Effects of Cu underlayer on the structure of Fe50Mn50 films were studied. Samples with a structure of Fe50Mn50（200 nm）/ Cu(tCu) were prepared by magnetron sputtering on thermally oxidized silicon substrates at room temperature. The thickness of Cu underlayer varied from 0 to 60 nm in the intervals of 10 nm. High-vacuum annealing treatments, at different temperatures of 200, 300 and 400 ℃ for 1 h, respectively, on the Fe50Mn50（200 nm）/ Cu（20 nm） thin films were performed. The surface morphologies and textures of the samples were measured by field emission scan electronic microscope （FE-SEM） and X-ray diffraction（XRD）. Energy dispersive X-ray spectroscopy （EDX） and Auger electron spectroscopy（AES） were used to analyze the compositional distribution. It is found that Cu underlayer has an obvious induce effect on （111） orientation of Fe50Mn50 thin films. The induce effects of Cu on （111） orientation of Fe50Mn50 changed with the increase of Cu layer thickness and the best effect was obtained at the Cu layer thickness of 20 nm. High-vacuum annealing treatments cause the migration of Mn atoms towards surface of the film and interface between Cu layer and substrate. With the increasing annealing temperature, migration of Mn atoms is more obvious, which leads to a Fe-riched Fe-Mn alloy film.
Fe-O/AlO_x/Fe-O tunnel junctions were prepared by reactive magnetronsputtering under mixed working gas Ar+2 percent O_2. The insulating AlO_x layer of 1-2nm thicknesswas sputtered directly from A1_2O_3 target. Electrode layers were made of 80at. percent iron and20at. percent oxygen. Bottom Fe-O electrode deposited on glass substrate annealed at 473K at thepressure of 3 X 10^(-4) Pa for an hour shows disparate crystalline grain structure, lower electricalresistance and coercivity compared to the as-deposited top electrode. Only crystalline structrureof alpha-Fe is observed in both electrodes. Large tunnel magnetoresistance in large Fe-O/AlO_x/Fe-Ojunctions of 1cm^2 is observed at room temperature and the I-V characteristic curve of the junctionshows that the barrier of the junction is of high quality.
L.Q. Pan, H. Qiu. F.P. Wang, P. Wu.Y’. Tian and S. Luo Department of Physics. University of Science and Technology Beijing, Beijing 100083, China Beijing Keda-Tianyu Microelectronic Materials Technology Development Co. Ltd., Rm 105 Keji Building. 30 Xueyu
Permalloy Ni_(80)Fe_(20) films have been grown on thermal oxidized Si (111)wafers by magnetron sputtering at well-controlled substrate temperatures of 300, 500, 640 and 780 Kin 0.65 Pa argon pressure. The base pressure was about 1x10^(-4) Pa. The deposition rate was about 5nm/min for all the films. The structure of the films was studied using X-ray diffraction, scanningelectron microscopy and atomic force microscopy. The composition of the films was analyzed usingscanning Auger microprobe. The resistance and magnetoresistance of the films were measured usingfour-point probe technique. The results show that the content of oxygen in the films decreasesgradually with raising substrate temperature. In addition, the surface morphology of the filmspresents notable change with the increasing of the substrate temperature; the residual gases anddefects decrease and the grains have coalesced evidently, and then the grains have grown upobviously and the texture of (111) orientation develops gradually in the growing film. As a result,the resistivity reduces apparently and magnetoresistance ratio increases markedly with raisingsubstrate temperature.
