Regensburg 2007 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 20: Poster session

MM 20.28: Poster

Tuesday, March 27, 2007, 14:45–18:00, Poster C

Reactive interdiffusion in sandwich type Al/Cu thin-films — •Constantin Buzau Ene¹, Carsten Nowak¹, Guido Schmitz², Talaat Al-Kassab¹, and Reiner Kirchheim¹ — ¹Institut für Materialphysik, Friedrich-Hund Platz 1, D-37077, Göttingen, Germany — ²Institut für Materialphysik, Wilhelm-Klemm-Str.10, D-48149 Münster, Germany

Al/Cu/Al and Cu/Al/Cu triple layers with approximately 10nm single layer thickness deposited on tungsten substrates and planar (100) Si were analyzed in the early stages of reactive interdiffusion by atom probe tomography and TEM. The first reaction product is found after 5 min at 110^∘C and identified with a composition around the Al₂Cu. Surprisingly, we found a significant asymmetry in the reaction rate with the stacking sequence as a particularity of the tip-shaped tungsten tips: The thickness of the product grown at the interfaces Cu grown on Al layer, is approximately 1.5 to 2 times thicker than at the other interfaces at which Al grows on a Cu layer. Compared to the recently proven delayed nucleation of the first product phase in the case of Al/Co thin-films, which has been explained by the concept of a critical gradient, the reaction in Al/Cu develops quite differently. Applying the critical gradient concept to the Al/Cu system leads to the prediction of a critical nucleation thickness of 6.8 nm. This is in obvious contrast to the experiment, which reveal parabolic growth from the very beginning with no precursory interdiffusion and no distinct nucleation process. Thus,in the case of Al/Cu the first reaction product might be a metastable one. Pasichnyy et al, Phys. Rev. B 72 (2005).