本文選題：脈沖激光沉積 + 磁控濺射��； 參考：《吉林大學(xué)》2014年博士論文

【摘要】：氧化鎘(CdO)是屬于II-VI族的一種直接窄帶隙n型半導(dǎo)體氧化物，在常溫下具有立方NaCl晶體結(jié)構(gòu)。CdO薄膜本身具有大量的本征點(diǎn)缺陷，如氧空位(Vo)和鎘間隙原子(Cdi)等缺陷，它們作為淺施主為CdO提供了大量的載流子，使其具有較低的電阻率(10-3~10-4Ω cm)。CdO的禁帶寬度(Eg)為2.2eV，對(duì)應(yīng)的波長(zhǎng)為550nm，位于太陽光譜在可見光波段能量最強(qiáng)值510nm附近。因此，CdO以其高載流子濃度、低電阻率、可見光區(qū)域高透過率等特點(diǎn)，被廣泛的應(yīng)用于透明電極、太陽能電池、光電晶體管和氣敏傳感器等領(lǐng)域。然而，CdO的禁帶寬度過窄極大地限制了其在光電器件領(lǐng)域的應(yīng)用。為了與其它TCOs薄膜競(jìng)爭(zhēng)，在提高CdO的電學(xué)性能的同時(shí)，通過摻雜其它元素或調(diào)解工藝參數(shù)增加其禁帶寬度來提高薄膜在可見光波段的透過率范圍，改善其光學(xué)性能。 本論文對(duì)CdO薄膜的光學(xué)、電學(xué)和氣敏性等性質(zhì)進(jìn)行了系統(tǒng)的總結(jié)，詳細(xì)介紹了CdO的各種實(shí)際應(yīng)用和制備方法，同時(shí)對(duì)CdO薄膜的研究方向進(jìn)行了展望。采用磁控濺射法和脈沖激光沉積技術(shù)制備CdO基薄膜，通過調(diào)節(jié)化學(xué)計(jì)量比或摻雜過渡元素、稀土元素(Gd、Ce、In)等途徑來制備導(dǎo)電性好、可見光區(qū)域透過率高的透明CdO薄膜。在此基礎(chǔ)上，將Gd和In摻雜的CdO薄膜沉積在p-Si上制備異質(zhì)結(jié)太陽能薄膜電池并研究其電學(xué)性能，探究CdO基薄膜作為太陽能薄膜電池的可能性。使用單束飛秒激光技術(shù)在CdO薄膜表面誘導(dǎo)出周期納米條紋結(jié)構(gòu)，并將該微型結(jié)構(gòu)薄膜制成CdO/p-Si異質(zhì)結(jié)。我們希望這些研究能夠拓展CdO納米材料在光電器件和太陽能薄膜電池等領(lǐng)域的應(yīng)用。利用X射線衍射儀(XRD)、X射線光電子能譜(XPS)、衍射透射電子顯微鏡(TEM)、高倍透射電子顯微鏡(HRTEM)、場(chǎng)發(fā)射掃描電子顯微鏡(FE-SEM)及場(chǎng)發(fā)射掃描電子顯微鏡配套的能譜儀(EDS)對(duì)薄膜的成分和微觀組織進(jìn)行了分析和觀察；利用紫外-可見光分光光度計(jì)(UV-VIS)、霍爾效應(yīng)儀(Hall)對(duì)薄膜的光學(xué)和電學(xué)性能進(jìn)行了表征；采用電流-電壓(I-V)伏安特性曲線對(duì)異質(zhì)結(jié)的電學(xué)性能進(jìn)行了表征。具體的實(shí)驗(yàn)內(nèi)容和結(jié)果如下： 1.利用脈沖激光沉積法(PLD)在普通玻璃襯底上制備未摻雜CdO薄膜，氧氣氣氛壓強(qiáng)為10Pa，襯底溫度為室溫(25℃)，靶材為純度99.99%CdO粉末制備的陶瓷靶。研究了不同脈沖激光能量密度(10~25J/cm2)下獲得的CdO薄膜的晶體結(jié)構(gòu)、光學(xué)和電學(xué)性能影響。結(jié)果表明所有薄膜為多晶CdO立方晶體結(jié)構(gòu)，沿著[200]方向高度擇優(yōu)生長(zhǎng)。隨著激光能量密度的下降，薄膜的平均晶粒尺寸變化較大，由108.3nm變?yōu)?1.1nm。晶粒尺寸的不斷減小使得薄膜應(yīng)力增加并導(dǎo)致薄膜表面Cd和O原子擴(kuò)散速率改變，薄膜內(nèi)以氧空位(Vo)為主的缺陷逐漸增多，而這些缺陷能級(jí)使得本征CdO薄膜的自由電子濃度增加。