氧化鎂在Si(111)及石墨上成長形態之研究

The Growth Morphology of MgO on Si(111) and Graphite

梁志繹(Jhih-Yi Liang)

指導教授 ： 門福國

國立中正大學/理學院/物理學系/碩士(2013年)

摘要

在半導體上成長MgO薄膜，之後於薄膜上再成長鐵磁/非磁性金屬多層膜，發現鐵磁金屬膜上產生垂直磁異向性，而MgO薄膜扮演著重要的角色。實驗中我們備置了Si(111)與高方向性熱解石墨兩種基板，並於這兩種基板上成長MgO薄膜，藉由穿隧式電子顯微鏡和原子力顯微鏡，分別在真空及大氣下觀察表面MgO團簇生長情形。

觀察結果發現在Si(111)-(7×7)重構面上成長MgO薄膜，其團簇會由最初的隨機分布，經基板溫度升高，逐漸形成團狀分布及沿台階方向生長的長條狀團簇。而成長於高方向性熱解石墨上的MgO薄膜，可發現大部分團簇喜好沿著階梯邊緣生長，且團簇的密度分布極為不均，經由背板加熱可使其團簇增大，間接呈現了Ostwald ripening機制，並將磊晶好的樣品置於大氣24小時之後，觀察到分布密度均勻的MgO團簇，且於48小時後發現多角狀晶體的產生，比較MgO成長於此兩種基板上，我們皆可觀察到團狀分布及長條狀原子團簇的兩種成長形態。

關鍵字

磊晶 ； 石墨 ； 矽 ； 氧化鎂 ； 成長形態

並列摘要

By growing MgO thin film on a semiconductor substrate and then growing ferromagnetic/non-magnetic metal multilayers on the MgO film, literature has reported that the ferromagnetic metal film shows perpendicular magnetic anisotropy, indicating the MgO film plays a crucial role in the perpendicular anisotropy. In our experiment, Si(111) and highly oriented pyrolytic graphite (HOPG) substrates have been used to grow MgO film. Scanning tunneling microscopy and atomic force microscopy, respectively in vacuum and under atmospheric pressure, were employed to observe surface morphology.

Our observations show that, by growing MgO on a Si(111)-(7×7) surface, randomly distributed MgO clusters coalesce to form elongated chain structure in a direction parallel to the surface step after heating the MgO-deposited surface. For MgO growing on a HOPG surface at room temperature, we have found that the MgO clusters distribute rather unevenly on the surface. Most MgO clusters tend to grow along the step edges, leaving terraces virtually free of clusters. The MgO clusters coalesce and large clusters emerge after heating, an indication of Ostwald ripening at work. We have intentionally placed a MgO-grown HOPG surface in the atmosphere for extended period of time. After 24 hours, uniformly distributed MgO clusters show up on the surface. Regularly shaped clusters, i.e., crystalline MgO clusters, emerge after 48 hours of exposing in the atmosphere. Though growing on two drastically different substrates, the kinetics of MgO growth appears to show a similar pattern: clustering followed by coalescence into elongated chain structure.

並列關鍵字

Deposition ； Growth ； Epitaxy ； Graphite ； Si(111) ； MgO

參考文獻

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