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 TlIn1–xCrxS2 with a monoclinic system were calculated. The influence of the degree of doping with chromium impurities on the properties of TlIn1–xCrxS2 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 TlIn1–xCrxS2. 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 TlIn1–xCrxS2 (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 TlIn1–xCrxS2 system. Polycrystals were synthesized and TlIn1–xCrxS2 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 TlIn1–xCrxS2 single crystals were studied. The calculated thermodynamic and physical properties of the TlIn1–xCrxS2 phases are compared with experimental data.