Real time dynamics of Si magic clusters mediating phase transformation: Si(111)-(1 ¡Á 1) to (7 ¡Á 7) reconstruction revisited

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• 作者：Wei Jie Ong ; Eng Soon Tok ; ^{phytokes@nus.edu.sg}
• 关键词：Scanning tunneling microscope ; Surface reconstruction ; Magic clusters ; Phase transformation
• 刊名：Surface Science
• 出版年：2012
• 出版时间：July, 2012
• 年：2012
• 卷：606
• 期：13-14
• 页码：1037-1044
• 全文大小：2609 K

文摘

Using Scanning Tunneling Microscope (STM), we show that the surface undergoes phase transformation from disordered ? ¡Á 1?to (7 ¡Á 7) reconstruction which is mediated by the formation of Si magic clusters. Mono-disperse Si magic clusters of size ~ 13.5 ¡À 0.5 ? can be formed by heating the Si(111) surface to 1200 ¡ãC and quenching it to room temperature at cooling rates of at least 100 ¡ãC/min. The structure consists of 3 tetra-clusters of size ~ 4.5 ? similar to the Si magic clusters that were formed from Si adatoms deposited by Si solid source on Si(111)-(7 ¡Á 7) [1]. Using real time STM scanning to probe the surface at ~ 400 ¡ãC, we show that Si magic clusters pop up from the (1 ¡Á 1) surface and form spontaneously during the phase transformation. This is attributed to the difference in atomic density between ¡°disordered 1 ¡Á 1?and (7 ¡Á 7) surface structures which lead to the release of excess Si atoms onto the surface as magic clusters.