| Abstrakt: |
The averaged complex dielectric function [variant_greek_epsilon]=(2[variant_greek_epsilon]⊥+[variant_greek_epsilon]∥)/3 of polycrystalline Ti2AlN, Ti2AlC, Nb2AlC, (Ti0.5,Nb0.5)2AlC, and Ti3GeC2 was determined by spectroscopic ellipsometry covering the mid infrared to the ultraviolet spectral range. The dielectric functions [variant_greek_epsilon]⊥ and [variant_greek_epsilon]∥ correspond to the perpendicular and parallel dielectric tensor components relative to the crystallographic c-axis of these hexagonal compounds. The optical response is represented by a dispersion model with Drude-Lorentz and critical point contributions. In the low energy range the electrical resistivity is obtained from the Drude term and ranges from 0.48 μΩ m for Ti3GeC2 to 1.59 μΩ m for (Ti0.5,Nb0.5)2AlC. Furthermore, several compositional dependent interband electronic transitions can be identified. For the most important ones, Im([variant_greek_epsilon]) shows maxima at: 0.78, 1.23, 2.04, 2.48, and 3.78 eV for Ti2AlN; 0.38, 1.8, 2.6, and 3.64 eV for Ti2AlC; 0.3, 0.92, and 2.8 eV in Nb2AlC; 0.45, 0.98, and 2.58 eV in (Ti0.5,Nb0.5)2AlC; and 0.8, 1.85, 2.25, and 3.02 eV in Ti3GeC2. [ABSTRACT FROM AUTHOR] |
