Plastic deformation dominates chemical reactions in Ti/Si multilayered nanofilms
Plastic deformation dominates chemical reactions in Ti/Si multilayered nanofilms
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塑性变形主导 Ti/Si 多层纳米膜的化学反应
DOI：
10.1016/j.msea.2018.09.031
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Minoshima Kohji
中科院分区：
文献类型：
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作者：
Hirakata Hiroyuki;Kawai Takashi;Kondo Toshiyuki;Minoshima Kohji
本研究的目的是阐明钛/硅多层纳米膜在机械载荷作用下的放热化学反应机理。利用扫描电镜对电子束蒸发法制备的多晶钛/非晶硅多层纳米膜（双层厚度~ 34 nm）进行了原位压缩实验。真应力随真应变的增加几乎呈线性增加，切模量在~ 3 GPa时开始减小。变形试样的透射电镜证实，各层在堆积方向发生塑性压缩，在面内方向发生膨胀，导致Ti/Si界面面积增大。选择区电子衍射分析表明，在Ti/Si界面和Ti层内产生了新的晶体结构ti5si4和/或TiSi。此外，试样的体积随着应变的增加而减小，这支持了发生化学反应的假设。在新的活性Ti/Si界面上，化学反应是由先前存在的复合层在平面方向上的拉伸应力导致的部分断裂引起的，或者是由扩散诱导的混合通过薄的复合层引起的。这些发现表明了通过局部机械负荷控制化学反应的可能性。所观察到的放热反应可用于各种应用，例如大规模微纳米器件的局部加热。
The purpose of the study was to clarify the exothermic chemical reaction mechanisms in Ti/Si multilayered nanofilms under mechanical loading. We conducted in situ compression experiments of truncated-cone specimens of polycrystalline-Ti/amorphous-Si multilayered nanofilms (bilayer thickness of ~ 34 nm) deposited by electron beam evaporation within a scanning electron microscope. The true stress increased almost linearly with increasing true strain and the tangent modulus began to decrease at ~ 3 GPa. Transmission electron microscopy of the deformed specimens confirmed that each layer was plastically compressed in the stacking direction and expanded in the in-plane direction, resulting in an increase in the Ti/Si interface area. Selected-area electron diffraction analysis revealed that a new crystal structure, proposed to be Ti5Si4and/or TiSi, was generated on the Ti/Si interface and within the Ti layer. In addition, the volume of the specimens decreased with increasing strain, supporting the hypothesis of a chemical reaction occurring. The chemical reaction was induced at the new reactive Ti/Si interface by the partial fracture of preexisting compound layers due to tensile stresses in the in-plane direction, and/or induced by diffusion-induced mixing through the thinned compound layers. These findings present the possibility of controlling the chemical reaction by local mechanical loading. The observed exothermic reaction can be used for various applications, such as local heating in large-scale micro- and nanodevices.