鈷原子團在 根號三乘根號三-銀/矽(111)面上聚集分布的研究 Condensation and distribution of Co cluster on root 3 by root 3-Ag/Si(111) surfaces

Abstract
本文是將鈷蒸鍍在 根號三乘根號三-銀/矽(111)面上,我們利用掃描穿隧顯微儀(STM)來研究鈷在銀所產生的根號三島上聚集與分布趨勢,在不同鍍量與不同溫度下,都出現了特別的現象。 我們分別改蒸鍍了0.9、1.35、1.8、2.25 ML的鈷,發現鈷有往邊緣堆積與鏈狀排列的趨勢,原因是根號三島上有某些區域的電子密度與空域密度特別高而造成鈷聚集。 接著改變不同的溫度,將蒸鍍1.8 ML的樣品加熱處理室溫~ 400 ℃,再降回室溫掃描。經加熱處理100 ℃後,鈷原子團邊緣堆積減少,而且整個根號三島上原子團也明顯變少,推測是鈷與銀相互交換造成。再加熱處理200 ~ 400℃,鈷原子團移動漸漸趨於平衡。 我們在升溫的過程中也發現了一些比較特殊的結構,例如根號三島上有一些突起的島,計算其高度,約是鈷一個單層的高度,研判是鈷鑽入所造成的隆起。我們也發現一些規則排列的三角結構,計算其原子間距,研判不是單純鈷、銀或矽的堆積,由於鈷銀不會有化學反應,也不是鈷銀化合物的堆積,推論應該是鈷矽化合物所產生的堆積。
The condensation and distribution of Co cluster on root 3 by root 3-Ag/Si(111) surfaces are studied in this thesis. Some special phenomena are observed by STM for depositing different Co coverage and annealing to different temperature. The four different coverage of Co on root 3 by root 3-Ag/Si(111) surfaces are 0.9ML、1.35ML、1.8ML and 2.25 ML. We find that Co clusters prefer to condense on the edges of root 3 islands and to arrange like a chain. The reason is that somewhere on root 3 islands has higher density of electron or vacancy state to attract Co cluster. Then we prepare 1.8ML Co/root 3 by root 3-Ag/Si(111) sample and anneal to five different temperatures, RT、100℃、200℃、300℃ and 400℃. After annealing to 100℃, Co clusters on the edges and on root 3 islands decrease. We infer that Co and Ag exchange after annealing to 100℃. We also find the movement of Co clusters tend to balance as temperature increasing. Other special features after annealing samples are found. For example, there are some bulges on root 3 island. After calculating the height of these bulges, we find the height is about 1ML Co, so infer that Co and Ag exchanged causes these islands rised. We also find some triangle arrangements which the distance between atoms is bigger than the lattice constants of Co、Ag and Si. And no composition exists between Co and Ag. So we infer these triangle arrangements are clusters of the Co-Si alloy.
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, , , 掃描穿隧顯微儀, Co, Si, Ag, STM, LEED
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