Dielectric and Optical Properties of Sm-Doped TlInS2 Single Crystals

Semiconductor compounds TlIn1 – xSmxS2 (x = 0, 0.001, 0.005) were synthesized, and high-quality single crystals were grown. X-ray diffraction analysis confirmed that all samples possess a stable monoclinic crystal structure belonging to the C2/c space group. The dielectric properties of TlIn1 – xSmxS2 single crystals were investigated at room temperature in the frequency range of 20 Hz to 1 MHz. The frequency dependence of the real and imaginary parts of the dielectric permittivity, dielectric losses, and AC conductivity was analysed. Parameters of localized states were calculated using the Mott model, revealing that, compared to pure TlInS2, the Sm-doped samples exhibited increased AC conductivity, a higher density of localized states near the Fermi level, and longer average hopping distances and times. Additionally, optical absorption measurements were conducted in the temperature range of 100–300 K, and the bandgap energy was determined using the Tauc method.