Synthesis And Characterization Of Cu (Nb) Alloyed Fe-N Films And Fe-N/Si-N Multilayer Films

Fe-N films have been widely studied due to their high corrosion/wear resistance and good mechanical properties. Recently, ferromagnetic iron nitride compounds, such asα?-Fe16N2,γ?-Fe4N, andε-Fe3N, have been considered to be potential applications as magnetic heads for high-density recording. However, some disadvantages have been found in pure Fe-N single layer films for the potential applications as magnetic heads, which are required to be soft and high thermal stability as well. In trying to improve the magnetic and other properties of Fe-N films, many investigations on the doped Fe-N film (microstructure adjustment) and mutillayer Fe-N film (macrostructure adjustment) have been carried out. In this thesis, the syntheses and characterization of Cu (Nb) alloyed Fe-N film and Fe-N/Si-N mutillayer films grown by direct current magnetron sputtering are investigated systemically, and the obtained conclusions are summarized as follows:1. Effect of Cu-addition on the structure, magnetic, and thermal stability for Fe-N filmsCu-addition iron nitride films were prepared on Si (100) substrates by facing-targets magnetron sputtering, and the effects of Cu addition on the structural,thermal stability, and magnetic properties of Fe–N films were explored. It was found that the film with Cu content of 5 at % showed good soft magnetic properties as well as the thermal stability, in which the coercivity was reduced from 122 to 8 Oe, and the Cu-addition iron nitride was stable even at 500 ?C. For the film with Cu content of 50 at %, the film containing Fe1-xCux nitride and pure Cu was formed after annealing, the coercivity increased from 129 to 289 Oe.2. Effect of Nb-addition on the structure, magnetic, and mechanical properties for Fe-N filmsFe-Nb-N films (Nb content: 5 and 25 at %, respectively) were prepared on Si (100) substrates by facing-targets magnetron sputtering, and the structure, magnetic, and mechanical properties of as-deposited and annealed Fe–Nb-N films were explored. It was found that the annealed Fe-Nb-N film with Nb content of 5 at % was composed of aε-Fe3N phase, and Nb-addition improved both the magnetic and mechanical property of Fe-N film, in which the value of saturation magnetization, coercivity, and hardness for Fe-Nb-N film was 164 emu/g, 9 Oe, and 12 GPa, respectively. Also, it was found that as Nb content increased to 25 at %, the hardness for Fe-Nb-N film increased up to 16.7 GPa.3. Influence of Si-N interlayer on the microstructure and magnetic properties ofγ'-Fe4N filmsThe (γ'-Fe4N/Si-N)n (n: number of layers) multilayer films andγ'-Fe4N single layer film synthesized on Si (100) substrates by direct current magnetron sputtering were annealed at different temperatures. The structures and magnetic properties of as-deposited films and films annealed at different temperatures were characterized. The results showed that the insertion of Si-N layer had a significant influence on the structures and magnetic properties ofγ'-Fe4N film. Without the addition of Si-N lamination, the iron nitrideγ'-Fe4N tended to transform toα-Fe when annealed at the temperatures over 300 oC. However, the phase transition fromγ'-Fe4N toε-Fe3N occurred at annealing temperature of 300 oC for the multilayer films. Furthermore, with increasing annealing temperature up to 400 oC or above,ε-Fe3N transformed back intoγ'-Fe4N. The magnetic investigations indicated that the coercivity of magnetic phaseγ'-Fe4N for as-deposited films decreased from 152 Oe (for single layer) to 57.23 Oe with increasing n up to 30. For the annealed multilayer films, the coercivity values decreased with increasing annealing temperature, except that the film annealed at 300 oC due to the appearance of phaseε-Fe3N.In summary, Cu (Nb)-addition Fe-N films and (γ'-Fe4N/Si-N)n multilayer films were deposited by DC magnetron sputtering using a mixture of Ar and N2 gas. The structures, magnetic properties, and mechanical properties were characterized using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Vibrating sample magnetometer (VSM) and Nanoindentation. The effect of Cu (Nb) addition and Si-N interlayers on the structure, magnetic, and mechanical properties for Fe-N films were explored.