Fachbereich 11 - Physik
Institut für Materialphysik
Nanoanalysis of Interreactions

Nucleation of product phase at reactive diffusion of Co/Al

The reaction of Co/Al bi-layers was investigated by means of atomprobe tomography. For that tip-shaped reaction couples were produced by sputter deposition onto tungsten substrates. The reaction couple Co/Al is a rather clear example, where the formation of a unique product (Al₉Co₂) is indicated by two distinct heat releases in DSC traces. The nano-analysis directly proved the existence of two distinct reaction stages, i) nucleation and lateral growth along the interface and ii) normal growth. Furthermore interdiffusion on the length scale of only 3-4 nm has been proven as an precursor of the reaction for the first time. The naive picture of reaction step i) must be modified, since already in this state some thickness growth takes place by interfacial transport along the product particle surface. By a quantitative analysis it was shown that this behaviour leads to a thickness of about 10 nm when reaction stage i) is completed.

Drittmittelgeber:

Deutsche Forschungsgemeinschaft (SFB 602)

Beteiligte Wissenschaftler:

V. Vovk, R. Kirchheim (Univ. Göttingen), G. Schmitz (Projektleiter)

Veröffentlichungen:

V. Vovk, R. Kirchheim and G. Schmitz, Three-dimensional atomprobe investigation of Co/Al thin film reaction, Microelectr. Eng. (2003) in press