Study of the electronic structure, magnetic and superconducting properties of Zn(1−x) (Fe, V)xSeyTe(1−y) materials using computational and experimental method

Abstract

The quaternary compound Zn(1−x) (Fe, V)xSeyTe(1−y) is a transition metal chalcogenide with fascinating properties that can be employed in electronics, energy storage, spintronics, and magneto-optical devices. The need for alloying and doping these types of materials is largely for further optimization for better and more specialized applications. The electronic structure, magnetic, vibrational, and superconducting properties of the Zn(1−x) (Fe, V)xSeyTe(1−y) materials and their fragments are investigated using both computational and experimental methods. In the computational approach, both DFT and DFT+U approximations were considered. For this study, the quantum espresso and electron-phonon wannier (EPW) programs were employed. The second section of this dissertation focuses on synthesizing the iron-doped ZnSe (i.e., Zn(1−x)FexSe) thin films by the chemical bath deposition method to understand how structural, electrical, and optical features are affected by iron doping. This study revealed that the DFT+U calculation enhances the electrical properties more than the DFT approximation. When the iron concentration in Zn(1−x)FexSe is less than 12.5%, half-metallic qualities are observed, while greater concentrations are in spin glass states, which is compatible with the experimental observations reported. However, vanadium doping demonstrated that the Zn(1−x)VxSe can behave as a dilute magnetic material even at room temperature, with potential applications in spintronics and magneto-optical devices. Remarkably, the doping of iron and vanadium in ZnSe results in considerable changes to the system’s structural, electrical, and magnetic properties. Furthermore, while theoretically it is conceivable to generate n-type iron and vanadium-co-doped ZnTe semiconductors, obtaining n-type ZnTe semiconductors has remained disputed. The iron selenide-based superconductors are one of four families of iron-based superconductors that exhibit enhancements in magnetic and superconducting properties over time. However, the anisotropic and isotropic superconducting behavior of FeSe remains challenging. In this case, the isotropic behavior of the tetragonal FeSe superconductor was investigated. It revealed that the superconductivity critical temperature enhancement up to 26 K is theoretically possible under room conditions. Also, the experimental results indicate that the determined lattice constant and band gap of the iron-doped system are decreasing as the iron concentration increases. This is consistent with the DFT result, except that the band gap of the DFT result lags behind due to discontinuities in the functional used.