Effect of Gamma Irradiation on Structural and Optical Properties of CdMnTe Epitaxial Thin Films

Abstract

Cd1-0.06Mn0.06Te epitaxial thin films were synthesis on glass substrates by the Molecular Beam Condensation (MBC) method in the vacuum evaporation equipment УВН-71-ПЗ with steam-oil pumping and nitrogen trap at working pressure of residual gas (1÷2)x10-4 Pa. By using additional source of Te vapor and controlling temperature, it has been determined the optimum conditions for obtaining Cd1-0.06Mn0.06Te epitaxial films with a perfect structure, clean and smooth surface, without of second phase inclusions. XRD investigations showed that Cd1-0.06Mn0.06Te epitaxial films grow on glass substrates on the (111) plane of the face-centered cubic lattice with the lattice parameter of a = 6.481 Å. Effect of γ-irradiation on XRD spectra of Cd1-0.06Mn0.06Te epitaxial films reveals that, XRD patterns of initial and γ-irradiated samples did not show any phase transformations, however there is a variation in relative intensities of diffraction peaks. It has been found that Cd1-0.06Mn0.06Te epitaxial films with a film thickness of d=15 µm, absorb light up to a wavelength of λ=765 nm and at λ>765 nm the absorption begins to gradually decrease and then the material becomes transparent. The obtained results indicate that Cd1-0.06Mn0.06Te epitaxial films absorb light quanta in the visible and infrared spectral regions. Iirradiation of Cd1-0.06Mn0.06Te epitaxial films with γ rays at low irradiation doses leads to a change in the optical parameters, the profile of the spectrum curves and the intrinsic absorption edge. In additions to experimental studies, a theoretical ab initio calculations of band structure (BS) of ideal and defective semiconductors of Cd1-0.06Mn0.06Te has been also carried out by using Density Functional Theory (DFT) method via Atomistix ToolKit computer program. The band gap energy has been calculated as Eg = 1.6 eV for ferromagnetic (FM) and Eg = 1.7 eV for antiferromagnetic (AFM) state of Cd1-0.06Mn0.06Te compound. The results of theoretical calculations on the band gap energy of ideal and defective Cd1-0.06Mn0.06Te semiconductors are in a good agreement with experimental findings.