Synthesis Of Metal Fe Magnetic Nanowires By Chemical Vapor Deposition And Their Property Research

Metal magnetic nanowires has many unique physical and chemical properties mainly benefiting from its special microstructure, and their microstructure depends on the preparation technology of nanowire. Among the synthesized methods of nanowires, chemical vapor deposition(CVD) is a kind of preparation process that can obtain a large number of nanowires, and has been partly used in commercial application. However, due to the gasification temperature of the metal material is very high, so the CVD method was generally applied to prepare various kinds of oxides or semiconductor nanowires, no studies have been reported the concerning preparation of metal magnetic nanowires by the CVD method. In this paper, we prepared the ferromagnetic nanowires by CVD method using ferrocene as raw material and gold nanoparticles as catalyst, respectively.First of all, as a precursor of nanowires, they must meet the following conditions: low of gasification temperature, the gasification temperature is lower than the decomposition temperature; gasification temperature and decomposition temperature is closed. Through the TG analysis, this paper selects ferrocene(Fe C10H10) as precursors, and the Au nanoparticles as catalyst. The deposition temperature was set at 500°C, 550°C, 600°C, 650°C, 700°C, 750°C; deposition time was set to 1h, 1.5h, 2h, 2.5h; the carrier flow was set to 25 sccm, 50 sccm, 70 sccm, 100sccm; the sapphire and silicon was used the deposition template. The author made a study on the influence of system parameters on the microstructure morphology of fabricated nanowires. Under the optimal conditions including the deposition temperature is 600°C, the deposition time is 2h, and the carrier flow rate is 70 sccm, the sapphire substrate could obtain a large number of Fe nanowires with the diameter of 125 nm and the length of 2um. Through the XRD, SEM, TEM, and other means demonstrated that the obtained nanowire was single crystal of Fe nanowire.Secondly, the growth mechanism of the metal nanowires was discussed, the result reveals that the growth process of nanowires is comprised of four steps: 1. solid ferrocene gasification, gas ferrocene with carrier transport to the deposition chamber, in the deposition chamber the ferrocene decomposed into cyclopentadiene and metallic Fe atom at about 600°C; 2. the decomposition of the Fe atom was adsorbed on the Au nanoparticles, then the Fe-Au alloy was formed; 3. Which Fe-Au alloy as nucleus to adsorbed amount of Fe atoms; 4. The crystal nuclei as the nanowires oriented growth that grown single crystalline Fe nanowires. Through the TEM, EDS can be determined, the growth mechanism of single crystalline Fe nanowires is Vapor-Solid(VS) growth mechanism.Finally, the vibrating sample magnetometer(VSM) were measured hysteresis loops of the nanowires with along the parallel and perpendicular to the direction of nanowires. The test results shown that: the parallel to the nanowire axis is the easy magnetization direction, but the different of two directions anisotropy was not significant. These result due to that the anisotropy of nanowire was mainly composed of shape anisotropy and magnetocrystalline anisotropy, therefore, the magnetization direction in nanowire represents the competition between the shape and crystalline anisotropy competition between the shape and crystalline anisotropy. And the as-prepared nanowire shape anisotropy with Ed=1.8×104 J/m3 to be slightly larger than the magnetocrystalline anisotropy with Ea=1.2×104 J/m3, which resulted the easy axis is along the wire and the small remanent magnetization is 0.37.