| 1. |
- Eklund, Per, et al.
(författare)
-
Homoepitaxial growth of Ti-Si-C MAX-phase thin films on bulk Ti3SiC2 substrates
- 2007
-
Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 304:1, s. 264-269
-
Tidskriftsartikel (refereegranskat)abstract
- Ti3SiC2 films were grown on polycrystalline Ti3SiC2 bulk substrates using DC magnetron sputtering. The crystallographic orientation of the film grains is shown to be determined by the respective substrate-grain orientation through homoepitaxial MAX-phase growth. For a film composition close to Ti:Si:C=3:1:2, the films predominantly consist of MAX phases, both Ti3SiC2 and the metastable Ti4SiC3. Lower Si content resulted in growth of TiC with Ti3SiC2 as a minority phase. Thus, MAX-phase heterostructures with preferred crystallographic relationships can also be realized.
|
|
| 2. |
- Haddad, Noël, et al.
(författare)
-
Dielectric properties of Ti2AlC and Ti2AlN MAX phases : The conductivity anisotropy
- 2008
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 104:2
-
Tidskriftsartikel (refereegranskat)abstract
- The optical properties of Ti2AlN and Ti2AlC were determined in the 2-80 eV energy range by electron energy loss spectroscopy and in the visible-ultraviolet range, from 1.6 to 5.5 eV, by spectroscopic ellipsometry. Both experimental techniques are angular resolved and in very good agreement over their overlapping energy range. We observe a dependence of the dielectric function as a function of the crystallographic orientation of the crystals. In particular, we notice a shift of the energy position of the plasmon absorption of Ti2AlC with respect to Ti2AlN. Moreover, a drastic change is also observed in the shape of the dielectric function as a function of the composition (or valence electron concentration). The dielectric functions are fitted to an empirical semiclassic Drude-Lorentz model to obtain physical parameters such as the relaxation times. These microscopic parameters are then used in a macroscopic model to yield the transport properties such as the static conductivity as function of the crystal orientation. Ti 2AlN is found to be a better conductor than Ti2AlC in all orientations, which is consistent with experimental measurements. A comparison of the electrical and optical properties of these two compounds is made in terms of different electronic properties and interband-intraband transitions deduced from our model. © 2008 American Institute of Physics.
|
|
| 3. |
- Mendoza-Galvan, Arturo, et al.
(författare)
-
Spectroscopic Ellipsometry of Bulk MAX-phases
- 2009
-
Ingår i: Proceedings of the AVS 56th International Symposium & Exhibition, 2009.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- MAX-phases are compounds with the chemical formula Mn+1AXn where M is a transition metal, A is an element from column 13 to 16 in the periodic system and X represents C or N and n = 1, 2 or 3. These materials are potentially technologically important as they show unique refractory and other physical properties due to the combination of metals and ceramics. From a fundamental point of view the band structure of these materials are of interest and optical reference data are important to determine. Herein we report, for the first time, on the optical properties of NbTiAlC, Nb2AlC, TiSC2, Cr2GeC, TiGeC2, Ti2AlC, and Ti2AlN by spectroscopic ellipsometry in the 0.03 to 6.0 eV spectral range. The ellipsometric data in the infrared range show features corresponding to Fano modes indicating the presence of a thin oxide layer a few nm thick. The optical response of these MAX-phases is represented by a Drude-Lorentz model. Thus, in the low energy range the electrical conductivity through the Drude term is evaluated and two or three interband electronic transitions which are compositional dependent can be identified at photon energies in the visible-ultraviolet range 1.0-6.0 eV.
|
|
