in situ imaging was used to observe primary IMC formation in SAC305-KGC solder joints subjected to multiple reflow soldering. The addition of KGC particles in SAC305 suppressed the Cu6Sn5 IMC’s growth as primary and interfacial layers, improving the shear strength after multiple reflow soldering. The growth rate constant for the interfacial Cu6Sn5 IMC was also calculated in this study. The average growth rate of the primary Cu6Sn5 IMCs decreased from 49 µm/s in SAC305 to 38 µm/s with the addition of KGC particles. As a result, the average solidified length in the SAC305-KGC is shorter than SAC305 for multiple reflow soldering. It was also observed that with KGC additions, the growth direction of the primary Cu6Sn5 IMC in SAC305 changed from one growth to two growth directions. The observed results can be attributed to the presence of KGC particles both at grains of interfacial Cu6Sn5 IMCs and at the surface of primary Cu6Sn5 IMC

Metal-Doped TiO₂ Thin Film as an Electron Transfer Layer for Perovskite Solar Cells: A Review

The electron transfer layer (ETL) plays a vital role in achieving high-performance perovskite solar cells (PSCs). Titanium dioxide (TiO2) is primarily utilised as the ETL since it is low-cost, chemically stable, and has the simplest thin-film preparation methods. However, TiO2 is not an ideal ETL because it leads to low conductivity, conduction band mismatch, and unfavourable electron mobility. In addition, the exposure of TiO2 to ultraviolet light induces the formation of oxygen vacancies at the surface. To overcome these issues, doping TiO2 with various metal ions is favourable to improve the surface structure properties and electronic properties. This review focuses on the bulk modification of TiO2 via doping with various metal ions concentrations to improve electrical and optical properties, charge carrier density, and interfacial electron–hole recombination, thus contributing to enhancing the power conversion efficiency (PCE) of the PSCs

High-Entropy Alloy for Thin Film Application: A Review

High entropy alloy (HEA) involves the addition of five or more elements into the materials system. This provides a multidimensional configuration space that is limitless in terms of its properties and functions. Some high-entropy alloys have already been shown to have superior properties over conventional alloys, especially the CoCr-based HEA materials. Better high-entropy alloy applications may be discovered, especially in micro- and nano-level structures, hence the development of thin film/coating -based HEA materials. Therefore, in this review paper, we are aiming to provide recent studies on the thin film/coating-based high-entropy alloy on fundamental issues related to methods of preparation, phase formation and mechanical properties. We found that sputtering has been extensively used to grow thin-film-based HEAs as it allowed parameters to be controlled with homogeneous growth. The evolution from bulk to thin samples can also be observed with the mechanical properties has exceeded the bulk-based HEA expectations, which are high hardness, better interfacial bonding and tribological behaviour and higher corrosion resistant