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Growth and characterization of MAX-phase thin films
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.ORCID iD: 0000-0002-2837-3656
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
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2005 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 193, no 1-3, 6-10 p.Article in journal (Refereed) Published
Abstract [en]

We report that magnetron sputtering can be applied to synthesize MAX-phase films of several systems including Ti–Si–C, Ti–Ge–C, Ti–Al–C, and Ti–Al–N. In particular, epitaxial films of the known phases Ti3SiC2, Ti3GeC2, Ti2GeC, Ti3AlC2, Ti2AlC, and Ti2AlN as well as the newly discovered thin film phases Ti4SiC3, Ti4GeC3 and intergrown structures can be deposited at 900–1000 °C on Al2O3(0001) and MgO(111) pre-seeded with TiC or Ti(Al)N. From XTEM and AFM we suggest a growth and nucleation model where MAX-phase nucleation is initiated at surface steps or facets on the seed layer and followed by lateral growth. Differences between the growth behavior of the systems with respect to phase distribution and phase stabilities are discussed. Characterization of mechanical properties for Tin+1Si–Cn films with nanoindentation show decreased hardness from about 25 to 15 GPa upon penetration of the basal planes with characteristic large plastic deformation with pile up dependent on the choice of MAX material. This is explained by cohesive delamination of the basal planes and kink band formation, in agreement with the observations made for bulk material. Measurements of the electrical resistivity for Ti–Si–C and Ti–Al–N films with four-point probe technique show values of 30 and 39 μΩ cm, respectively, comparable to bulk materials.

Place, publisher, year, edition, pages
2005. Vol. 193, no 1-3, 6-10 p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-24507DOI: 10.1016/j.surfcoat.2004.08.174Local ID: 6636OAI: oai:DiVA.org:liu-24507DiVA: diva2:244828
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13
In thesis
1. MAX phase thin films: unique multifunctional ceramics with the elements Ti, Si, Ge, Sn, and C
Open this publication in new window or tab >>MAX phase thin films: unique multifunctional ceramics with the elements Ti, Si, Ge, Sn, and C
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Mn+1AXn phases are ternary carbides or nitrides (X) consisting of an early transition metal (M), and (A)- group element (group III-V). They combine ceramic and metallic properties with high oxidation and thermal shock resistance as well as low resistivity. Depending on stoichiometry, they can be classified as 211 (n=1), 312 (n=2), and 413 (n=3) phases. The main purpose of this Thesis is to present the synthesis by epitaxial growth of Tin+1ACn (A: Si, Ge, Sn; n=1-3) thin solid films and to report on the material’s intrinsic mechanical and electrical properties. DC magnetron sputtering of MAX-phase carbides from three individual elemental targets is presented as an original and successful deposition method. The emphasis is on the archetypical Ti3SiC2, but I also demonstrate growth of a wide range of other single-crystal Tin+1ACn thin films, including Ti2GeC, Ti3GeC2, Ti2SnC, previously available only in bulk form, as well as completely new phases of Ti4SiC3, Ti4GeC3, and Ti3SnC2, together with some intergrown 523 (211+312) and 725 (312+413) structures.

A combination of x-ray diffraction (XRD), transmission electron micrcoscopy (TEM) analysis, x-ray photoelectron spectroscopy, elastic recoil detection analysis, and Rutherford backscattering spectrometry of the films reveal single-phase and epitaxial growth of Tin+1SiCn(0001) (n = 2, 3) and Ti2GeC MAX phases at substrate temperatures (TS) above 700 to 1000 °C. For TS = 500 – 700 °C, Si is accommodated at twin boundaries between TiC(111) planes. Depositions at TS = RT – 350 °C yield nc-TiC/SiC nanocomposite films or TiC growth with substitutionally incorporated Si due to kinetic constraints. Vacuum-annealing with in situ XRD measurements of the films between 800 – 1400 °C revealed a thermal stability of up to ~1000 °C. A MAX-phase decomposition model is presented within this Thesis. It starts by Si out-diffusion and evaporation from the surface between ~1000 – 1100 °C and is accompanied by any O uptake and SiO evaporation. Subsequently, the free Ti3C2 slabs relax and undergo detwinning. The decomposition process is ended by TiC0.67 formation by C redistribution and recrystallization with void formation.

The mechanical response to deformation was tested on Ti3SiC2(0001) films using nanoindentation. Small applied normal forces yielding a minimum on plastic deformation reveal hardness values of up to 24 GPa, which decrease with larger indentation depths. Young’s moduli between 320 and 343 GPa were measured. Atomic force microscopy (AFM) surface imaging and Focused Ion Beam cross-sectional TEM studies confirm that mechanical deformation in this ductile ceramic takes place by kink formation and delamination along basal planes, due to edge dislocation pile-ups forming the kink boundaries resulting in local deformation-energy dissipation. Friction measurements yield a friction coefficient (μ) of 0.1 for normal loads of FN = 100-200 μN. μ increases to 0.8 with increased FN up to 0.24 N, as delamination and kinking are introduced accompanied by third-body abrasion as shown by scanning electron microscopy. By comparing electrical resistivity values obtained by four-point probe measurements, it is found that all studied MAX-phase thin film systems exhibit good conduction properties.

Place, publisher, year, edition, pages
Institutionen för fysik, kemi och biologi, 2006. 48 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1024
Keyword
Thin solid films, Single-crystal
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-7449 (URN)91-85523-64-X (ISBN)
Public defence
2006-06-16, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
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Available from: 2006-09-27 Created: 2006-09-27 Last updated: 2012-11-19

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Högberg, HansHultman, LarsEmmerlich, JensJoelsson, TorbjörnEklund, Per

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