光電子能譜及低能量電子繞射儀研究鉛薄膜在鍺(111)基底上之電子結構與薄膜性質

Studies of the electronic structures and thin film properties of Pb on Ge(111) by Photoemission and LEED

黃建中(Chien-Chung Huang)

指導教授 ： 唐述中

國立清華大學/理學院/物理學系/碩士(2009年)

https://doi.org/10.6843/NTHU.2009.00458

摘要

我們成功的在n型高摻雜的鍺(111)基底上製備原子平坦的鉛薄膜並利用高解析度的角解析光電子能譜研究鉛薄膜在鍺(111)基板上的電子結構，測量了2至20層的鉛薄膜(在β-phase √3×√3R30° 重構結構上)的量子井電子態。位在鍺(111)基底 位置的量子井電子態可以成功的以Bohr-Sommerfeld量子化規則來計算出其量子井電子態初始能量和薄膜厚的關聯，我們發現量子井電子態的理論值與實驗值相當的吻合。另外，我們也對2至15層的鉛薄膜進行的薄膜熱穩定的量測，從中我們觀察到鉛薄膜熱穩定溫度會隨薄膜的層數有高低震盪的現象(Bilayer Oscillation)；並且還觀察到每經過9層的週期，鉛薄膜熱穩定會有反轉的現象(Beating Effect)，即原本偶(奇)數層為穩定層時會反轉成奇(偶)數層為穩定層。最後我們利用低能量電子繞射儀來觀測鉛薄膜在鍺(111)基底上的原子排列情況，其中我們觀察到鉛薄膜從2層到4層時薄膜的成長有很明顯的改變；2層的鉛薄膜成長是沿著平行鍺(1×1)基底方向，從3層後鉛薄膜是沿著鍺(1×1)旋轉30°的方向成長。從2層鉛薄膜的成長中我們可以得知，鉛薄膜與 n型高摻雜的鍺基底間其電子與電子間強烈的相互作用影響了薄膜的成長。

關鍵字

量子井態 ； 鉛 ； 薄膜

並列摘要

Atomically uniform Pb films on Ge(111) were successfully pre-pared at　the thickness ranging 2-20 monolayer above dense β-phase √3×√3R30° reconstruction and measured by Angle Resolved Photoemission. The measurement of the thickness dependence of the electronic structures for Pb films on Ge(111) was performed and the peak positions of QWS were analyzed by Bohr-Sommerfeld quantization rule. The measured peak positions match the theoretically predicted values very well. The thermal stability of Pb film was studied by annealing the Pb films and measuring the thermal stability temperature. The stability temperatures exhibited a thickness-dependent oscillation with a bilayer period and beating of 9 ML. We studied lattice structure by Low Energy Electron Diffraction. Initially at 2 ML, Pb films grow in the same direction as the Ge(111) substrate. Then above 2 ML, part of Pb films grow in a new direction which was rotated 30° with respect to Ge(111) substrate. With increasing thickness, these two domains of 2D Pb islands coexist and compete with each other. The electron-electron interaction between the film and highly doped n-type Ge(111) substrate influence the formation of islands.

並列關鍵字

quantum well state ； Pb ； film

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