半導體奈米結構之研究與應用：氧化鋅、三族氮化物、以及其奈米複合材料

Studies and Applications of Semiconductor Nanostructures: ZnO, III-nitrides, and Their Nanocomposites

施函宇(Han-Yu Shih)

指導教授 ： 陳永芳

國立臺灣大學/理學院/物理研究所/博士(2012年)

https://doi.org/10.6342/NTU.2012.00133

摘要

本論文主要目的在於探討氧化鋅奈米結構、氮化銦鎵/氮化鎵多重量子井，以及其複合物之新奇物理特性，並發掘這些新奇特性的可能應用。我們所獲得的成果不論是在學術上或是工業上均有極大的應用潛力，今將主要成果摘要如下：
1. 藉由第二束低於能隙的光來調變氧化鋅一維奈米結構的光激螢光和光導電性
氧化鋅奈米柱和奈米絲帶的光激螢光和光導電性是可以藉由另一道低於能隙的光束來調變的。我們將第二道光束照射在氧化鋅奈米柱和奈米絲帶時，本來被第一道紫外線雷射激發的螢光和導電性都減弱了，而且我們藉由實驗來排除熱效應的可能性。當第二道光的波長為520 nm時，削弱效應最明顯，這個波長剛好對應到氧化鋅內兩個氧缺陷能階之間的躍遷。藉由不同直徑的奈米柱來重複以上實驗，我們驗證了缺陷存在於表面區域。藉由改變第二道光的強度來重複以上實驗，更支持了我們所提出來的機制。
2. 氮化銦鎵/氮化鎵多層量子碟受到外應力引發的對稱光學特性
我們研究了外力對氮化銦鎵/氮化鎵多層量子碟光學特性的影響。因壓電效應和量子侷限史塔克效應，當一股橫向應力施加在多層量子碟時，光激螢光和拉曼散射光譜都被改變了。有趣的是，光譜改變的行為呈現六角形對稱。這詭譎的現象可被歸因為晶格本身存在著六角形對稱，而且彈性薄膜又沿著某些特定的方向來拉扯樣品的晶格。此實驗成果可以提供另外一種面向來推廣與應用氮化物半導體所構成的光電元件並使其效能最佳化。
3. 氧化鋅奈米柱和氮化銦鎵/氮化鎵多層量子井構成可調變顏色的發光元件
我們將氧化鋅奈米柱成長在氮化銦鎵/氮化鎵多層量子上，我們建構了一種可發射兩種波長的新穎發光元件。有趣的是，這兩種發射光譜可以藉由偏振的選擇性來調變它們的相對強度。其背後的機制可歸因於這兩種奈米結構的幾何形狀恰好呈現互相垂直的方向。此實驗成果可以拓展到其他具有類似結構的複合材料，並且替可調變式發光元件開闢一個新的研究方向。
4. 藉由酵素修飾氧化鋅奈米柱和氮化銦鎵/氮化鎵多層量子井的光學特性來偵測葡萄糖
因奈米柱的表面積對體積比例很高，且氮化物壓電材料對電場很敏感，我們採用酵素修飾過的奈米柱與氮化物發光元件構成的複合材料來偵測葡萄糖分子。比起傳統必須監控電流的感測器，我們卻選擇監控發光元件的光譜，使測量和製程更加簡單。氧化鋅奈米柱和氮化銦鎵/氮化鎵多層量子井建構而成的感測元件暴露在葡萄糖溶液後，其光激螢光和拉曼散射光譜即產生顯著的變化。此實驗成果提供了一種新穎且高敏感度的光學式感測元件。
5. 藉由鉑粒子修飾氧化鋅奈米柱和氮化銦鎵/氮化鎵多層量子井的光學特性來偵測氫氣
延續前一個研究工作，我們採用包含鉑粒子修飾過的奈米柱與氮化物發光元件構成的複合材料來偵測氫氣分子。比起傳統必須監控電流的感測器，我們卻選擇監控發光元件的光譜，使測量和製程更加簡單。氧化鋅奈米柱和氮化銦鎵/氮化鎵多層量子井建構而成的感測元件暴露在葡萄糖溶液後，其光激螢光和拉曼散射光譜即產生顯著的變化。此元件的結構可推廣應用於感測其他種類的化學或生物分子。

