| Summary: | 碩士 === 國立清華大學 === 材料科學工程學系 === 105 === The electric field control of magnetism has drawn a lot of attention due to the need of reducing writing current densities on MRAM devices.
This thesis focus on tuning FePt for ordering and (001) preferred orientation. On Si / SiO¬2 ¬ substrates, we tune the rapid thermal annealing process and FePt composition and introduce FeOx as capping layer or underlayer. We obtain ordering in FePt films of thickness 2, 3, and 4.5 nm with (001) preferred orientation. The reduction of FeOx to Fe on rapid thermal annealing process promotes the diffusion of Fe and Pt atoms, which leads to a better (001) preferred orientation. The perpendicular anisotropy is suit for analogous Hall measurement, which is often needed after device patterning and further spin Hall angle measurement.
FePt on Pt 5 nm electrode also achieve perpendicular anisotropy by inserting ultrathin SiO2 insertion layer. The insoluble SiO2 insertion layer will diffuse through gran boundaries of FePt during rapid thermal annealing process and also promote the diffusion of Fe and Pt atoms. That leads to a lower ordering temperature.
The RRAM characteristic of SrTiO3 dielectric layer is also tested. With different forming process, SrTiO3 can achieve unipolar switching and bipolar switching. The ferroelectric like IV curves also been observed. Further examination is needed to ensure the properties of SrTiO3 is ferroelectric or not. The cycling test and retention test shows stable RRAM characteristic of SrTiO3.
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