Fabrication of Alpha-Iron and Iron Carbide Nanostructures by Electron-Beam Induced Chemical Vapor Deposition and Postdeposition Heat Treatment

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We succeeded in fabricating crystalline alpha-iron nanostructures with desired shapes. Electron-beam-induced chemical vapor deposition with iron carbonyl gas, Fe(CO) 5 , was carried out at room temperature in a field-emission-gun scanning electron microscope to fabricate nanodots, nanorods and square frames. The as-deposited structures exhibited an amorphous phase containing iron, carbon and oxygen in their entire volumes and iron oxide nanocrystals existed near their surfaces. Postdeposition heat treatment at about 600°C resulted in the formation of crystalline alpha-iron and iron carbide phases in their structures, while maintaining their shapes. Quantitative elemental analyses using electron energy loss spectroscopy suggested that the original as-deposited iron-to-carbon compositional ratio is crucial in determining the stoichiometry of the produced structures after the heat treatment.