本文主要探討以電漿輔助化學氣相沉積法(Plasma Enhanced Chemical Vapor Deposition, PECVD)製備核殼結構(Core-Shell structure)之氮化鎵(Gallium Nitride, 氮化鎵)奈米線的成長行為。製備Core-Shell 氮化鎵奈米線主要可分為兩個步驟，分別為氮化鎵奈米線的製備以及氮化鎵 Shell的製備兩個步驟。在製備氮化鎵奈米線的時候，其成長機制主要是固液氣相成長機制(Vapor-Liquid-Solid Mechanism, VLS Mechanism)，這是一種以金做為觸媒吸附氣相中的鎵蒸氣，在特定溫度下行成金鎵合金。當其吸收過量的鎵時，無法被液態合金相的金所吸收的鎵就會於金觸媒與基板的介面上析出鎵，並與氣相中具高反應性的氮活性基產生反應，生成固相的氮化鎵。氮化鎵Shell的成長機制是一種固氣相成長機制(Vapor-Solid Mechanism, VS Mechanism)，當氣相中的鎵原子以單層吸附的方式吸附於氮化鎵奈米線的表面且於表面的Ga / N比達一定程度，氮化鎵就會以VS成長機制成長於氮化鎵奈米線的表面上，而這些成長出來的氮化鎵即為氮化鎵Shell。
在氮化鎵奈米線成長的部份，本研究成功製備出單晶wurtzite結構的氮化鎵奈米線，其成長方向與鎵的蒸氣壓多寡無關，皆為<1 -1 0 0>。在製備氮化鎵奈米線時，鎵蒸氣壓越大，所製備出的奈米線的長度以及直徑的均勻性越差。此外，成長時間越長，奈米線的長度以及直徑的分佈會變廣且奈米線頂端會有出現尖錐狀的現象。此外由PL頻譜分析可以得知，當鎵蒸氣壓越高，c-plane Ga face的相對量越多。成長時間越長，IDB的相對量也越多。由PL及SEM檢測結果發現金屬鎵溫度850℃成長時間30分鐘的製程所製備的氮化鎵奈米線品質良好，其長度以及直徑分佈最均勻，奈米線平均直徑也最細。
在氮化鎵Shell成長的部份，發現當奈米線頂端的金觸媒不移除時，所製備的氮化鎵Shell 形貌、長度分佈以及直徑分佈差異會極大。移除奈米線頂端的金觸媒所製備的氮化鎵Shell 形貌、長度分佈以及直徑分佈都比未移除金觸媒所製備的氮化鎵Shell均勻，此外當基板溫度越高，氮化鎵 Shell的長度以及直徑尺寸的分佈較均勻。
此外本研究成功開發出一種一步製備Core-Shell structure 氮化鎵 nanowire的製程，此製程具備省時、低碳污染以及節省能源等優點。由PL分析結果顯示一但氮化鎵奈米線在製作氮化鎵 Shell的製程前暴露在大氣下，其必然會有碳汙染的問題。當Core-Shell structure氮化鎵奈米線以此製程製備，其PL頻譜就不會有YL，顯示此製程所製備的氮化鎵 Shell內部並未存在碳參雜，對磊晶的品質有極大的助益。

This thesis mainly focuses on developing a novel process to fabricate high quality Core-Shell structure of GaN nanorod via PECVD and studying parameter relationships between sizes, shapes, morphologies, atomic ratios, and defects in different processes. The Core-Shell structure of GaN nanorod is fabricated in two distinct method—Growth of GaN nanowires via VLS mechanism and growth of GaN Shell via VS mechanism. In fabrication of 1-D nanostructures by CVD process, VLS mechanism is commonly found. We used gold as the catalyst to enhance the VLS mechanism for making GaN nanowires in this research. Another growth mechanism, VS mechanism, is mostly applied to thin film CVD processes. To promote VS mechanism, high Ga vapor pressure was applied to create a surrounding which increases the tendency of VS mechanism for GaN Shell growth during this process. Growth time and Ga vapor pressures were set as the experimental parameters in this study to observe variation in GaN nanowires, while substrate temperatures and Au existence are the experimental parameters in GaN Shell process.
For GaN nanowires’ results, single crystal GaN nanowires in wurtzite structure were successfully made with the growth orientation in <10-10> independent to the Ga concentration in gas phase. GaN nanowires’s aspect ratos (L/D), lengths, diameters, and distributions are affected by the Ga concentration in gas phase. When the process is under high Ga concentration in gas phase , we found that the as-grown nanowires became shorter, thinner, and widely distributed in length and diameter with the aspect ratios less than the ones under lower Ga. The effect of growth time is similar to that of Ga concentration in gas phase—the longer the growth time, the heavier the nanowires. The PL measurements showed that the quality of GaN nanowires are much more superior than the common GaN thin film made by MOCVD.
For GaN Shells results, we have successfully developed two kind of novel processes—Removing gold in low pressure process, and single process to make Core-Shell structure GaN nanorod without evacuated to atmosphere during the process. Results showed that the GaN nanowires are much thicker than before with crystal-like shapes found. The GaN on the substrate demonstartes two different morphologies when the gold remains on substrate—the grass-shaped nanobelts and the crystal-shaped nanorods. The gold remained on the substrate may be activated to form the 2nd order VLS mechanism which lead to grass-shaped nanobelts. However, such phenomena was not observed from the other GaN Shell process.

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