擁有最小晶粒尺寸的CdO薄膜在可見光區(qū)域內(nèi)具有高的光學(xué)透過率(~92%)，明顯變寬的禁帶寬度(3.33eV)，高的載流子濃度(1.25×1021cm-3)和低的電阻率(2.8×10-4cm)。使得該實(shí)驗(yàn)方法和工藝條件下制備的晶粒尺寸較小的CdO薄膜在太陽能電池、透明薄膜電極和其它光電子設(shè)備具有廣泛的應(yīng)用前景。 2.通過射頻磁控濺射法(RFMS)在普通玻璃襯底上沉積了鈰(Ce)和釓(Gd)共摻雜氧化鎘透明導(dǎo)電薄膜。氣體氣氛總壓強(qiáng)為10Pa，其中氬氣(Ar)氣體流量為40sccm，氧氣(O2)氣體流量為10sccm，襯底溫度為400℃，靶材為純度99.99%的CdO、CeO2和Gd2O3粉末充分混合制備的陶瓷靶。研究了不同Ce和Gd含量對(duì)CdO薄膜晶體結(jié)構(gòu)、光學(xué)和電學(xué)性能的影響。Ce和Gd的摻雜促進(jìn)所有薄膜沿[200]方向的擇優(yōu)生長(zhǎng)，(200)晶面衍射角(θ)逐漸變小，晶格常數(shù)(a)逐漸變大。0.4at.%Ce和0.8at.%Gd摻雜的薄膜具有最佳的光電學(xué)性能，在可見光區(qū)域內(nèi)具有高的光學(xué)透過率(~85%)，光學(xué)禁帶寬度增大為2.99eV，電阻率達(dá)到最小值3.3×10-4Ω cm。當(dāng)Ce和Gd的摻雜含量進(jìn)一步增加到0.5at.%和1.0at.%時(shí)，晶界散射和電離雜質(zhì)散射作用的增強(qiáng)導(dǎo)致薄膜的光學(xué)和電學(xué)性能下降。因而，適當(dāng)?shù)腃e和Gd摻雜能夠改善CdO薄膜的光學(xué)和電學(xué)性能，使其在透明導(dǎo)電材料方面具有重要的應(yīng)用價(jià)值。 3.通過脈沖激光法(PLD)在石英玻璃基底上沉積了釓(Gd)和銦(In)共摻雜氧化鎘透明導(dǎo)電薄膜。氧氣氣氛壓強(qiáng)為10Pa，襯底溫度為200℃，靶材為純度99.99%的CdO、In2O3和Gd2O3粉末充分混合制備的陶瓷靶。XRD分析證實(shí)所有薄膜具有立方NaCl晶體結(jié)構(gòu)，具有高度(200)擇優(yōu)取向。而XPS分析表明In的摻雜導(dǎo)致了In2O3相的出現(xiàn)。隨著Gd和In的摻雜含量的不斷增加，薄膜的晶粒尺寸由40nm逐漸減小為23nm。所有薄膜在可見光范圍內(nèi)都有很高的透過率(~85%)。尤其是2at.%Gd和4at.%In摻雜的CdO薄膜在可見光波段的透過率高達(dá)92%，其相應(yīng)的禁帶寬度為3.56eV。在相同實(shí)驗(yàn)條件下，將這些薄膜沉積在p-Si襯底上制得p-n異質(zhì)結(jié)。樣品的I-V特性曲線表明實(shí)驗(yàn)制得的異質(zhì)結(jié)具有二極管特性，而且在光照條件下表現(xiàn)出了明顯的光伏效應(yīng)。3at.%Gd和6at.%In摻雜的CdO薄膜表現(xiàn)出最佳的光伏特性。其光電轉(zhuǎn)換效率達(dá)到了7.5%，填充因子為63%，飽和電流密度(Jsc)和開路電壓(Voc)分別為11.4mA/cm2和1.04V。實(shí)驗(yàn)結(jié)果表明摻雜Gd和In的CdO薄膜在太陽能薄膜電池方面具備潛在應(yīng)用價(jià)值。 4.利用脈沖激光沉積法(PLD)在普通玻璃襯底上制備未摻雜CdO薄膜，氧氣氣氛壓強(qiáng)為10Pa，襯底溫度為25℃。將制得的薄膜在馬弗爐里進(jìn)行退火處理，退火溫度和退火時(shí)間分別為200℃和30min。使用單光束飛秒激光脈沖在CdO薄膜表面上采用不同的脈沖重復(fù)頻率進(jìn)行周期納米條紋結(jié)構(gòu)誘導(dǎo)。輸出激光脈沖的中心波長(zhǎng)為800nm，脈沖寬度為100fs，重復(fù)頻率為1~2500Hz可調(diào)，，單脈沖能量為2mJ。由FE-SEM觀察可知，經(jīng)過2000個(gè)脈沖數(shù)照射后，CdO薄膜表面出現(xiàn)短周期條紋微型結(jié)構(gòu)，條紋周期為150~170nm。