研究目的
To investigate the structural, Hall effect, electronic transport, and magnetic properties of n-type diluted magnetic semiconductors Ge0.96?xBixFe0.04Te thin films, focusing on the transformation from p-type to n-type carriers with Bi substitution and the establishment of ferromagnetism dependent on carrier transmissions.
研究成果
The study successfully fabricated n-type diluted magnetic semiconductors Ge0.96?xBixFe0.04Te thin films with high-quality epitaxy. Bi substitution transformed carriers from holes to electrons, and ferromagnetism was established only in high Bi-doping samples, dependent on carrier concentrations and transmissions. First-principles calculations supported the existence of ferromagnetic states, suggesting potential for applications in microelectronics and magnetic storage, with recommendations for further investigations on doping limitations.
研究不足
The increase in Bi-doping concentration is limited as higher concentrations (e.g., Ge0.52Bi0.44Fe0.04Te) lead to second-phase formation instead of single-phase films, indicating constraints in doping levels for maintaining film quality and ferromagnetism.
1：Experimental Design and Method Selection:
The study used pulsed laser deposition (PLD) to fabricate Ge0.96?xBixFe0.04Te thin films on BaF2 (111) substrates, with structural analysis via X-ray diffraction (XRD) and atomic force microscopy (AFM), Hall effect and resistivity measurements using a Physical Property Measurement System (PPMS), and magnetization measurements with a SQUID magnetometer. First-principles calculations were performed using density functional theory with VASP software.
2：96?xBixFe04Te thin films on BaF2 (111) substrates, with structural analysis via X-ray diffraction (XRD) and atomic force microscopy (AFM), Hall effect and resistivity measurements using a Physical Property Measurement System (PPMS), and magnetization measurements with a SQUID magnetometer. First-principles calculations were performed using density functional theory with VASP software.
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: Thin films with varying Bi doping concentrations (e.g., Ge0.64Bi0.32Fe0.04Te, Ge0.76Bi0.2Fe0.04Te) were prepared, selected based on doping levels to study carrier type and magnetic properties.
3：64Bi32Fe04Te, Ge76Bi2Fe04Te) were prepared, selected based on doping levels to study carrier type and magnetic properties.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment includes PLD system, XRD, AFM, PPMS, SQUID magnetometer; materials include BaF2 substrates and target materials for film deposition.
4：Experimental Procedures and Operational Workflow:
Films were deposited using PLD, characterized by XRD and AFM for structure and morphology, Hall effect and resistivity measured at different temperatures, magnetization measured under zero-field cooling and field cooling models, and first-principles calculations conducted to model ferromagnetic states.
5：Data Analysis Methods:
Data analyzed using models for carrier transport (e.g., small polaron hopping), and first-principles calculations to determine energy differences between ferromagnetic and antiferromagnetic states.
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