Wang Dong, Zhang Zhenyu, Liu Dongdong, Deng Xingqiao, Shi Chunjing, Gu Yang, Liu Xiuqing, Liu Xiaoyu, Wen Wei
State Key Laboratory of High-performance Precision Manufacturing, Dalian University of Technology Dalian 116024 China
Beijing Spacecraft Manufacturing Co., Ltd., China Academy of Space Technology Beijing 100094 China.
Nanoscale Adv. 2024 Jan 3;6(8):2002-2012. doi: 10.1039/d3na00960b. eCollection 2024 Apr 16.
Copper (Cu) has a soft-plastic nature, which makes it susceptible to damages from scratching or abrasive machining, such as lapping and polishing. It is a challenge to control these damages as the damage mechanism is elusive. Nonetheless, controlling damages is essential, especially on the atomic surfaces of Cu. To interpret the damage mechanism, transmission electron microscopy (TEM) nanoindentation was performed using a cube-corner indenter with a radius of 57 nm at a loading speed of 5 nm s. Experimental results showed that damages originate from dislocations, evolve to stack faults, and then form broken crystallites. When the indentation depth was 45 nm at a load of 20 μN, damages comprised dislocations and stacking faults. After increasing the depth to 67 nm and load to 30 μN, the formation of broken crystallites initiated; and the critical depth was 67 nm. To validate the damage mechanism, fixed-abrasive lapping, mechanical polishing, and chemical mechanical polishing (CMP) were conducted. Firstly, a novel green CMP slurry containing silica, hydrogen peroxide, and aspartic acid was developed. After CMP, a surface roughness Ra of 0.2 nm was achieved with a scanning area of 50 μm × 50 μm; and the thickness of the damaged layer was 3.1 nm, which included a few micro-stacking faults. Lapping and mechanical polishing were carried out using a silicon carbide plate and cerium slurry, with surface roughness Ra values of 16.42 and 1.74 nm, respectively. The damaged layer of the former with a thickness of 300 nm comprised broken crystallites, dislocations, and stacking faults and that of the latter with a thickness of 33 nm involved several stacking faults. This verifies that the damage mechanism derived from TEM nanoindentation is in agreement with lapping and polishing. These outcomes propose new insights into understanding the origin of damages and controlling them, as well as obtaining atomic surfaces using a novel green CMP technique for soft-plastic metals.
铜（Cu）具有软塑性，这使其容易受到刮擦或研磨加工（如研磨和抛光）的损伤。由于损伤机制难以捉摸，控制这些损伤是一项挑战。尽管如此，控制损伤至关重要，尤其是在铜的原子表面上。为了解释损伤机制，使用半径为57 nm的立方角压头以5 nm/s的加载速度进行了透射电子显微镜（TEM）纳米压痕试验。实验结果表明，损伤起源于位错，发展为堆垛层错，然后形成破碎的微晶。当在20 μN的载荷下压痕深度为45 nm时，损伤包括位错和堆垛层错。将深度增加到67 nm且载荷增加到30 μN后，开始形成破碎的微晶；临界深度为67 nm。为了验证损伤机制，进行了固定磨料研磨、机械抛光和化学机械抛光（CMP）。首先，开发了一种新型的绿色CMP浆料，其包含二氧化硅、过氧化氢和天冬氨酸。CMP后，在50 μm×50 μm的扫描区域内实现了0.2 nm的表面粗糙度Ra；损伤层的厚度为3.1 nm，其中包括一些微堆垛层错。使用碳化硅板和铈浆料进行研磨和机械抛光，表面粗糙度Ra值分别为16.42和1.74 nm。前者的损伤层厚度为300 nm，包括破碎的微晶、位错和堆垛层错，后者的损伤层厚度为33 nm，涉及几个堆垛层错。这验证了由TEM纳米压痕得出的损伤机制与研磨和抛光一致。这些结果为理解损伤的起源和控制损伤，以及使用新型绿色CMP技术获得软塑性金属的原子表面提供了新的见解。
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