Advanced Physical Research

This study investigates the growth, structural, and optical properties of Pb_1-xMnₓTe and Pb_1-xEuₓTe epitaxial films grown on freshly cleaved BaF₂ (111) substrates by molecular beam epitaxy under a vacuum of 10^-4 Pa with an additional Te vapor source. The optimal growth conditions were determined as substrate temperature T_sub=573–640 K, source temperature T_sour=1123–1173 K and condensation rate J_c=8¸12 Å/sеc Optical absorption spectroscopy and X-ray diffraction analyses confirmed the formation of single-phase epitaxial films with high crystalline quality. For x=0.05, the lattice constants were approximately 6.43 Å for Pb_1-xMnₓTe and 6.476 Å for Pb_1-xEuₓTe. Optical measurements showed that increasing Mn²⁺ and Eu²⁺ concentrations leads to band-gap widening. Specifically, the optical band gap at 77 K increases from about 0.21 eV for pure PbTe to approximately 0.44 eV for Pb₁₋ₓMnₓTe and 0.53 eV for Pb₁₋ₓEuₓTe, exceeding 0.5 eV at europium contents x > 0.09. This effect is associated with modifications of the electronic band structure caused by Mn(Eu) substitution in the Pb sublattice, exchange interactions, lattice effects, and the interaction of localized Mn 3d and Eu 4f states with band-edge states. Additionally, the influence of γ-irradiation on the structural properties of the films was investigated. These findings show that compositional engineering of Pb₁₋ₓMnₓTe and Pb₁₋ₓEuₓTe epitaxial films enables controllable tuning of the band gap in the mid-infrared range, making them promising candidates for infrared optoelectronic, thermoelectric, and spintronic device applications.