Synthesis and characterization of dilute magnetic semiconductor based on Zn1−xMnxO thin films prepared by 5-methyl-7-methoxyisoflavone modified sol-gel/spin-coating technique

Abstract

Zn1−xMnxO2 (0.01≤x≤0.09) thin films were prepared by 5-methyl-7-methoxyisoflavone modified sol-gel/spin-coating technique on Quartz substrates to improve their optical properties and room temperature ferromagnetism for spintronic applications. The crystal structure, chemical composition, magnetic and optical properties of these films were investigated by X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, vibrating magnetometer and spectrophotometry. The incorporation of Mn ions into the hexagonal crystal structure of ZnO gave rise to an increase of the unit cell volume and a decrease of the crystal residual stress. However, the introduction of the Mn2+ ions into the ZnO nanocrystals lead to a decrease of the band energy gap from 3.23eV to 2.63eV. The films showed an average optical transparency of 88%. The XPS spectra revealed that 80% of the incorporated Mn ions into the ZnO crystal structure are in the form of Mn2+ and 20% in the form of Mn4+. The replacement of Zn+2 ions by Mn2+ ions resulted in an increase of the amount of the surface oxygen vacancy. The magnetization was improved by more than 50 times compared conventional methods. Therefore, remarkable room temperature ferromagnetism with high saturation magnetic moment (3.32μB/Mn) and high coercivity (280G) were obtained.