鉑的重構-皺化與失蹤原子列的觀察與研究

Abstract

本研究中，我們利用場離子顯微鏡觀察鉑的皺化與失蹤原子列的表面重構。表面的皺化與失蹤原子列的產生，都是為了得到最低的表面自由能而去改變表面的形貌。因此本文就以這兩個方向加以深入討論。皺化方面，當加熱退火的溫度逐漸提升，包括了(111)、(100)、(311)、(110)等表面自由能較低的指數面會漸漸擴張，此外在加熱至700K以上，(310)面也發生了擴張的行為，是本實驗中最令人振奮的發現，這也說明了就算擁有較低表面自由能的指數面，若給予的能量未達該指數面原子該有的動態能量，依然不會有皺化行為的發生。失蹤原子列方面，失蹤原子列的表面形貌在(110)面及(311)面是(1×1)變成(1×2)的結構，而在(331)面及(211)面而言都是(1×1)變成表面兩層(1×2)的結構，這種結構可以是原子的增加、消失，亦或是原子跳動，在此我們將這種行為與皺化的表現做結合，發現兩者是相輔相成、同時存在的，並且發現在表面重構發生後，各指數面交界仍然保持連續。另外(311)面則在加熱到650K之後，會再由(1×2)的結構，再次轉為(2×2)的重構。另外本實驗對合金Pt80Ir20以場離子顯微鏡做形貌上的觀察，發現合金擁有較強的鍵結，並且在(100)面已經可以看到超晶格的結構。 Faceting and missing-row of Pt surface reconstruction are observed by field ion microscopy (FIM). In order to reducing the surface energy, it may facet and forms the missing-row on the surface. In the point of view for faceting, while anneal temperature increases, those low-surface-free-energy surfaces including (111)、(100)、(110)、(311) extend. As the temperature is arising to 700K, the (310) surface starts to extend. This implies that even though the surface free energy is low enough, the surface still cannot facet if the applied energy is lower than the dynamic energy of surface atoms. In the point of view for missing-row, surface structures reconstruct from (1×1) to missing-row (1×2) on (110), (311), (331) and (211) surfaces. (331) and (211) surfaces have two mono-layer (1×2) reconstructions. This structure can be attributed to adding-atom, missing-atom, or atom-jumping. This behavior corresponds to faceting simultaneously. The surface borders of different index keep connected after surface reconstruction. Besides, (113) surface reconstructs again from (1×2) to (2×2) at 650K. In addition, Pt80Ir20 alloy are also observed in this study. The observation shows that the bond in this alloy is strong, and there are superlattice structures on (100) facets.