Impact of Sulfur Concentration on the Magnetic and Electrical Characteristics of ZnMnO Thin Films

• Published in: East European journal of physics 2024-12 (4), p.284-288
• Main Authors: Arslanov, Azamat O., Yuldashev, Shavkat U., Kwon, Younghae, Il-Ho, Ahn
• Format: Article
• Language: English
• Subjects: Diluted magnetic semiconductors; Isovalent anion alloying; Mn-doped p-type ZnO; Resistivity anomaly; Sulfur-doped ZnMnO; ZnO-ZnS alloy
• ISSN: 2312-4334; 2312-4539
• DOI: 10.26565/2312-4334-2024-4-30

Influence of the sulfur doping on the structural, optical, electrical and magnetic properties of ZnMnO thin films fabricated using the ultrasonic spray pyrolysis technique was investigated. Our study reveals that increasing sulfur content leads to a noticeable shift in the band gap energy towards the red spectrum, an indicator of altered electronic states and potential for enhanced spintronic functionalities. The strong reduction in the band gap for the sulfur doped ZnMnO alloys is the result of the upward shift of the valence-band edge. As a result, the room temperature bandgap of ZnMnO1-xSx alloys can be tuned from 3.2 eV to 2.97 eV for x ≤ 0.2. The observed large bowing in the composition dependence of the energy bandgap arises from the anticrossing interactions between the valence-band of ZnO and the localized sulfur level above the ZnMnO valence-band maximum. The doping process significantly modifies the ferromagnetic properties, with an observed increase in Curie temperature correlating with higher sulfur concentrations. These changes are attributed to the increased free holes concentration, which facilitates a more robust exchange interaction between the magnetic ions. Additionally, the structural assessments via scanning electron microscopy confirm the uniform integration of sulfur into the ZnMnO matrix, resulting in distinct nanocrystalline formations. This study contributes to the understanding of doping mechanisms in semiconductor materials, especially for highly mismatched alloys, where the anions are partially substituted with isovalent atoms of considerably different size and/or electronegativity, offering insights into the tunability of their magnetic and electronic properties for potential future applications in spintronic devices.