用掃描式穿隧顯微鏡研究順式二苯乙烯吸附在鍺(100)表面

Abstract

有機分子在半導體表面上所形成自組裝和吸附行為，近年來被研究的 非常廣泛。本篇論文主要是利用掃描式穿隧顯微鏡(Scanning Tunneling Microscopy，STM)，來觀測Ge(100)表面在室溫和低溫下所呈現的結構不 同，以及研究二苯乙烯(Stilbene)在Ge(100)表面上的吸附位置，和吸附與 脫附的現象。 室溫下用STM偵測Ge(100)表面，偵測出STM影像大部份呈現(2×1)的 結構，而低溫下幾乎是呈現c(4×2)的結構。因為Ge(100)表面上鍺原子以 二聚體的形式存在，鍺二聚體在室溫下快速進行flip-flop運動，在STM影 像中鍺二聚體為一亮點，呈現(2×1)的結構；鍺二聚體在低溫下flip-flop運 動較緩慢，鍺二聚體中高的原子(up-atom)形成一亮點，會出現c(4×2)和 p(2×2)的結構，大部份是c(4x2)的結構。 有機分子二苯乙烯吸附在Ge(100)的表面上，大部份的Stilbene會以相 同的方向排列，只有少數的分子會以不同的方向吸附。二苯乙烯化學吸 附在Ge(100)表面，二苯乙烯的乙烯雙鍵會和鍺二聚體發生成環反應。在 多層吸附下，二苯乙烯分子彼此間為物理吸附，會因加熱二苯乙烯脫附 ，加熱至不同溫度產生不同的覆蓋度(coverage)。Recently, the adsorption and self-ordered organic molecules on semiconductor surfaces have been investigated extensively. We investigated the adsorption and desorption of Stilbene on a Ge(100) surface using scanning tunneling microscopy (STM). The STM images show Ge(100) surface structure are different at room temperature and low temperature, and the arrangement of Stilbene on Ge(100) is directive. Ge dimer flip-flop and result in the (2×1), c(4×2) and p(2×2) structures. The STM images of Ge(100) surfaces were obtained and showed an ordered (2×1) domain pattern at room temperature(~298 K). At low temperature (liquid nitragen ~90 K) the surface were obtained that showed ordered c(4×2) domain pattern and a part of p(2×2) structure. Stilbene molecules absorb on the Ge(100) surfaces mainly through the cycloaddation reaction between the vinyl group of Stilbene and the Ge dimer. Most of Stilbene molecules adsorbed and arranged on Ge(100) surface in the same direction, but some Stilbene adsorbed in different configuration.