Far infrared reflectivity of liquid Ga–Te alloys

The far infrared (FIR) reflectivities of liquid Ga–Te alloys as a function of composition, temperature, and frequency have been measured using both a far infrared laser and Fourier-transform spectroscopy. The reflectivity R is anomalously enhanced between the compositions GaTe and Ga2Te3, suggesting molecular clustering in this alloy range. The temperature dependence of R appears to correspond to an activated conductivity, and is strongest near Ga2Te3. The variation of R with frequency for the stoichiometric alloys is Drude-like at higher frequencies, but is nearly constant below 175 cm−1 for GaTe. The FIR conductivities extrapolated to zero frequency are significantly larger than the direct current (dc) values. The data are similar to liquid Mg–Bi measurements and to the spectra of several amorphous glasses. The composition dependence of R is consistent with a superposed band model for ionic constituents with some covalent bonding. Agreement of the frequency dependence of R with experimental values requires a small constant density of states at the Fermi energy.