當(dāng)脈沖數(shù)大于2000時(shí)，CdO表面開始出現(xiàn)蓬松的納米泡沫的微型結(jié)構(gòu)。配套積分球的UV-VIS測(cè)試表明具有飛秒激光微型結(jié)構(gòu)的CdO薄膜具有寬頻高吸收的特性。而Hall效應(yīng)測(cè)試表明，當(dāng)脈沖數(shù)為2000時(shí)，CdO薄膜獲得最高的載流子濃度為1.9×1021cm-3和最低電阻率為1.3×10-5Ωcm。在此基礎(chǔ)上，利用飛秒激光微型結(jié)構(gòu)薄膜來制備的CdO/p-Si異質(zhì)結(jié)，在暗態(tài)和光照兩種環(huán)境下均表現(xiàn)出良好的整流特性。光照條件I-V特性曲線表明異質(zhì)結(jié)具有光伏特性，測(cè)得最佳的太陽能電池開路電壓Voc為0.55V，短路電流Jsc為6.8mA/cm2，填充因子為29.1%，轉(zhuǎn)換效率為1.1%。飛秒激光微型結(jié)構(gòu)薄膜的寬頻高吸收特性使其在很多的光電器件領(lǐng)域，如光伏器件、電荷藕合器件和光探測(cè)器等具有潛在的應(yīng)用前景。
[Abstract]:Cadmium oxide (CdO) is a direct narrow band gap n type semiconductor oxide which belongs to the II-VI family. The.CdO thin film with cubic NaCl crystal structure at normal temperature has a large number of intrinsic point defects, such as oxygen vacancy (Vo) and cadmium gap atom (Cdi), which provide a large number of carriers for the shallow donor for CdO, and make it have a lower resistivity. The forbidden band width (Eg) of (10-3~10-4 Omega cm).CdO is 2.2eV and the corresponding wavelength is 550nm, located near the maximum energy value of the solar spectrum in the visible light band. Therefore, CdO is widely used in transparent electrodes, solar cells, phototransistors and gas sensitive transmission with its high carrier concentration, low resistivity and high transmittance in visible light region. However, the narrow band width of CdO restricts its application in the field of optoelectronic devices. In order to compete with other TCOs films, in order to improve the electrical properties of CdO, increase the band gap by doping other elements or mediation process parameters to improve the transmittance range of the thin film in the visible light band and improve its light. Learning performance.
