Wingbermühle, J. (Corresponding author)FZJ*

2002
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Report No.: Juel-3973

Abstract: This thesis deals with the installation and characterization of an Ion-beam-Sputtering machine. There were a lot of technical problems during that period, for instance the contamination of the deposited layers. XPS-measurements revealed a value of 4.3% for the Fe-contamination. The divergence of the ion-beam was identified as the source of the contamination. A significant fraction of the ion-beam missed the target, hit the chamber wall and sputtered its material. By using an aperture the beam-diameter was decreased and the Fe-contamination could be reduced to 0.5%. Furthermore the determination of the optimal parameters for sputtering Look a lot of time. Experiments which were made at the end of this thesis showed a significant improvement of the quality of the layers when optimal parameters were used. The RMS-values of these layers were in the range of 1$\mathring{A}$ TEM-pictures showed a polycrystalline growth of Co and Py. The growth of AIN is also polycrystalline-like, and the interfaces between AIN and both Co and Py are very smooth. Despite of the contamination, tunnel junctions with different nitration-mechanisms (nitration of an Al-layer or reactive sputtering of AIN) have been fabricated. XPS-measurements proved the existence of AIN in the layer. Measurements of the conductivity revealed that the direct tunneling process alone is not sufficient for the description of the temperature- and bias dependence. The influence of localized states in the barrier had to be taken into account. Therefore the measurements of the conductivity provide a good method for the investigation of the barrier quality. Patterned Samples showed a TMR-value of 1% at 20 K, which could be explained with the high value of contamination. A comparison with the UV-oxidized tunneljunctions yielded a clear difference between the energy involved in the processes during the barrier fabrication. This is an additional reason for the low TMR-value of the AIN-TMR-junctions.

Keyword(s): ion beam technology ; sputtering ; tunnel junction ; magnetoresistance

1. Elektronische Eigenschaften (IFF-9)