Aharonovich Igor, Tamir Shoshana, Lifshitz Yeshayahu
Faculty of Materials Engineering and the Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa 32000, Israel.
Nanotechnology. 2008 Feb 13;19(6):065608. doi: 10.1088/0957-4484/19/6/065608. Epub 2008 Jan 23.
Amorphous SiO(x) nanowires (NWs) were synthesized using laser ablation of silicon-containing targets. The influence of various parameters such as target composition, substrate type, substrate temperature and carrier gas on the growth process was studied. The NWs were characterized using high resolution scanning and transmission electron microscopes (HRSEM and HRTEM) with their attachments: electron dispersive spectroscopy (EDS) and energy electron loss spectroscopy (EELS). A metal catalyst was found essential for the NW growth. A growth temperature higher than 1000 °C was necessary for the NW formation using an Ar-based carrier gas at 500 Torr. The use of Ar-5%H(2) instead of pure Ar resulted in a higher yield and longer NWs. Application of a diffusion barrier on top of the Si substrate guaranteed the availability of metal catalyst droplets on the surface, essential for the NW growth. Ni was found to be a better catalyst than Au in terms of the NW yield and length. Two alternative sequences for the evolution of the amorphous SiO(x) NWs were considered: (a) the formation of Si NWs first and their complete oxidation afterwards, which seems to be doubtful, (b) the direct formation of SiO(x) NWs, which is more likely to occur. The direct formation mechanism was proposed to advance in three stages: preferential adsorption of SiO(x) clusters on the catalyst surface first, a successive surface diffusion to the catalyst droplet lower hemisphere, and finally the formation and growth of the NW between the catalyst and the substrate.
采用含硅靶材的激光烧蚀法合成了非晶态SiO(x)纳米线（NWs）。研究了靶材成分、衬底类型、衬底温度和载气等各种参数对生长过程的影响。使用配备电子色散光谱（EDS）和能量电子损失光谱（EELS）附件的高分辨率扫描和透射电子显微镜（HRSEM和HRTEM）对纳米线进行了表征。发现金属催化剂对纳米线生长至关重要。在500托的氩基载气条件下，纳米线形成需要高于1000°C的生长温度。使用Ar-5%H(2)代替纯氩可提高产量并得到更长的纳米线。在硅衬底顶部施加扩散阻挡层可确保表面有金属催化剂液滴，这对纳米线生长至关重要。就纳米线产量和长度而言，发现镍是比金更好的催化剂。考虑了非晶态SiO(x)纳米线演化的两种替代顺序：（a）首先形成硅纳米线，然后将其完全氧化，这似乎值得怀疑；（b）直接形成SiO(x)纳米线，这更有可能发生。提出直接形成机制分三个阶段进行：首先是SiO(x)团簇在催化剂表面的优先吸附，接着是向催化剂液滴下半球的连续表面扩散，最后是在催化剂和衬底之间形成并生长纳米线。
