The earliest stage of phase growth in sharp concentration gradients

B. Parditka, J. Tomán, C. Cserháti, Zs Jánosfalvi, A. Csik, I. Zizak, R. Feyerherm, G. Schmitz, Z. Erdélyi

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Phase nucleation in sharp concentration gradient and the beginning of phase growth is investigated in Ni-Si and Co-Si systems experimentally and by computer simulation. We applied a combination of X-ray diffraction, four-wire resistance, grazing incidence X-ray fluorescence analysis and extended X-ray absorption fine structure spectroscopy in fluorescence detection with X-ray standing waves for the depth profiling of a-Si/Ni/a-Si (and a-Si/Co/a-Si) layers with nanometer resolution. We observed that a mixture of Ni and Si with a 2:1 composition ratio is formed at the interfaces during sample preparation, but its thickness was different at the a-Si/Ni and Ni/a-Si interfaces of opposite stacking. During annealing, the Ni2Si crystalline phase formed, but, surprisingly, we observed that the thicker Ni2Si layer grew faster than the thinner one. Similar peculiar behaviour was observed for the a-Si/Co/a-Si system. To clarify this situation, computer simulations were performed for both systems by using our new conceptual model (Erdélyi et al., 2012). This showed that the chemical thickness of the interfaces and the accelerated diffusion in the intermetallic phase probably play key roles in the earliest stages of growth.

Original languageEnglish
Pages (from-to)111-120
Number of pages10
JournalActa Materialia
Volume87
DOIs
Publication statusPublished - Apr 1 2015

Keywords

  • EXAFS
  • GIXRF
  • Nucleation in a sharp concentration gradient
  • Solid-state reaction
  • XRD

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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