| Summary: | 碩士 === 國立臺灣師範大學 === 物理研究所 === 92 === 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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