Fabrication of high coercivity magnetic nanostructures by electron beam induced deposition with dual metal-organic gases

我们将我们的UHV-FE-SEM，通过引入一种气体在其腔室，EBID仪器与双气体引入系统。利用该装置，以Fe（C_5H_5）_2和Fe（CO）_5为混合气体进行电子束诱导沉积，制备了不同铁浓度的纳米结构。结果表明，通过改变Fe（C_5H_5）_2和Fe（CO）_5的分压比，可以控制反应体系中的铁浓度。采用电子全息技术测量了不同铁碳比的纳米结构的剩余磁通密度Br，结果表明Br值与铁的浓度有关;以Fe（CO）5和（CH 3）3（C5 H5）Pt的混合气体为前驱体，在600℃下退火2 h，完成了纳米结构的晶化过程。纳米棒由封装在含碳鞘内的结晶Fe-Pt合金纳米颗粒链组成。通过电子衍射和高分辨透射电子显微镜（HRTEM）证实了纳米粒子为面心四方FePt相L10。通过电子全息图测量了纳米棒的剩余磁通密度Br，结果表明纳米棒具有较强的铁磁性，水蒸气的加入可以有效地降低Fe（CO）5中的碳含量，加入足够的水蒸气可以形成无碳的晶态Fe 3 O 4纳米棒。而在W（CO）_6的情况下，所得的纳米棒由富碳的无定形基体和嵌入在基体中的氧化钨纳米晶体组成。这一结果表明，铁的催化性能对使用水蒸气的EBID过程的影响可能是重要的。

We modified our UHV-FE-SEM, by which we could introduce one kind of gas in its camber, to an EBID instrument with dual gases introduction system. Electron beam induced deposition with a mixture gas of Fe (C_5H_5)2 and Fe (CO)_5 was carried out to fabricate nanostructures with different iron concentrations using this instrument. It was found that the iron concentration could be controlled by changing the ratio of partial pressure of Fe (C_5H_5)_2 and Fe (CO)_5. Electron holography was employed to evaluate the remanent magnetic flux density Br for the nanostructures with various compositional ratios of iron to carbon, indicating that the Br value is related to the iron concentration.A mixture gas of Fe (CO)_5 and (CH_3)_3 (C_5H_5)Pt was used as a precursor and post-annealing at 600℃ for 2 hour was performed to accomplish the crystallization process. Nanorods were composed of a chain of crystalline Fe-Pt alloy nanoparticles encapsulated within a carbon-containing sheath. The nanoparticles were identified to be face centered tetragonal FePt phase L10 by electron diffraction and HRTEM. The residual magnetic flux density Br of the nanorods was evaluated from electron holography, showing a strong ferromagnetic character.The addition of water vapor to Fe (CO)_5 could effectively reduce carbon content and the addition of enough water vapor resulted in the formation of carbon-free crystalline Fe_3O_4 nanorods. However, in the case of W (CO)_6, the resulting nanorods were composed of a carbon-rich amorphous matrix and tungsten oxide nanocrystals embedded in a matrix. This result suggested that the effect of the catalytic property of iron on the EBID process with water vapor use might be important.