Determination of diffusion parameters in the quasi-single crystal thin film under stress

The hetero-epitaxial single crystal thin film is a model system for verifying the stress induced diffusion predicted by the Larché-Cahn diffusion theory. However, it is very often that a few grain boundaries may exist in the hetero-epitaxial thin film prepared by PVD technique. In order to determine the diffusion induced concentration profile by a depth profiling technique (e.g. AES, SIMS and GDOES), the stress induced bulk diffusion [1] and grain boundary diffusion [2] have to be taken into account. In this work, the concentration-depth profile in the quasi-single crystal thin film under stress is firstly calculated by considering both the stress induced bulk diffusion and grain boundary diffusion. Then, this calculated concentration-depth profile with adjustable diffusion parameters is convoluted with the so-called Mixing-Roughness-Information (MRI) depth resolution functions [3]. Finally, the diffusion parameters in the quasi-single crystal thin film under stress are obtained by fitting optimally the convoluted concentration-depth profile to the measured one.

References

[1] F. Larché, and J.W. Cahn, A linear theory of thermochemical equilibrium of solids under stress, Acta Metallurgica, 21 (1973) 1051.

[2] L. Klinger, and E. Rabkin, Theory of the Kirkendall effect during grain boundary interdiffusion, Acta Materialia, 59 (2011) 1389.

[3] J.Y. Wang and E.J. Mittemeijer, A new method for the determination of the diffusion-induced concentration profile and the interdiffusion coefficient for thin solid film systems by Auger electron spectroscopical sputter depth profiling, Journal of Materials Research, 19 (2004) 681.