TY - JOUR
T1 - Strain in coherent cobalt silicide islands formed by reactive epitaxy
AU - Bennett, Peter
AU - Smith, David
AU - Robinson, I. K.
N1 - Funding Information:
This work was carried out (in part) at the National Synchrotron Light Source, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Division of Materials Sciences and Division of Chemical Sciences. The work was supported also by the National Science Foundation under grants DMR99-81779 (PAB), DMR96-32635 (ASU MRSEC) and DMR98-76610 (IKR).
PY - 2001/8/1
Y1 - 2001/8/1
N2 - We have used surface X-ray diffraction (XRD) to measure strain in coherent islands of cobalt silicide formed by depositing 0-5 ML of cobalt on Si(1 1 1)-7 × 7 at various temperatures. Silicide structure is determined from truncation rod scans, while average island dimensions (width and height) and strain are determined from diffraction lineshapes and verified with TEM. At 800°C, the islands are fully coherent B-type CoSi 2 , approximately 8 nm thick and >300 nm wide, with atomically flat top and bottom surfaces. At 500°C, the islands are CoSi 2 , approximately 6 nm thick and 35 nm wide. The lattice parameter is ∼50% relaxed, primarily due to strain relief at the island edges. At 300°C and coverage of 2 ML, the islands are ∼3 nm high and ∼3 nm wide and show long-range position correlation due to registry with the substrate. At higher coverage, they are ∼4 nm high and ∼40 nm wide and commensurate, but lack long-range correlation. It appears that the silicide formed at 300°C is pseudomorphic Co 2 Si-θ for coverage below 2 ML, but is a mixture of CoSi 2 and metastable CoSi(CsCl) at higher coverage.
AB - We have used surface X-ray diffraction (XRD) to measure strain in coherent islands of cobalt silicide formed by depositing 0-5 ML of cobalt on Si(1 1 1)-7 × 7 at various temperatures. Silicide structure is determined from truncation rod scans, while average island dimensions (width and height) and strain are determined from diffraction lineshapes and verified with TEM. At 800°C, the islands are fully coherent B-type CoSi 2 , approximately 8 nm thick and >300 nm wide, with atomically flat top and bottom surfaces. At 500°C, the islands are CoSi 2 , approximately 6 nm thick and 35 nm wide. The lattice parameter is ∼50% relaxed, primarily due to strain relief at the island edges. At 300°C and coverage of 2 ML, the islands are ∼3 nm high and ∼3 nm wide and show long-range position correlation due to registry with the substrate. At higher coverage, they are ∼4 nm high and ∼40 nm wide and commensurate, but lack long-range correlation. It appears that the silicide formed at 300°C is pseudomorphic Co 2 Si-θ for coverage below 2 ML, but is a mixture of CoSi 2 and metastable CoSi(CsCl) at higher coverage.
KW - Coherent island
KW - Reactive epitaxy
KW - Silicide
KW - Strain
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U2 - 10.1016/S0169-4332(01)00321-X
DO - 10.1016/S0169-4332(01)00321-X
M3 - Article
AN - SCOPUS:0035426472
SN - 0169-4332
VL - 180
SP - 65
EP - 72
JO - Applied Surface Science
JF - Applied Surface Science
IS - 1-2
ER -