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Ordered CaSi 2 Microwall Arrays on Si Substrates Induced by the Kirkendall Effect
Author(s) -
Meng Xiang,
Ueki Akiko,
Tatsuoka Hirokazu,
Itahara Hiroshi
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201605133
Subject(s) - kirkendall effect , materials science , microstructure , substrate (aquarium) , epitaxy , deposition (geology) , phase (matter) , crystal (programming language) , plane (geometry) , crystallography , composite material , geometry , chemistry , metallurgy , geology , layer (electronics) , paleontology , oceanography , mathematics , organic chemistry , sediment , computer science , programming language
We have specified the synthetic conditions to obtain one‐directionally ordered CaSi 2 microwall arrays vertically grown on a Si substrate. Our basic concept is based on the utilization of the Kirkendall effect for reactive deposition epitaxy (RDE). We found for the first time that: 1) a much larger Ca vapor supply on the Si substrate than the conventional RDE, 2) the adoption of a two‐step heating process, and 3) the selection of the crystal axis of the Si surface are the keys to control the microstructures of CaSi 2 on the Si substrate. The CaSi phase was first formed on Si, then the CaSi 2 phase was formed at the CaSi/Si interface. Based on the Kirkendall effect, the interdiffusion of Ca and Si was enhanced in the vertical direction rather than in the parallel direction to the Si surface. CaSi 2 tends to grow along four equivalent Si{111} planes, however, the specific orientation of the Si surface resulted in CaSi 2 microwalls grown along its Si(11 1 ‾ ) plane, the only plane directing nearly vertical to the surface among the Si{111} planes. These results suggest that the Kirkendall effect under asymmetric growth of target materials would be a rational strategy to obtain their ordered microstructures.