In this paper, the properties of optical, electrical and gas sensitivity of CdO films are systematically summarized. Various practical applications and preparation methods of CdO are introduced in detail. At the same time, the research direction of CdO films is prospected. CdO based films are prepared by magnetron sputtering and pulsed laser deposition, by adjusting the stoichiometric ratio or doping transition element. Gd, Ce, In, etc. are used to prepare transparent CdO thin films with good conductivity and high transmittance in visible region. On this basis, Gd and In doped CdO films are deposited on p-Si to prepare heterojunction solar thin film batteries and their electrical properties are studied. The possibility of the CdO based thin film as a solar thin film battery is explored. Single beam flight is used. Second laser technology induces the periodic nanoscale stripe structure on the surface of the CdO film, and makes the microstructural thin film into CdO/p-Si heterojunction. We hope that these studies can expand the application of CdO nanomaterials in the fields of photoelectric devices and solar thin film batteries. Using X ray diffractometer (XRD), X ray photoelectron spectroscopy (XPS), diffraction transmission electricity The composition and microstructure of the films were analyzed and observed by TEM, HRTEM, field emission scanning electron microscopy (FE-SEM) and field emission scanning electron microscopy (EDS). The optical and electrical properties of the films were used by ultraviolet visible Photometer (UV-VIS) and Holzer effect instrument (Hall). The properties were characterized, and the electrical properties of the heterojunction were characterized by the current voltage (I-V) volt ampere characteristic curve. The specific experimental contents and results were as follows:
1. the amorphous CdO film was prepared by pulsed laser deposition (PLD) on the ordinary glass substrate. The oxygen atmosphere pressure was 10Pa, the substrate temperature was room temperature (25 C) and the target was prepared by the purity of 99.99%CdO powder. The crystal structure, optical and electrical properties of the CdO film obtained under different pulse laser energy density (10~25J/cm2) were studied. The results show that all the thin films are polycrystalline CdO cubic crystal structure, and the growth of the average grain size is higher along the [200] direction. With the decrease of the laser energy density, the average grain size of the thin film varies greatly. The decrease of the grain size from 108.3nm to the 21.1nm. grain size makes the film stress increase and lead to the change of the Cd and O atom diffusion rate on the surface of the film. The defects of the oxygen vacancy (Vo) in the film increase gradually, and these defect levels increase the free electron concentration of the intrinsic CdO film. The CdO thin films with the smallest grain size have high optical transmittance (~92%) in the visible region, the broadened band gap (3.33eV), high carrier concentration (1.25 x 1021cm-3) and low resistance. The rate (2.8 x 10-4cm) makes the CdO thin films with smaller grain size prepared under the experimental and technological conditions have a wide application prospect in solar cells, transparent thin film electrodes and other photoelectron devices.
