M{sub n+1}AX{sub n} phases in the Ti-Si-C system studied by thin-film synthesis and ab initio calculations

Journal Article · Fri Oct 15 04:00:00 EDT 2004 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.70.165401· OSTI ID:20664932

Palmquist, J -P; Wilhelmsson, O; Jansson, U ^[1]; Li, S; Katsnelson, M I; Johansson, B; Ahuja, R; Eriksson, O ^[2]; Persson, P O.A.; Emmerlich, J; Hoegberg, H; Hultman, L ^[3]

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1. Uppsala University, Department of Materials Chemistry, Angstroem Laboratory, P.O. Box 538 SE-751 21 Uppsala (Sweden)
2. Uppsala University, Department of Physics, Angstroem Laboratory, P.O. Box 530 SE-751 21 Uppsala (Sweden)
3. Linkoeping University, Department of Physics, IFM, Thin Film Physics Division, SE-581 83 Linkoeping (Sweden)

Thin films of M{sub n+1}AX{sub n} layered compounds in the Ti-Si-C system were deposited on MgO(111) and Al{sub 2}O{sub 3}(0001) substrates held at 900 deg. C using dc magnetron sputtering from elemental targets of Ti, Si, and C. We report on single-crystal and epitaxial deposition of Ti{sub 3}SiC{sub 2} (the previously reported MAX phase in the Ti-Si-C system), a previously unknown MAX phase Ti{sub 4}SiC{sub 3} and another type of structure having the stoichiometry of Ti{sub 5}Si{sub 2}C{sub 3} and Ti{sub 7}Si{sub 2}C{sub 5}. The latter two structures can be viewed as an intergrowth of 2 and 3 or 3 and 4 M layers between each A layer. In addition, epitaxial films of Ti{sub 5}Si{sub 3}C{sub x} were deposited and Ti{sub 5}Si{sub 4} is also observed. First-principles calculations, based on density functional theory (DFT) of Ti{sub n+1}SiC{sub n} for n=1,2,3,4 and the observed intergrown Ti{sub 5}Si{sub 2}C{sub 3} and Ti{sub 7}Si{sub 2}C{sub 5} structures show that the calculated difference in cohesive energy between the MAX phases reported here and competing phases (TiC, Ti{sub 3}SiC{sub 2}, TiSi{sub 2}, and Ti{sub 5}Si{sub 3}) are very small. This suggests that the observed Ti{sub 5}Si{sub 2}C{sub 3} and Ti{sub 7}Si{sub 2}C{sub 5} structures at least should be considered as metastable phases. The calculations show that the energy required for insertion of a Si layer in the TiC matrix is independent of how close the Si layers are stacked. Hardness and electrical properties can be related to the number of Si layers per Ti layer. This opens up for designed thin film structures the possibility to tune properties.

• OSTI ID: 20664932
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 16 Vol. 70; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALUMINIUM OXIDES
BINDING ENERGY
DENSITY FUNCTIONAL METHOD
ELECTRICAL PROPERTIES
FERMI LEVEL
HARDNESS
LAYERS
MAGNESIUM OXIDES
MAGNETRONS
MONOCRYSTALS
SILICON COMPOUNDS
SPUTTERING
STOICHIOMETRY
SURFACE COATING
SYNTHESIS
THIN FILMS
TITANIUM CARBIDES
TRANSMISSION ELECTRON MICROSCOPY
VAPOR PHASE EPITAXY
X-RAY DIFFRACTION