Features of IR reflection spectra of β-Tl1-xCuxInS2 single crystals (0 ≤ X ≤ 0.015)

Abstract

The method of long-wave spectroscopy made it possible to study the IR reflection spectra of layered single crystals β-Tl1-xCuxInS2 (0≤X≤0.015) in in the frequency range of 40-500 cm−1 and the temperature range of 84 ¸ 300 K. It was shown that partial substitution of thallium atoms with copper atoms leads to a decrease in the frequencies of the corresponding oscillations in the frequency range of 40-500 cm−1 and does not lead (at these concentrations) to local oscillations. It was found that solid solutions β-Tl1-xCuxInS2 (X=0 ÷ 0.015) exhibit the characteristic single-mode behavior. It was shown that partial substitution of thallium atoms with copper atoms in single crystals β-Tl1-xCuxInS2 (X = 0.005; 0.010; 0.015) weakens the ionic bond in Tl–S, as a result of which the frequencies of “internal” oscillations shift towards low temperatures.