Proposition of new stable rare-earth ternary semiconductor sulfides of type LaTlS2 (La= Er, Eu, Tb): Ab-initio study and prospects for optoelectronic, spintronic and thermoelectric applications.

Based on ab-initio calculations in the framework of the density functional theory (DFT), an analysis of the structural, magnetic, thermoelectric, and optoelectronic properties of three newly designed ternary semiconductor sulfides: LaTlS 2 (La = Er, Eu, Tb) is carried out. It has been established that these compounds are thermodynamically and mechanically stable. Indirect bandgaps are found with the values 1.53, 1.62, 1.70 eV for the spin up (↑) channel for ErTlS 2, EuTlS 2, TbTlS 2, respectively. For the spin down (↓) channel, the obtained values are slightly lower. The paramagnetic magnetic moments are predicted by observing different band shapes in the energy band structures for the spin up (↑) and spin down (↓) states. The values of the magnetic moments for ErTlS 2 , EuTlS 2 and TbTlS 2 are large, being respectively: 3.00, 6.00 and 6.00 μ B. The R (ω) spectra show a very low reflectance in the IR and visible regions, however, up to 45% of the photon reflection occurs in the UV region. The spectra of the Seebeck coefficient show that EuTlS 2 is initially p-type semiconductor, but becomes n-type semiconductor above 350 K. Whereas ErTlS 2 and TbTlS 2 are initially n-type semiconductors, but become p-type semiconductors at temperatures higher than 100 K. [ABSTRACT FROM AUTHOR]