Modeling of Structural Properties and Transport Phenomena in Doped Multicomponent 2D Semiconductors

Using density functional theory (DFT), the electronic structure, lattice parameters, magnetic and thermodynamic properties of TlIn_1–xCr_xS₂ with a monoclinic system were calculated. The influence of the degree of doping with chromium impurities on the properties of TlIn_1–xCr_xS₂ supercells has been studied. Calculations were carried out using ab initio methods in the local electron density approximation (LDA) and in the generalized gradient approximation (GGA). Spin-orbit and Coulomb interactions were taken into account in DFT calculations. A change in the concentration of chromium impurity (x = 0.001–0.02) in TlInS₂ does not lead to a change in the equilibrium lattice parameters and the type of magnetic ordering in TlIn_1–xCr_xS₂. Phase equilibria and stability of binary and ternary compounds were studied by the thermodynamic method and the functional DFT GGA method in the Tl–In–S ternary system. The constructed isothermal section of the phase diagram at 298 K confirms the insignificant region of homogeneity, based on intermediate ternary compounds, of the Tl–In–S system.The formation energies of the compounds TlInS₂ and TlIn_1–xCr_xS₂ (x = 0.001–0.02) were calculated by the DFT method and are thermodynamically consistent with each other. The energy of formation of the TlInS₂ compound, calculated by theoretical methods, is also consistent with experimental data. This indicates the adequacy of the calculation models used. In order to determine stable doping conditions, we analyzed the thermodynamic properties of the phases of the Tl–In–S system, established stable states of multicomponent phases, stable equilibria between binary and ternary compounds of the TlIn_1–xCr_xS₂ system. Polycrystals were synthesized and TlIn_1–xCr_xS₂ single crystals with different chromium impurity concentrations (x = 0, 0.001 and 0.02) were grown from them. The crystal structure, thermodynamic, dielectric, electrical and dosimetric characteristics of TlIn_1–xCr_xS₂ single crystals were studied. The calculated thermodynamic and physical properties of the TlIn_1–xCr_xS₂ phases are compared with experimental data.