Wüest M. 51 Wykes M. 82 Yamaguchi M. 17 Ybarra G. 129 Yubero F ...

JUNE 28 WEDNESDAY MORNING
WeM-Pl.3 FUNCTIONAL CERAMIC THIN FILMS, NEW MATERIALS FOR THE
FUTURE, FROM NATURALLY NANOLAMINATED MAX-PHASES TO TAILORED
NANOCOMPOSITES OF CARBIDES, OXIDES AND NITRIDES. H. Högberg, Thin Film
Physics Division, Department of Physics (IFM), Linköping University, SE-58183 Linköping, Sweden.
There is a strong desire to design a material with properties that match the demands foreseen in future
applications. Thus, the development of functional materials is gaining increased attention in materials
science today. This presentation focuses on two such highly promising branches of functional
thin films, namely the layered ternary ceramic compounds known as the M n+1 AX n (n=1-3) phases,
where M is an early transition metal (Ti, Nb), A is a group 13-15 element (Al, Si, Ge), and (X) is either
C or N, and nanocomposites from the TiC/SiC, TiN/SiN x and ZrO 2 /Al 2 O 3 systems. A limited
miscibility for one of the constituents is inherent to all of these systems, which causes segregation of
the element during synthesis. For the MAX phases, typically synthesized as bulk materials at temperatures
of ∼1300 o C, the process yields an anisotropic crystal structure in which MX blocks are interleaved
by pure A-element layers. This nanolaminated structure give rise to the unique set of properties
for these materials as reported by Barsoum et al. Typically the MAX phases show high oxidation
resistance in combination with good thermal and electrical conductivities. These attributes are
also ideal for advanced thin film applications were multi-functionality is required at elevated temperatures
and/or harsh environment. Recently, we have developed dc magnetron sputtering processes
for the growth of MAX-phase thin films from the systems Ti-A-C, A=Al, Si, Ge, or Sn, using either
growth from elemental sources or Ti 3 SiC 2 and Ti 2 AlC (MAXTHAL®) targets. The processes enables
the growth of epitaxial thin films on Al 2 O 3 (0001) substrates at substrate temperatures in the region
700-1000 o C, including known bulk phases such as Ti 2 GeC, Ti 2 SnC, Ti 3 SiC 2 , and Ti 3 GeC 2 as
well as new phases Ti 4 SiC 3 , Ti 4 GeC 3 , and Ti 3 SnC 2 . Characterization with four-point probe resistivity
measurements shows that our thin films are good conductors. Nanoindentation confirms the ductile
deformation behavior of the MAX phases and reveals details on the formation of pile up.
For the nanocomposite thin films from particularly the TiN/SiN x system the pioneering work by
Vepřek et al has provided invaluable knowledge regarding the microstructure design of films with
improved properties. Their studies show that increased hardness is only achieved when the secondary
amorphous phase (SiN x ) form a 1-2 monolayer thick tissue around small (