Strukturelle und magnetische Eigenschaften nanostruktuierter Systeme

The subject of this diploma thesis is the investigation of the structural and magnetic properties of nanostructured dot lattices and wires. These systems are made by EBL (electron beam lithography) and a conventional metal vapour deposition process. The aim of this thesis is to show the possibility of the production of large area magnetic dot lattices with minimum diameter for a macroscopic magnetization measurement. The determination of the necessary parameters for the EBL has been done on special gold test-structures. Using these test-structures the optimisation of the spin-on process and the writing and development parameters was carried out. The resist mask was examined using an atomic force microscope (AFM) after the writing process and the development. After metal deposition, the size and shape of the nanostructures were controlled with a scanning electron microscope (SEM). The structural properties of the magnetic system were determined using a transmission electron microscope (TEM). Using these parameters large area magnetic dot lattices composed of (Co/Pt)10 – multilayers having perpendicular magnetic anisotropy were fabricated. The magnetic properties were studied by magnetization measurements using SQUID magnetometry. Complete hysteresis loops taken at different temperatures gave the temperature dependence of the saturation magnetization and the coercive field of the multilayers. Because of the small mass of the multilayers, the SQUID signal is rather weak in comparison to the signal of the substrate. Nevertheless, using a specially developed sample holder, the influence of the substrate could be separated from the signal caused by the dot lattice. However, using this set-up, the accuracy of the results are limited to only within +/- 40%. Another important aspect of this thesis was the production of magnetic nanowires with macroscopic non – magnetic bondpads for electrical resistivity measurements. First, the nanowires and special marks are written on the substrate. In the second step the gold bondpads are placed over the wires within a precision of 50 nm.


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