研究目的
To assess the influence of the film growth temperature and molecular oxygen pressure at a constant flow rate of Fe atoms on the properties of magnetite films grown on R-plane single-crystal sapphire substrates via pulsed laser deposition and characterize the films by a variety of techniques in order to find conditions that ensure growth of films suitable for the fabrication of micro- and nanostructures.
研究成果
Epitaxial Fe3O4 films with properties approaching reference values can be produced on R-plane sapphire having a 5-nm-thick epitaxially grown MgO seed layer. The contradiction between the growth conditions needed to optimize the electrical properties of Fe3O4 films and minimize their surface roughness can be resolved by growing smooth Fe3O4 films at a low temperature and then annealing them at an optimal temperature slightly below the temperature at which the films begin to react with MgO.
研究不足
The study is limited to the growth of Fe3O4 films on R-plane sapphire substrates with and without a MgO seed layer. The interaction between the growing film and MgO seed layer at temperatures above 440°C may degrade the properties of the films.
1：Experimental Design and Method Selection:
Pulsed laser deposition was used to grow epitaxial Fe3O4 films on R-plane single-crystal sapphire substrates with and without a MgO seed layer. The influence of growth temperature and molecular oxygen pressure on the properties of the films was studied.
2：Sample Selection and Data Sources:
R-plane single-crystal sapphire (Al2O3 ( 012)) wafers 6 × 5 mm2 in area were used as substrates. A 5-nm-thick MgO (001) seed layer was grown via evaporation of a high-purity Mg target in a molecular oxygen atmosphere.
3：List of Experimental Equipment and Materials:
Ultrahigh-vacuum chamber, pulsed laser evaporation system, high-purity (99.99%) Fe target, molecular oxygen, R-plane single-crystal sapphire substrates, Mg target for seed layer deposition.
4：99%) Fe target, molecular oxygen, R-plane single-crystal sapphire substrates, Mg target for seed layer deposition.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Films were grown under a residual vacuum of about 10–10 Torr at different molecular oxygen partial pressures and a constant flow rate of metal atoms (about 20 nm/min). The crystal structure of the films was studied by X-ray diffraction. Their surface morphology was examined by atomic force microscopy (AFM). Electrical measurements were conducted by the four probe technique.
5：Data Analysis Methods:
The AFM measurement results were used to assess the root-mean-square surface roughness of the films. The temperature derivative of the resistivity as a function of temperature was used to find parameters of the Verwey transition.
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