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Electron beam induced deposition (EBID) is a promising technique for fabricating nanometer-sized structures in a position- and size-controlled manner. In this technique, organometallic precursors are decomposed by focused electron beams. Then, the non-volatile part of the decomposed precursor deposits on the substrate, and volatile part is pumped out. As electron beams can be focused to a sub-nanometer scale in modern electron microscopes with a field emission gun, the resolution of EBID is now reaching down to subnanometers. However, the deposits obtained by EBID generally consisted of amorphous carbon or nanometer-sized crystals embedded in an amorphous carbon matrix. Most carbon atoms are considered to come from the legands of organometallic molecules used as a precursor. This carbon contamination may be the most serious drawback and is preventing practical uses of EBID in nanodevice technology. Thus, carbon reduction techniques are required. In this study, nanostructures, such as nanowires, were fabricated by EBID using an iron pentacarbonyl precursor in a scanning electron microscope with a custom-made gas introduction system. Several techniques to reduce carbon in the deposits were tried, including post-deposition heat-treatments and the modification of precursor. After the deposition and post-deposition heat-treatment, the nanostructures were observed using a transmission electron microscope (TEM). The compositions of the nanostructures were measured using electron energy loss spectroscopy (EELS). TEM observation, electron diffraction analyses and EELS measurements revealed that the post-deposition heat-treatment in vacuum resulted in a formation of bcc-iron and the heat-treatment in air led to the formation of a mixture of hematite and maghemite iron oxides. Carbon-free magnetite iron oxide was formed by mixing a small amount of water vapor in the iron pentacarbonyl precursor. |