關鍵字

半導體 ； 奈米科技 ； 氧化鋅 ； 三族氮化物

並列摘要

In this dissertation, we mainly focus on the study of the physical properties of ZnO nanostructures, InGaN/GaN multiple quantum wells, and their composites. Based on the discovered novel properties, we attempt to develop their potential applications. A brief description of our main findings has been summarized as follows. It is believed that our results shown here should be very useful for the general interests both in academics as well as industry
1. Tunable Photoluminescence and Photoconductivity in ZnO One-dimensional Nanostructures with a Second Below-gap Beam
Tunable photoluminescence (PL) and photoconductivity (PC) with a second below-gap beam were demonstrated on ZnO nanorods and nanoribbons. We found that both PL and PC could be quenched as the second beam was applied on the nanostructures, and this behavior was excluded from thermal effect by comparing the phonon replica spectra with that of heating the sample directly. The most quenching effect occurred near the defect transition locating at 520 nm. The underlying mechanism of the quenching behavior was attributed to the defect transition between different states of oxygen vacancies. Size-dependence measurement lets us know the effect occurs near the surface of nanostructures, and the power-dependent measurement further confirms the underlying mechanism we proposed.
2. Symmetrically Tunable Optical Properties of InGaN/GaN Multiple Quantum Disks by an External Stress
The influence of an external stress on the optical properties of InGaN/GaN multiple quantum disks (MQDs) has been investigated. As a transversal force is applied on the MQDs, both photoluminescence and Raman scattering spectra are altered due to the piezoelectric potential accompanied by the quantum confined Stark effect. Quite interestingly, it is found that the optical spectra possess a sixfold symmetry about the c-axis. This intriguing phenomenon can be attributed to the inherent nature of hexagonal lattice as well as the good flexibility of the composite consisting of polydimethylsiloxane and MQDs. Our results can provide an alternative route to optimize and extend the application of nitride-based devices.
3. Light-emitting Devices with Tunable Color from ZnO Nanorods Grown on InGaN/GaN Multiple Quantum Wells
Based on the composite consisting of ZnO nanorods (NRs) grown on InGaN/GaN multiple quantum wells (MQWs), we have demonstrated a novel light-emitting device (LED) that has the capability to emit dual beam radiations. Interestingly, the relative intensity between the dual emissions is able to be manipulated by their polarizations. The underlying mechanism can be well understood in terms of the anisotropic optical properties arising from the geometric structures of constituent nanoscale materials. The results shown here may be extended to many other nanocomposite systems and pave a new pathway to create LEDs with tunable properties.
4. Optical Detection of Glucose Based on the Composite Consisting of Enzymatic ZnO Nanorods and InGaN/GaN Multiple Quantum Wells
Based upon the high surface-to-volume ratio of nanorods and high sensitivity of piezoelectric properties of nitride semiconductors, enzymatic functionalized composite consisting of nanorods and nitride light emitting devices (LEDs) provide an excellent opportunity for the development of glucose detectors using optical methods. To demonstrate our working principle, a sensing device based on InGaN/GaN multiple quantum wells and ZnO nanorods has been constructed and exposed to target glucose solutions. The pronounced changes of emission as well as Raman scattering spectra under different target glucose concentrations clearly illustrate the feasibility of our newly designed composite for the creation of highly sensitive biosensors with optical detection.
5. Optical Detection of Hydrogen Gas Using Pt-catalyzed ZnO Nanorods and InGaN/GaN Multiple Quantum Wells
Based upon the high surface-to-volume ratio of nanorods and high sensitivity of piezoelectric properties of nitride semiconductors, catalyst decorated composite consisting of nanorods and nitride light-emitting devices (LEDs) provide an excellent opportunity for the development of gas detectors using optical methods. To demonstrate our working principle, a sensing device based on the composite consisting of InGaN/GaN multiple quantum wells (MQWs) and Pt-catalyzed ZnO nanorods has been fabricated and exposed to target hydrogen gas. The pronounced changes of emission as well as Raman scattering spectra of InGaN/GaN MQWs under different target gas concentrations clearly illustrate the feasibility of our newly designed composites for the creation of highly sensitive gas sensors with optical detection.

並列關鍵字

semiconductor ； nanotechnology ； ZnO ； III-nitrides

參考文獻

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