2. Ce and gadolinium (Gd) Co doped transparent conductive film are deposited on ordinary glass substrates by RF magnetron sputtering (RFMS). The total pressure of gas atmosphere is 10Pa, in which the gas flow rate of argon (Ar) is 40sccm, oxygen (O2) gas flow is 10sccm, the substrate temperature is 400, the target is 99.99% CdO, CeO2 and Gd2O3 powder is fully mixed. The effects of the content of different Ce and Gd on the crystal structure, optical and electrical properties of CdO films are studied. The doping of.Ce and Gd promotes the preferred growth of all thin films along [200] direction. (200) the diffraction angle of the crystal (theta) becomes smaller and the lattice constant (a) gradually becomes larger in.0.4at.%Ce and 0.8at.%Gd doped films. It is possible to have high optical transmittance (~85%) in the visible light region, the width of optical band gap is increased to 2.99eV, the resistivity is 3.3 x 10-4 Omega cm., when the doping content of Ce and Gd is further increased to 0.5at.% and 1.0at.%, the enhancement of the grain boundary scattering and the enhancement of ionizing impurity scattering leads to the decrease of the optical and electrical properties of the film. The doping of Ce and Gd can improve the optical and electrical properties of CdO thin films, and make them have important application value in transparent conductive materials.
3. the transparent cadmium oxide film Co doped with gadolinium (Gd) and indium (In) was deposited on the quartz glass substrate by pulsed laser method (PLD). The oxygen atmosphere pressure was 10Pa, the substrate temperature was 200, the target material was 99.99% CdO, and the In2O3 and Gd2O3 powder fully mixed with the ceramic target.XRD confirmed that all the thin films had cubic NaCl crystal structure. The XPS analysis shows that the doping of In leads to the appearance of In2O3 phase. With the increase of the doping content of Gd and In, the grain size of the thin film gradually decreases from 40nm to the high transmittance (~85%) in the visible light range of all the 23nm. films (~85%), especially the CdO film doped with 2at.%Gd and 4at.%In in visible light. The transmittance of the band is up to 92%, and the corresponding band gap is 3.56eV. under the same experimental conditions. These films are deposited on the p-Si substrate to produce p-n heterojunction. The I-V characteristic curve of the sample shows that the experimental heterojunction has a diode characteristic, and the apparent photovoltaic effect of.3at.%Gd and 6at.%In is displayed under the light condition. The hybrid CdO film shows the best photovoltaic characteristics. The photoelectric conversion efficiency is 7.5%, the filling factor is 63%, the saturation current density (Jsc) and the open circuit voltage (Voc) are 11.4mA/cm2 and 1.04V. respectively. The results show that the CdO thin films doped with Gd and In are potential applications of the solar thin film battery mask.
4. using pulse laser deposition (PLD) to prepare the undoped CdO film on the ordinary glass substrate, the oxygen atmosphere pressure is 10Pa and the substrate temperature is 25. The annealed film is annealed in the muffle furnace. The annealing temperature and the annealing time are 200 and 30min. using single beam femtosecond laser pulse on the surface of the CdO film. The pulse repetition frequency is induced by the periodic nanoscale fringe structure. The central wavelength of the output laser pulse is 800nm, the pulse width is 100fs, the repetition rate is 1~2500Hz, and the single pulse energy is 2mJ. by FE-SEM. After 2000 pulses, the surface of the CdO film shows a short periodic fringes micro structure, the fringe period is 150~170n M. when the number of pulses is greater than 2000, the micro structure of a fluffy nano foam begins to appear on the CdO surface. The UV-VIS test of the supporting integral ball shows that the CdO film with a femtosecond laser micro structure has the characteristics of wide frequency and high absorption. The Hall effect test shows that the highest carrier concentration of the CdO film is 1.9 x 1021cm-3 when the number of pulses is 2000. On the basis of the minimum resistivity of 1.3 x 10-5 Omega cm., the CdO/p-Si heterojunction prepared by the femtosecond laser micro structure film shows good rectifying characteristics under the dark and light conditions. The I-V characteristic curve of the illumination condition shows that the heterojunction has the photovoltaic characteristics and the optimum open circuit voltage of the solar cell is Voc 0.55V, The short circuit current Jsc is 6.8mA/cm2, the filling factor is 29.1%. The wide frequency and high absorption characteristic of the 1.1%. femtosecond laser micro structure film makes it have potential applications in many optoelectronic devices, such as photovoltaic devices, charge coupling devices and photodetectors.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TB383.2

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