Microstructure and growth mechanism of tin whiskers on RESn₃ compounds

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• 作者：Cai-Fu Li ; Zhi-Quan Liu ; ^{zqliu@imr.ac.cn}
• 关键词：Intact tin whisker ; RESn3 compounds ; In situ ; Transmission electron microscopy (TEM)
• 刊名：Acta Materialia
• 出版年：2013
• 出版时间：January, 2013
• 年：2013
• 卷：61
• 期：2
• 页码：589-601
• 全文大小：1663 K

文摘

An exclusive method was developed to prepare intact tin whiskers as transmission electron microscope specimens, and with this technique in situ observation of tin whisker growth from RESn₃ (RE = Nd, La, Ce) film specimen was first achieved. Electron irradiation was discovered to have an effect on the growth of a tin whisker through its root. Large quantities of tin whiskers with diameters from 20 nm to 10 ¦Ìm and lengths ranging from 50 nm to 500 ¦Ìm were formed at a growth rate of 0.1-1.8 nm s^?1 on the surface of RESn₃ compounds. Most (>85 % ) of these tin whiskers have preferred growth directions of ¡´1 0 0¡µ, ¡´0 0 1¡µ, ¡´1 0 1¡µ and ¡´1 0 3¡µ, as determined by statistics. This kind of tin whisker is single-crystal ¦Â-Sn even if it has growth striations, steps and kinks, and no dislocations or twin or grain boundaries were observed within the whisker body. RESn₃ compounds undergo selective oxidation during whisker growth, and the oxidation provides continuous tin atoms for tin whisker growth until they are exhausted. The driving force for whisker growth is the compressive stress resulting from the restriction of the massive volume expansion (38-43 % ) during the oxidation by the surface RE(OH)₃ layer. Tin atoms diffuse and flow to feed the continuous growth of tin whiskers under a compressive stress gradient formed from the extrusion of tin atoms/clusters at weak points on the surface RE(OH)₃ layers. A growth model was proposed to discuss the characteristics and growth mechanism of tin whiskers from RESn₃ compounds.