改善種子層並利用水熱法生長可控制尺寸與導向之氧化鋅微奈米柱陣列之研究

Improving the seed layer and controlling the size and growth orientation of ZnO micro/nanorod arrays by hydrothermal method

林文瀚(Wen-Han Lin)

指導教授 ： 林清富

國立臺灣大學/電機資訊學院/電機工程學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.02207

摘要

本論文的研究主要在於探討如何利用水熱法製作具有良好導向、高品質的氧化鋅微奈米柱。在論文之中，我們首先介紹了如何以溶膠-凝膠方法製備氧化鋅薄膜以及以水熱法製備氧化鋅微奈米柱。接著我們探討了退火對於氧化鋅薄膜與成長氧化鋅微奈米柱的各種影響，然後利用了在退火之前鍍金的製程製作出平整的氧化鋅種子層，成功的改善了氧化鋅微奈米柱的尺寸與導向，並在最後討論了如何改變現有的LED結構的構想，並且以氮化鎵基板為種子層成長氧化鋅微奈米柱達到限制生長位置的目的。

我們以掃描式電子顯微鏡分析氧化鋅薄膜表面的型態對於退火製程所產生的變化，並且在不同退火溫度的氧化鋅薄膜使用不同濃度的生長溶液成長氧化鋅奈米柱，探討退火製程與奈米柱尺寸之間的關係。氧化鋅薄膜在900度的溫度退火時能得到較大的結晶顆粒，能夠成長尺寸較大的氧化鋅奈米柱，但是因為大顆粒造成的表面粗糙會造成奈米柱的導向不佳，若是將氧化鋅薄膜在退火之前預先鍍上一層金後再次退火，便能得到一個平整的表面。我們將經過鍍金製程的氧化鋅奈米柱與未經過鍍金製程的氧化鋅奈米柱進行XRD分析，比較此兩種奈米柱的結晶特性，發現前者得到了較高品質的氧化鋅奈米柱，之後進行光激發光的量測，發現經過鍍金製程成長的氧化鋅奈米柱中的氧空缺變少，晶格結構更加完整。而從能量散佈光儀圖中看出去除黃金的薄膜上只有鋅、氧、矽元素存在，種子層上並沒有黃金的殘留，可以確定氧化鋅奈米柱並不是從金奈米粒子上成長出來的。

我們根據以上等資訊、氧化鋅薄膜表面的型態加上相關的參考文獻，對於鍍金製程改善氧化鋅奈米柱的導向與尺寸的原因進行了推論。當鍍上金之後形成一個保護層，這層金屬薄膜的覆蓋在種子層上的作用就好像是做了壓制一般的效果，限制了氧化鋅溶膠凝膠薄膜在做退火製程之後的結晶方向，使得退火時薄膜的結晶能夠朝著x-y平面來發展，而減少氧化鋅形成結晶聚集時往z軸的方向前進。此製程有效的改善了在高溫退火之下導致的種子層不平整，成功的製作出大尺寸且有良好導向的氧化鋅奈米柱陣列，使奈米柱的側向尺寸從50奈米增加至200~400奈米，最多增加了8倍之多，長度也從原本的500奈米增加至1830奈米。

關鍵字

水熱法 ； 氧化鋅奈米柱 ； 氧化鋅薄膜 ； 溶膠凝膠法 ； 退火

並列摘要

The study of this thesis is to investigate how to apply the hydrothermal method to fabricate well-oriented and high-quality zinc oxide micro/nanorods. First, we introduce how to obtain the ZnO thin films prepared by sol-gel method and hydrothermally prepared ZnO micro/nanorods. Then we discussed the effects of annealing process on ZnO thin films and ZnO nanorods. After that, we pre-coated a gold thin film on ZnO thin film before annealing and successfully improved the orientation and size of ZnO micro/nanorods. Finally, we discussed the change of the existing LED structure, and to grow ZnO micro/nanorods on GaN substrate and approached selected growth.

Through the experiment, we find that the ZnO thin film can form bigger ZnO crystal when annealed at around 900°C. In order to grow a large ZnO rod, ZnO sol-gel thin film has to anneal at high temperatures to form a big grain. At the same time, the big grain causes random growth of nanorods. In this work, we demonstrate a new method by annealing a pre-coated thin metal film on a ZnO sol-gel seed layer to obtain a smooth seed layer to grow vertical, well-aligned, and large ZnO rods. We also do the XRD analysis, the peaks in the x-ray diffraction patterns are indexed to the hexagonal phase of ZnO. With the gold-coating treatment, only a very strong (002) diffraction peak is observed, indicating that the ZnO sample has a high c-axis orientation. The PL spectrum of the ZnO nanorods shows the intensity of the green emission for the ZnO rods on the seed layer with pre-coated gold treatment was much weaker than that of the ZnO rods on the normal ZnO seed layer. It shows that the ZnO rods on the smooth seed layer have a better crystallization than the others. The EDS spectra reveal the presence of Zn and O elements, confirming that there is no residual gold on the sample and that the nanowire arrays are primarily ZnO.
The function of coating a thin metal film on a sol-gel ZnO-seed-coated substrate by using an E-gun before doing the annealing treatment is to inhibit the formation of ZnO crystals and let the crystallization occur along the x-y plane instead of growing along the c-axis direction during the annealing process. Next, the smooth seed layer also grows the ZnO nanorods through a hydrothermal method. We see the ZnO nanorods with good orientation along the c-axis and improved rod size and the lateral rod size is about 200~400nm and the rod length is up to 1830nm.

並列關鍵字

Hydrothermal ； ZnO micro/nanorods ； ZnO thin films ； sol-gel method ； annealing

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