探討銀奈米粒子吸附於氧化鋅奈米柱之場發射元件與氣體感測元件特性分析

The study of zinc oxide nanorods gas sensor and field emission with adsorbed silver nanoparticles

王璨華(Tsan-Hua Wang)

指導教授 ： 楊勝州

國立虎尾科技大學/電機資訊學院/電子工程系碩士班/碩士(2016年)

摘要

氧化鋅是一種便宜又實用的Ⅱ-Ⅵ族材料，利用銀奈米粒子吸附於氧化鋅上，其目的是提升氧化鋅自身的光電特性，在此篇製備氧化鋅奈米柱的方式採用了水溶液法製造，接著使用硝酸銀水溶液以浸泡的方式，使銀奈米粒子吸附於製備完成的氧化鋅奈米柱上，再以熱退火的方式完成元件。
最後使用儀器量測其表面(SEM)、元素含量(EDS)、光學特性(PL)、結晶性(XRD)以及(TEM)，電特性部份則分析場發射特性以及其氣體感測元件特性分析。
表面會多出銀奈米粒子的形貌，且在元素含量(EDS)中發現1.28%銀的含量，這代表了銀奈米粒子有確實吸附於氧化鋅奈米柱表面上，並在(TEM)中進一步證實銀奈米粒子的吸附，其銀奈米粒子直徑為18nm~95nm，並在結晶性(XRD)沿著(002)方向生長可看出氧化鋅六角纖鋅礦結構。
光學特性(PL)顯示了氧化鋅本身380nm的發光波段，還有其氧缺陷引起的可見光發光波段550nm，可進一步證明氧化鋅奈米柱的結構良好，接著在場發射特性上其turn-on電場為2.5V/μm，增強因子為2007，比原先未吸附銀奈米粒子的氧化鋅奈米柱，其turn-on電場為3.2V/μm，增強因子為748更佳良好，這代表了吸附銀奈米粒子於氧化鋅奈米柱提升了其場發特性，有利於應用於其他元件上。
最後在氣體感測特性方面，在不同量測氣體濃度以及不同量測環境溫度下 兩者皆表現了不同的特性，在不同溫度下，CO2濃度對氧化鋅奈米柱以及吸附銀奈米粒子之氧化鋅奈米柱其靈敏度隨著溫度升高而升高，從15%上升至23%而在吸附銀奈米粒子之氧化鋅奈米柱則是35%上升至45%，因此當操作溫度升高及二氧化碳濃度增加時，感測元件之靈敏度會提升，因此水熱法可快速製作高氣敏性氧化鋅薄膜之二氧化碳氣體感測元件，且兼具大面積生產及低成本優勢。

關鍵字

銀奈米粒子 ； 氧化鋅奈米柱 ； 場發射 ； 水熱法 ； 二氧化碳氣體感測元件

並列摘要

Zinc oxide is low-cost and practical Ⅱ-Ⅵ chemical materials, which utilized to absorb silver nanoparticle on zinc oxide. It can improve the electrical characteristics of the zinc oxide. In this paper, ZnO nanorods is prepared via hydrothermal method and use silver nitrate solution to absorb silver nanoparticle on ZnO nanorods. Finally, the characteristic surface morphology (SEM) observation of instrumental analysis, crystal(XRD), optical properties(PL), element content(EDS), (TEM) and measurement field emission. The results indicate that ZnO nanorods which have an average diameter and maximum length of around 35nm~75nm and 2.14μm, respectively. It was found that the silver nanoparticle on ZnO nanorods, and silver nanoparticle have an average diameter of around 18nm~95nm. The existence of Ag was examined by energy diffraction spectra (EDS). The structural characteristics of the ZnO were measured by X-ray diffraction (XRD). It was found that the peaks related to the wurtzite structure ZnO (002), (102), (103), and (112) diffraction peaks, the (002) peak indicates that the nanorods were preferentially oriented in the c-axis direction. The PL spectra of all the samples were shown in two emission bands, ultraviolet (UV) and visible (blue and green) bands, were observed in each spectrum. The UV emission is always ascribed to the band gap of ZnO, and the strong visible emission centered at around 500 nm is assigned to the defects (such as oxygen vacancies and interstitial zinc) in ZnO. It was also found that the turn-on electrical field reduced from 3.2 to 2.5 V/μm and the field enhancement factor enhanced from 748 to 2007.In the results with an operating temperature, the sensitivities of the ZnO nanorods and absorb silver nanoparticle on ZnO nanorods gas sensors were about 15% to 23%, and 35% to 45%, respectively.Hence, the sensitivity and response presented good performance at increasing operating temperatures and CO2 concentrations. The hydrothermal method was successfully applied for making ZnO gas sensors with large-scale production and low cost.

並列關鍵字

silver nanoparticle ； ZnO nanorods ； field emitter ； CO2 gas sensors

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