In-Situ Strengthening Method for Micro-Sized materials for MEMS devices by Nanocrystal Precipitation During Application of Stress

微机电系统（MEMS）在信息技术、生物医学技术等诸多科技领域得到了广泛的发展和应用。这些MEMS器件通常是通过合适的表面微加工技术将薄膜沉积在衬底上制成的，并且从薄膜层制备的微尺寸元件用作机械元件。因此，在这种装置中使用的部件的尺寸被认为是在微米的数量级，并且这种微尺寸材料的机械性能被认为与散装（普通尺寸）材料不同。因此，开发用于MEMS应用的高性能材料是必要的。由于MEMS器件的尺寸都在微米量级，仅通过微细尺寸的结构修改来控制材料的力学性能已经不够，因此采用常规的强化方法对微细尺寸材料进行强化是相当困难的。因此，基于纳米结构控制的强化将是微尺寸材料最有前途的强化方法之一，需要开发纳米结构控制的强化方法。本文研究了Ni-P非晶合金薄膜在应力场作用下纳米晶的析出。采用聚焦离子束加工方法制备了微尺度悬臂梁型试样，并利用微尺度试件力学试验机对试样施加弯曲应力。在平面应变变形区透射电镜观察发现，变形诱导析出纳米晶Ni颗粒，且所有晶体颗粒的（III）平面平行于试样侧面。纳米晶的析出被认为是微尺寸非晶合金原位强化的有效方法。

Microelectromechanical systems (MEMS) are under intensive development for utilization in many scientific and technological fields such as information and biomedical technologies. These MEMS devices are usually fabricated from a thin film deposited on a substrate by suitable surface micromachining techniques, and the micro-sized elements prepared from a thin film layer are used as mechanical components. The size of the components used in such devices is thus considered to be in the order of microns, and the mechanical properties of such micro-sized materials are considered to be different from those of bulk (ordinary sized) materials. The development of high performance materials for MEMS applications is thus necessary. It is rather difficult to apply conventional strengthening methods for micro-sized materials, as the size of MEMS devices are of the order of microns and controlling the mechanical properties based on micro-size structural modifications is no longer adequate. Therefore, strengthening based on nanostructural control would be one of the most promising methods for micro-sized materials and the development of strengthening methods by nanostructural control are required. In this investigation, precipitation of nanocrystals in a Ni-P amorphous alloy film during application of a stress field was investigated. Microsized cantilever-beam-type specimens were prepared from the film by focused-ion-beam machining and bending stress was applied to the specimen using a mechanical testing machine for microsized specimens. Transmission electron microscopy observation in the plane strain deformed region has revealed that the deformation induces the precipitation of nanocrystalline Ni particles, and a (III) plane of all crystalline particles is aligned parallel to the side surface of the specimen. The precipitation of nanocrystals is considered to be effective for in-situ strengthening of micro-sized amorphous alloy.