本文選題：水熱法 + ZnO:Cd納米棒　； 參考：《重慶師范大學(xué)》2015年碩士論文

【摘要】：ZnO是一種重要的新型半導(dǎo)體金屬氧化物材料,具有壓電、光電特性和高的電荷遷移率等特點(diǎn),被廣泛應(yīng)用于發(fā)光二極管、壓敏器件等領(lǐng)域,在氣敏傳感器和發(fā)光器件方面也有廣泛的應(yīng)用。近年來(lái)許多專(zhuān)家學(xué)者,通過(guò)摻雜其它元素來(lái)改善ZnO氣敏性能和發(fā)光特性,Cd和Zn同屬第二副族,物理化學(xué)性質(zhì)相似,容易實(shí)現(xiàn)Cd替代ZnO中Zn,形成替位摻雜,從而使得ZnO的結(jié)構(gòu)、性質(zhì)發(fā)生改變。Cd摻雜以后使得ZnO的晶粒尺寸減小,帶隙變窄。這對(duì)于研究ZnO氣敏特性和發(fā)光特性具有重要意義。本文主要以六水硝酸鋅(Zn(NO3)2·6H2O)為Zn源,四水硝酸鎘(Cd(NO3)2·4H2O)為Cd源,采用低溫水熱法成功合成了ZnO和ZnO:Cd納米棒(其中Cd/Zn的摩爾比分別為0.01、0.02、0.03、0.04)。通過(guò)X射線衍射儀、場(chǎng)發(fā)射掃描電子顯微鏡和激光共聚焦拉曼光譜儀分別對(duì)樣品的晶體結(jié)構(gòu)、表面形貌和晶體內(nèi)部應(yīng)力進(jìn)行了表征。將制備的樣品均勻旋涂在切割好的玻璃襯底上制成薄膜樣品,利用雙光束紫外/可見(jiàn)/近紅外分光光度計(jì)對(duì)其進(jìn)行透射方面的分析,通過(guò)簡(jiǎn)單計(jì)算進(jìn)而確定其光學(xué)帶隙寬度。利用熒光/磷光發(fā)光分光光度計(jì)對(duì)ZnO及ZnO:Cd納米棒光致發(fā)光特性進(jìn)行研究。探究結(jié)果表明:純的ZnO和不同摻雜濃度的ZnO:Cd納米棒晶體結(jié)構(gòu)均呈六角纖鋅礦,Cd的摻雜使得晶體粒子尺寸減小,ZnO薄膜的光學(xué)帶隙寬度變窄,由分析可得帶隙減小原因有以下兩個(gè)方面:一是在晶體內(nèi)部存在張應(yīng)力。二是在ZnO的帶隙中形成了其它的雜質(zhì)能級(jí)。當(dāng)Cd摻雜量為2%時(shí),我們可以看到樣品存在位于2.67e V的藍(lán)光發(fā)光峰,而這個(gè)峰在其它樣品中并沒(méi)有發(fā)現(xiàn)。通過(guò)分析研究我們得出此藍(lán)光光致發(fā)光峰是由于電子從導(dǎo)帶底到Zn空位(VZn)之間發(fā)生躍遷產(chǎn)生的。從光致發(fā)光峰中我們同樣可以看出由于Cd摻雜增強(qiáng)了ZnO位于2.90e V附近紫光光致發(fā)光峰的強(qiáng)度。利用氣敏測(cè)試裝置對(duì)其氫敏進(jìn)行研究得出:在150℃下,不同摻雜濃度的ZnO:Cd及純ZnO薄膜,當(dāng)氫氣濃度為500ppm時(shí),摻雜濃度為2%時(shí)薄膜的靈敏度最高。對(duì)摻雜濃度為2%的ZnO:Cd薄膜進(jìn)行了不同溫度下測(cè)試得出,當(dāng)溫度達(dá)到80℃時(shí),對(duì)1000ppm氫氣的靈敏度已經(jīng)達(dá)到了2.34。隨著溫度的繼續(xù)增長(zhǎng),靈敏度出現(xiàn)了先增長(zhǎng)后減小的趨勢(shì)。當(dāng)溫度在220℃時(shí)靈敏度已經(jīng)達(dá)到了最大值6.13,響應(yīng)恢復(fù)時(shí)間也比較少。在220℃下對(duì)氫氣進(jìn)行了超靈敏實(shí)驗(yàn)得出,Cd摻雜濃度2%的ZnO:Cd薄膜傳感器件對(duì)氫氣的最小靈敏度為50ppm。在低溫80℃下和220℃下薄膜型氣敏傳感器都具有良好的可重復(fù)性。當(dāng)樣品在空氣中暴露5個(gè)月后,摻雜濃度為2%的ZnO:Cd納米棒比純ZnO的結(jié)構(gòu)更穩(wěn)定。本文研究可以得出ZnO:Cd納米棒對(duì)于發(fā)展藍(lán)紫發(fā)光器件以及開(kāi)發(fā)低溫和超靈敏氫敏器件具有重要的研究意義。
[Abstract]:ZnO is an important new type of semiconductor metal oxide material with the characteristics of piezoelectric, optoelectronic and high charge mobility. It is widely used in light emitting diodes, varistors and other fields. Gas sensors and luminescent devices are also widely used. In recent years, many experts and scholars, by doping other elements to improve the gas sensitivity and luminescence characteristics of ZnO CD and Zn belong to the second secondary family, physical and chemical properties are similar, it is easy to realize CD instead of ZnO, forming substitution doping, thus making the structure of ZnO. The crystal size of ZnO decreases and the band gap becomes narrower after doping with CD. It is of great significance to study the gas sensing and luminescence characteristics of ZnO. In this paper, ZnO and ZnO:Cd nanorods were successfully synthesized by low temperature hydrothermal method with zinc nitrate hexahydrate as Zn source and cadmium nitrate tetrahydrate as CD source. The crystal structure, surface morphology and internal stress of the samples were characterized by X-ray diffractometer, field emission scanning electron microscope and laser confocal Raman spectroscopy, respectively. The prepared samples were evenly spin-coated on the cut glass substrates to make thin film samples. The transmission of the films was analyzed by double beam ultraviolet / visible / near infrared spectrophotometer. The optical band gap width was determined by simple calculation. The photoluminescence characteristics of ZnO and ZnO:Cd nanorods were studied by fluorescence / phosphorescence spectrophotometer. The results show that the crystal structure of pure ZnO and ZnO:Cd nanorods with different doping concentrations are hexagonal wurtzite doping, which makes the crystal particle size decrease and the optical band gap width narrow. The reasons for the decrease of band gap are as follows: one is the existence of tensile stress in the crystal. Second, other impurity energy levels are formed in the band gap of ZnO. When the CD doping amount is 2, we can see that there is a blue luminescence peak at 2.67e V, but this peak is not found in other samples. It is found that the blue photoluminescence peak is due to the transition of electrons from the bottom of the conduction band to the Zn vacancy. It can also be seen from the photoluminescence peak that the intensity of the purple photoluminescence peak of ZnO near 2.90e V is enhanced by CD doping. The hydrogen sensitivity of ZnO:Cd and pure ZnO films with different doping concentration at 150 鈩，

本文編號(hào)：1795884