臺灣博碩士論文加值系統

中文摘要
本論文主要是在研究以分子束磊晶的方法成長γ-Al2O3在Si(111)基板上之晶體結構，性質與電性的關係，並與其他團體的結果做比較。研究的結果顯示，我們的實驗結果和別人比較起來有很明顯的改善。
在實驗方面，我在分子束磊晶系統裡以電子束蒸發高品質的藍寶石晶體來成長γ-Al2O3薄膜，並且以位於系統內的高能量電子繞射儀(RHEED)來辨別所成長之薄膜的品質，接著以X光來分析其晶體結構、與基板之間介面的平整度、與基板之間的方位關係，並且分析其電性。結果顯示，成長出來的氧化鋁薄膜為γ相並且其(111)軸和基板的(111)軸平行，且其厚度均勻，是一個理想的單晶薄膜。此結果可以用在將來繼續成長GaN/Al2O3 的參考。

Al2O3 films, electron beam evaporated from a high-purity single crystal sapphire source in UHV (a molecular beam epitaxy (MBE) approach), have been found to be epitaxially grown on Si (111) substrate. The structural studies were carried out by single crystal x-ray diffraction and transmission electron microscopy (TEM) with the initial epitaxial growth observed using in-situ reflection high energy electron diffraction (RHEED). The film morphology has also been studied by atomic force microscopy (AFM). The Al2O3 films grown in our MBE system have a cubic γ-phase with a very uniform thickness and a highly structural perfection, even for films as thin as 3.8 nm. The film thickness has been studied using low-angle x-ray diffraction (x-ray reflectivity) and cross-sectional TEM. The film normal was found to be <111>, which is well aligned with the Si substrate normal. All the in-plane unit cell vectors of the film are parallel to those of the substrate. A mosaic scan of the Al2O3 (222) peak (with no in-plane component) shows a 0.3 degree (or 18’) spread for a film 11 nm thick, while a 0.6 degree spread for a film 3.8 nm thick. A degenerate component (of ~ 10%) and 3o splitting were observed in x-ray phi-cone scans. A capping Si layer grown on top of the oxide film at a substrate temperature of 800 �aC is in a form of islands, not a smooth layer, as observed using x-ray reflectivity, TEM, and AFM. Nevertheless, the capping Si has the same orientation as that of the underlying Si (111) substrate. The interface between the γ-Al2O3 film and Si (111) was atomically sharp as observed using x-ray reflectivity and cross-section TEM. The electrical measurements show a low leakage current density of 10-7 A/cm2 and a breakdown field of 7 MV/cm for the oxide film 7.5 nm and a leakage current density of 10-1 A/cm2 and a breakdown field of ~10 MV/cm for the oxide film 3.8 nm thick.

TABLE OF CONTENT

I. Abstract ．．．．．．．．．．．．．．．．．．．．．．．．．．．．1
II. Introduction ．．．．．．．．．．．．．．．．．．．．．．．．．．．2
III. Instrumentation and Theory
Molecular beam epitaxy system ．．．．．．．．．．．．．．．．．．4
Single crystal X-ray diffraction．．．．．．．．．．．．．．．．．．．4
X-ray low angle reflectivity ．．．．．．．．．．．．．．．．．．．4
Spectral ellipsometry．．．．．．．．．．．．．．．．．．．．．．．6
Capacitance-voltage and current-voltage Characteristic007 ．．．．．．．7
Atomic force microscope．．．．．．．．．．．．．．．．．．．．．7
Transmission electronic microscope．．．．．．．．．．．．．．．．．8
IV. Experimental Procedure ．．．．．．．．．．．．．．．．．．．．．11
V. Results and Discussion
Structure of γ-Al2O3 ．．．．．．．．．．．．．．．．．．．．．．14
RHEED observation ．．．．．．．．．．．．．．．．．．．．．．14
Ellipsometry measurement．．．．．．．．．．．．．．．．．．．．15
X-ray measurement ．．．．．．．．．．．．．．．．．．．．．．15
AFM observation．．．．．．．．．．．．．．．．．．．．．．．．20
TEM observation ．．．．．．．．．．．．．．．．．．．．．．．21
I-V and C-V measurement ．．．．．．．．．．．．．．．．．．．．24
VI. Conclusion and Summary ．．．．．．．．．．．．．．．．．．．．．29
VII. Reference．．．．．．．．．．．．．．．．．．．．．．．．．．．．31

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