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Title: | 矽基材料之表面及光學特性研究 Surface and Optical Properties of Silicon-based Materials |
Authors: | Li-Chi Cheng 鄭立琦 |
Advisor: | 馮哲川 |
Keyword: | 氧化矽,碳化矽,光致螢光光譜,傅氏光譜,拉曼光譜, silicon oxides,silicon carbides,photoluminescence,Fourier transform infrared spectroscopy,Raman spectroscopy, |
Publication Year : | 2007 |
Degree: | 碩士 |
Abstract: | 在本論文中,我們研究了兩種不同的材料,以達到在矽基材料上將光放大及發光之目的。
第一種是在在矽(111)基板上成長氧化矽,並將鑭系元素-鋱,以離子佈植的方式植入樣品。在常溫和低溫的光致螢光光譜中,我們可以觀察到鋱的三價離子,於4f能帶內局部的躍遷而放出的光。X光繞的結果顯示,以電漿輔助化學氣相沉積成長之樣品,SiO2(211)和SiO2(301)這兩個晶面會消失,但卻不會影響光致螢光光譜,相反地,Tb2O3(600)的晶面若經退火後消失,光致螢光的現象就會較不明顯。傅氏光譜量測的結果顯示在約1090 cm-1的地方有很強的吸收,這表示在Si-O-Si的鍵結中,氧原子以不對稱振動的方式,平行於Si-Si鍵結的方向振動,這個結果與拉曼光譜量測的結果顯示,本次實驗之氧化矽樣品含有很多有序的Si-O-Si鍵結,有極高之化學鍵結的穩性。X光-光電子能譜的結果則顯示,在爐管中熱退火,會使樣品表面氧的含量提高並造成氧原子的空缺,這些額外氧原子的空缺來自於表面下方的Si-O-懸鍵 (被熱退火破壞的氧化矽),並向表面聚集;氧原子的空缺則扮演了輻射的復合中心角色,使得光致螢光的現象更為明顯;另一方面,由於鋱離子的高濃度(彼此的距離更小),經退火後,造成綠光的增強(以藍光衰減作為代價),這是因為能量的交互弛豫(在5D3-5D4與7F0-7F6間)。 另一種則是在矽(100)基板上,以化學氣相沉積成長之立方晶系之碳化矽。拉曼光譜顯示了,在約974 cm-1有明顯的峰值,這代表著碳化矽LO聲子的訊號,隨著成長時間(厚度)的增加而增加(相較於來自矽基板的訊號);另一方面,X光光電子能譜則揭露了碳化矽的表面含有厚度約2 nm之碳氫化合物,這是來自於未反應的反應氣體SiH4C3H8。 Because of great motivation to develop the light amplifiers and emitters from Si or Si-based materials, we have promoted two different kinds of light-emitting mechanisms to achieve the goal. One of them is to implant terbium ion into silicon oxides thin film which is grown on Si(111) substrates. Trivalent terbium (the preferred bonding state) has an incomplete 4f electronic shell (54[Xe]4f95d06s2) that is shielded from the outer world by inner 5s and 5p shells. As a result, the intra-4f transitions can be achieved from terbium doped materials. The structure of samples are studied by X-ray diffraction (XRD), and then show that the lattice planes of SiO2(211) and SiO2(301) disappeared if the plasma treated processes are added. The disappearance of SiO2(211) and SiO2(301) would not influence the results of photoluminescence (PL). In contrast, the PL intensity decreases since Tb2O3(600) disappears after annealing. The results of Fourier transform infrared (FT-IR) spectroscopy reveal that there are obvious dropping peaks at 1090 cm-1 which denote the asymmetric stretching vibration mode of Si-O bonding. The vibrational direction of Si-O bonding is parallel to the Si-Si bonding. The results of FT-IR and Raman spectroscopy lead us to the conclusion that the films are rich in Si-O-Si bonds and have an orderly silica network. Consequently, they are in good chemical stability. The result of X-ray photoelectron spectroscopy (XPS) exhibits the excess oxidation at the surface for the samples annealed in the furnace. The surface excess oxygen atoms come from the dangling Si-O- bonding which are damaged in the place under the surface, and incline to assembling towards the surface. The oxygen vacancies also play a role of radiative recombination center which enhance the recombination rate between electrons and holes. On the other hand, the phenomenon of “cross-relaxation” (between 5D3-5D4 and 7F0-7F6) arises since high Tb concentrations. It causes the increase of green lines at the expense of blue lines. Another is chemical vapor deposition (CVD)-grown 3C-SiC on Si(100) substrates. The results of Raman spectroscopy indicate that the intensity from 3C-SiC LO phonon increases gradually compared with that from Si substrates with the thickness of 3C-SiC increasing. Besides, it can be seen that forbidden TO modes decrease in intensity with respect to the allowed LO modes with increasing growth times. The XPS results showed that the surfaces of the samples consist of Si oxides and unreacted CH (2nm), in addition to the stoichiometric SiC compound. The elemental Si which is attributed to unreacted Si atoms is absent in this work. The CH species on the surface of the 3C-SiC films are a result of unreacted SiH4 and C3H8 or their reaction intermediates. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/24961 |
Fulltext Rights: | 未授權 |
Appears in Collections: | 光電工程學研究所 |
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