Au Nanoparticle Formation from Amorphous Au/Si Multilayer

• 作者: Hiroshi Abe Katsuhiko Inaba Masami Aono Shintaro Kobayashi Takashi Ueda
• 来源期刊: 结晶过程及技术期刊(英文)
• 学科: 化学
• 关键词: AMORPHOUS Au/Si MULTILAYER AU NANOPARTICLE Low EUTECTIC Point Metal Induced Crystallization IRREVERSIBLE Morphological Transformation Reversible l-AuSi-c-Au NANOPARTICLE Phase Transition
• 年，卷（期）: 2014,（4）
• 页码范围: 193-205
• 页数: 13页
• 分类号: O6

摘要

By direct observations of transmission electron microscopy (TEM), irreversible morphological transformations of as-deposited amorphous Au/Si multilayer (a-Au/a-Si) were observed on heating. The well arrayed sequence of the multilayer changed to zigzag layered structure at 478 K (=Tzig). Finally, the zigzag structure transformed to Au nanoparticles at 508 K. The distribution of the Au nanoparticles was random within the thin film. In situ X-ray diffraction during heating can clarify partial crystallization Si (c-Si) in the multilayer at 450 K (= ), which corresponds to metal induced crystallization (MIC) from amorphous Si (a-Si) accompanying by Au diffusion. On further heating, a-Au started to crystallize at around 480 K (=Tc) and gradually grew up to 3.2 nm in radius, although the volume of c-Si was almost constant. Continuous heating caused crystal Au (c-Au) melting into liquid AuSi (l-AuSi) at 600 K (= ), which was lower than bulk eutectic temperature ( ). Due to the AuSi eutectic effect, reversible phase transition between liquid and solid occurred once temperature is larger than . Proportionally to the maximum temperatures at each cycles (673, 873 and 1073 K), both and Au crystallization temperature approaches to . Using a thermodynamic theory of the nanoparticle formation in the eutectic system, the relationship between and the nanoparticle size is explained.