Oral Presentation 26th ACMM “2020 Visions in Microscopy”

Invited talk - Diffusion phenomena in nitride multilayer thin films as observed directly by aberration-corrected TEM methods. (#89)

Magnus Garbrecht 1 , Vijay Bhatia 1 , Ingrid McCarroll 1 , Ashalatha Indiradevi Kamalasanan Pillai 1 , Limei Yang 1 , Julie M Cairney 1 , Bivas Saha 2
  1. The University of Sydney, The University Of Sydney, NSW, Australia
  2. Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Jakkur, Bangalore 560064, India

Device failure from diffusion short circuits in microelectronic components occurs via thermally induced migration of atoms along high-diffusivity paths: dislocations, grain boundaries, and free surfaces [1-3]. Knowledge about the structural features along which diffusion paths are formed is hence of great importance, since even well-annealed single-grain metallic films contain dislocation densities of about 1014 m-2; hence dislocation-pipe diffusion (DPD) becomes a major contribution at working temperatures. While its theoretical concept was established already in the 1950s [4] and its contribution is commonly measured using indirect tracer, spectroscopy, or electrical methods [5], no direct observation of DPD at the atomic level has been reported until very recently [6].

We present atomically resolved STEM images of the onset and progression of diffusion along threading dislocations in sequentially annealed nitride metal/semiconductor superlattices [7-10]. The STEM micrographs showing the same region at different time-steps during annealing are accompanied by EDS maps and GPA analysis, and diffusivity coefficients are calculated directly from them. We show that this type of diffusion is independent of concentration gradients in the system but governed by the reduction of strain fields in the lattice [6]. The study of diffusion in this type of superlattices is important for the understanding of their potential applications at elevated temperatures [11-12].

Secondly, we present STEM imaging and EDS mapping in tandem with atom probe tomography of another metal/semiconductor superlattice thin film as a model system to discuss the advantages of atomic resolution STEM and APT by comparing results obtained from the same superlattice sample and show that pitfalls of the individual techniques can be overcome by combining them [13].

Aberration-corrected STEM was employed using Sydney Microscopy & Microanalysis' image- and probe-corrected and monochromated FEI Themis-Z 60-300 kV instrument equipped with a high-brightness XFEG source and Super-X EDS detector for ultra-high count rates.

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  4. R. Smoluchowski, Phys. Rev. 87, (1952).
  5. H. Mehrer, Diffusion in Solids, Springer Series in Solid State Sciences, vol. 155, Berlin, 2007.
  6. M. Garbrecht, B. Saha, J. L. Schroeder, L. Hultman, and T. D. Sands, Sci. Rep. 7, (2017).
  7. T. D. Sands, C.J. Palmstrøm, J.P. Harbison, V.G. Keramidas, N. Tabatabaie, T.L. Cheeks, Y. Silberberg, Mater. Sci. Rep. 5, (1990).
  8. J. L. Schroeder B. Saha, M. Garbrecht, N. Schell, T. D. Sands, and J. Birch, J. Mater. Sci. 50, (2015).
  9. B. Saha, Y. Rui Koh, J. Comparan, S. Sadasivam, J. L. Schroeder, M. Garbrecht, A. Mohammed, J. Birch, T. Fisher, A. Shakouri, and T. D. Sands, Phys. Rev. B. 93, (2016).
  10. M. Garbrecht, J. L. Schroeder, L. Hultman, J. Birch, B. Saha, and T. D. Sands, J. Mater. Sci. 51(17), (2016).
  11. M. Garbrecht, L. Hultman, M. H. Fawey, T. D. Sands, and B. Saha, Phys. Rev. Materials 01, (2017).
  12. M. Garbrecht, L. Hultman, M. H. Fawey, T. D. Sands, and B. Saha, J. Mater Sci. 53(6) (2018).
  13. M. Garbrecht, I. McCarroll, L. Yang, V. Bhatia, B. Biswas, D. Rao, J. Cairney, and B. Saha, under review (2019).