請用此 Handle URI 來引用此文件:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/48162
標題: | 奈米半導體、光子晶體、表面電漿子及磁性材料之新穎物理特性研究 Novel physical properties induced by nanostructured semiconductors, photonic crystals, surface plasmons, and magnetic materials |
作者: | Chih-Ming Wei 魏志銘 |
指導教授: | 陳永芳(Yang-Fang Chen) |
關鍵字: | 矽,鍺,矽鍺,氮化銦鎵,氮化鎵,量子井,自旋電流,光子晶體,表面電漿子,磁光效應,磁電效應, Si,Ge,SiGe,InGaN,GaN,quantum wells,spin current,photonic crystals,surface plasmons,magneto-optical,magnetoelectric, |
出版年 : | 2011 |
學位: | 博士 |
摘要: | 在本論文中,我們探討了由奈米半導體、光子晶體、表面電漿子及磁性材料等構成的複合物中所呈現的新穎物理特性。研究的結果可分為四個部分,分別是矽鍺/矽多重量子井中的自旋傳輸特性、利用光子晶體增強矽鍺/矽多重量子井的出光效率、利用磁場調制局域性表面電漿子共振頻率、以及將壓電半導體與磁性材料結合後所展現的磁電效應。
在第一部分中,我們研究了在矽鍺/矽多重量子井中的自旋傳輸特性。在價帶至導帶的躍遷激發條件下,圓偏振光致自旋電流與線偏振光致自旋電流皆同時被觀測到。藉由改變激發光的圓偏振程度,證實了在矽鍺/矽多重量子井中具有圓偏振光致自旋電流的特性。在此所觀測到的圓偏振光致自旋電流比在次級能帶間躍遷所產生的自旋電流約大十倍。圓偏振光致自旋電流與激發光入射角及入射強度的關係也與理論分析及預測相符。這些結果,對於自旋電子學在電子元件的發展及應用上有極大的助益。 在第二部分中,我們成功利用了三維光子晶體使矽鍺/矽多重量子井的出光效率提高。三維光子晶體中的光子禁帶在此可視為是反射鏡以及濾鏡。藉由此三維光子晶體的協助,我們可以選擇性地增強在矽鍺/矽多重量子井中的第二型躍遷所產生的光,並同時降低矽的發光。此一設計可延伸應用在其他的發光材料與系統中。此等結果非常適合用來發展高效率固態發光元件。 在第三部分中,我們成功地利用磁場以調控在貴重金屬奈米粒子及鐵磁性薄膜之複合物上之局域性表面電漿子的共振頻率。研究結果顯示,局域性表面電漿子的共振頻率及線寬可由外加磁場加以調整控制。造成此現象的原因,是由於鐵磁性薄膜在外加磁場下被磁化,該薄膜的介電常數因而產生改變,進而使得局域性表面電漿子的共振頻率及線寬同時改變。這個研究結果,證實了以磁場調控局域性表面電漿子的特性是可行的,同時在磁光及磁儲存裝置的發展上也有相當高的價值。 最後一部分,我們則是研究了壓電半導體與磁性材料所結合的複合物中之磁電效應。我們選用的壓電半導體為氮化銦鎵/氮化鎵多重量子井,而磁性材料則為鈷鐵合金。在外加磁場下,鐵磁薄膜會產生磁致伸縮,此一伸縮量會傳遞至壓電半導體,使壓電半導體產生壓電現象、改變其內部晶格結構狀態、電場分佈情形及能帶結構,進而在光學性質上有顯著的差異。此一研究結果顯示,壓電半導體與磁性材料結合後也能具有不錯的磁電性質,同時在磁光及磁電的元件開發上有一定程度的影響與幫助。 本論文的研究結果,不僅增進了吾人對由奈米半導體、光子晶體、表面電漿子及磁性材料等結合而成的複合物中所具有的物理特性的理解,同時對於相關自旋電子、光電、磁光以及磁電元件的開發與應用上有相當大的助益。 In this dissertation, we have reported the novel physical properties in the composites consisting of nanostructured semiconductors, photonic crystals (PCs), surface plasmons, and magnetic materials. The results can be divided into four parts which are spin transport in Si0.5Ge0.5/Si multiple quantum wells (MQWs), enhancement of luminescence extraction in Si0.5Ge0.5/Si MQWs by using PCs, manipulation of localized surface plasmon resonance (LSPR) by applying magnetic fields, and magnetoelectric (ME) effect in the composite consisting of piezoelectric semiconductors and ferromagnetic materials. In the first part, we have studied the properties of spin transport in Si0.5Ge0.5/Si MQWs. Circular photogalvanic effect (CPGE) and linear photogalvanic effect for interband transition have been observed simultaneously in Si0.5Ge0.5/Si MQWs. The signature of the CPGE is evidenced by the change of its sign upon reversing the radiation helicity. It is found that the observed CPGE photocurrent is an order of magnitude greater than that obtained for intersubband transition. The dependences of the CPGE on the angle of incidence and the excitation intensities can be well interpreted based on its characteristics. The large signal of spin generation observed here at room temperature should be very useful for the realization of practical application of spintronics. In the second part, we have successfully achieved the selective enhancement and suppression of the photoluminescence (PL) arising from Si0.5Ge0.5/Si MQWs by PCs. The formation of the stop band in PCs is designed to be a filter as well as a reflector. It is found that the self-assembled PCs are able to selectively enhance the luminescence of the type-II transitions at the interface between Si and Si0.5Ge0.5/Si layers and suppress the emission from Si. Our working principle shown here can be extended to many other material systems, and should be very useful for creating high power solid-state emitters. In the third part, magnetically tunable LSPR based on the composite consisting of noble metal nanoparticles and a ferromagnetic thin film have been demonstrated. It is found that both of the frequency and linewidth of the LSPR can be manipulated by applying an external magnetic field. The underlying mechanism is attributed to the variation of the dielectric constant in the ferromagnetic thin film resulted from the change of the magnetization. Our result shown here paves an alternative route to manipulate the characteristics of LSPR, which may be served as a new design concept for the development of magneto-optical devices. In the final part, The ME effect has been demonstrated based on the composite of the InGaN/GaN MQWs and the FeCo thin film. By applying an external magnetic field, the ferromagnetic layer will be deformed due to magnetostriction. This deformation is transmitted to the piezoelectric layers and results in piezoelectric effect, which induces electric polarization in the piezoelectric layers. The induced electric polarization changes the strain and the built-in internal electric field in the InGaN/GaN MQWs and therefore the optical properties of the InGaN/GaN MQWs change. The results shown here open up a possibility for the application of nitride semiconductors in magneto-optical and ME engineering. The novel phenomena discovered in this dissertation provides a more detailed understanding and potential applications of the composites consisting of semiconductor nanostructures, PCs, surface plasmons, and magnetic materials. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/48162 |
全文授權: | 有償授權 |
顯示於系所單位: | 物理學系 |
文件中的檔案:
檔案 | 大小 | 格式 | |
---|---|---|---|
ntu-100-1.pdf 目前未授權公開取用 | 3.27 MB | Adobe PDF |
系統中的文件,除了特別指名其著作權條款之外,均受到著作權保護,並且保留所有的權利。