AZO透明导电薄膜光电性能的研究进展

掺铝氧化锌(AZO)薄膜其原料来源广、经济无毒,且具有优越的光电性能,可以与传统铟锡氧化物(ITO)薄膜相媲美,是优良的透明导电材料。目前,关于各制备工艺参数对AZO薄膜的影响规律及其影响机理仍是研究热点。综述了透明导电AZO薄膜光学与电学性能的研究进展,讨论了各制备工艺条件对薄膜性能的影响,分析了AZO/metal/AZO多层膜的研究现状,并对AZO薄膜的研究方向给予了展望。     

磁控溅射制备AZO/Ag/AZO透明导电膜的性能研究

选择ZnO2与Al2O3质量比为97：3的靶材为溅射源,用射频磁控溅射法室温下在玻璃基底上沉积AZO／Ag／AZO薄膜,讨论了氧流量变化对薄膜透光率、方阻及表面形貌的影响并深入分析了机理。研究结果表明,氧流量变化会导致薄膜沉积厚度的变化,氧流量为4时薄膜沉积速率最快。沉积AZO时充入氧气会使整个膜系的透光率不随Ag层增厚明显降低,并且会使膜系的方阻降低。在最优氧流量为4L／min（标准状态下,下同）上下各沉积59nm的AZO与氧流量为0时沉积33nm银层相匹配的复合膜在可见光区（包括基底）的透光率达到90％,方阻为2．5Ω/□。     

透明导电AZO/Cu双层薄膜制备及其性能

采用直流磁控溅射方法在玻璃衬底上室温生长了AZO/Cu双层薄膜,Cu层厚度控制在9nm,研究了AZO层厚度对薄膜电学和光学性能的影响。当AZO层厚度为20～80nm时,AZO/Cu双层薄膜具有良好的综合光电性能,方块电阻为12～14Ω/sq,可见光平均透过率为70～75%,品质因子为2×10-3～5×10-3Ω-1。AZO/Cu双层薄膜可以观察到Cu（111）和ZnO（002）的XRD衍射峰。通过退火研究表明,AZO/Cu双层薄膜的光电性能可在400℃下保持稳定,具有良好的热稳定性。本研究制备的透明导电AZO/Cu双层薄膜具有室温制程、综合光电性能良好、结晶性能较好、稳定性高的优点,可以广泛应用于光电器件透明电极及镀膜玻璃等领域。     

薄膜厚度和工作压强对室温制备AZO薄膜性能的影响

采用射频磁控溅射法在室温下、普通玻璃基片上制备了AZO透明导电薄膜。用X射线衍射仪、原子力显微镜、紫外-可见分光光度计和四探针测量了不同薄膜厚度和不同工作压强下所得样品的结构、电学和光学性能,结果表明,所制备的AZO薄膜均具有六角纤锌矿结构,沿c轴择优取向生长;在可见光范围内,薄膜平均透过率约为80%;随着薄膜厚度的增加和工作压强的降低,薄膜的电阻率呈下降趋势;得到的薄膜最低方块电阻为7.5Ω/□。     

AZO薄膜用于GaN基LED透明电极的性能研究

采用脉冲激光沉积法制备了Al掺杂ZnO(AZO)薄膜, 研究了不同沉积氧压下薄膜的光电性能。当沉积压强为0.1 Pa时, AZO薄膜光电性能最优。将该薄膜用于GaN基LED透明电极作为电流扩展层, 在20 mA正向电流下观察到了520 nm处很强的芯片发光峰, 但芯片工作电压较高, 约为10 V, 芯片亮度随正向电流的增大而增强。二次离子质谱测试表明, AZO薄膜与GaN层界面处两种材料导电性能的变化以及钝化层的形成是导致芯片工作电压偏高的原因。     

CCP/ICP混合放电C4F8/Ar等离子体高、低频功率对AZO薄膜绒面效果的影响

室温下,采用射频磁控溅射方法在石英基片上制备掺铝氧化锌(AZO)透明导电薄膜。利用CCP/ICP混合放电C4F8/Ar等离子体对制得的AZO薄膜进行绒面处理。利用原子力显微镜(AFM)对薄膜表面形貌进行表征,利用光纤光谱仪分析放电产生的碳氟基团含量的变化。实验结果发现低频功率的增大能够有效增加等离子体中F原子的含量,进而提高薄膜的刻蚀效果,获得较好的绒面结构;但是高频功率变化对薄膜刻蚀效果影响较小。     

PET纤维基AZO透明导电薄膜溅射工艺参数的优化

室温下,结合正交实验表,用射频磁控溅射在涤纶(PET)非织造布基材上生长AZO(Al2O3:ZnO)纳米结构薄膜.采用四探针测量仪测试AZO薄膜的方块电阻,用原子力显微镜(AFM)分析薄膜微结构;通过正交分析法对实验L9(33)AZO薄膜的性能指标进行分析.实验结果表明:溅射厚度对AZO薄膜导电性能起主导作用,其次为氩气压强和溅射功率;同时,得出制备AZO薄膜的最佳工艺为:溅射功率150W、厚度100m和气压0.2Pa,该参数下样品的方块电阻为1.633×103Ω,AZO纳米颗粒的平均直径约为69.4nm.     

AZO透明导电薄膜的制备技术及应用进展

概述了国内外AZO透明导电薄膜的多种制备技术和开发应用进展。详细介绍了磁控溅射、溶胶-凝胶、脉冲激光沉积、真空蒸镀、化学气相沉积等工艺在AZO薄膜制备中的研究现状,并且在对AZO膜与ITO膜性能比较的基础上,指出AZO薄膜的产业化前景好。     

银基透明导电薄膜制备及其性能研究

采用磁控溅射方法制备了ZnO/Ag/ZnO、AZO/Ag/AZO三层和AZO/LiF/Ag/LiF/AZO、AZO/Al/Ag/Al/AZO五层透明导电薄膜,该体系薄膜450~700 nm的平均透过率在80%以上,方块电阻约5Ω/sq。插入LiF和Al的AZO/LiF/Ag/LiF/AZO和AZO/Al/Ag/Al/AZO导电薄膜在723 K退火后方块电阻分别为5.7Ω/sq和7.6Ω/sq,而AZO/Ag/AZO薄膜电阻快速上升到27Ω/sq。这表明五层结构的透明导电薄膜相比三层结构的导电薄膜明显的提高了热稳定性。可能原因是插入的LiF或Al层能抑制Ag原子的扩散和团聚。     

室温下高速沉积AZO薄膜的研究

在室温下,采用射频磁控溅射技术以较大的功率密度(7W/cm2)沉积了一系列掺铝氧化锌(AZO)透明导电薄膜,探索了溅射压强对沉积速率及薄膜性能的影响。结果表明,当工作压强为2.0Pa时,高速(67nm/min)沉积得到的薄膜的电阻率为2.63×10-3Ω.cm,可见光平均透过率为83%,并且在薄膜表面有一定的织构。     

Improving efficiency of organic light-emitting diodes fabricated utilizing AZO/Ag/AZO multilayer electrode

Multilayer transparent electrode based on Al-doped zinc oxide (AZO)/Ag/Al-doped zinc oxide (AZO) was fabricated by sputtering, and a green organic light-emitting diode (OLED) device utilizing AZO/Ag/AZO as anode was fabricated. The AZO/Ag/AZO multilayer film exhibited superior square resistance and optical transmittance to those of commercial indium tin oxide (ITO). In comparison with the green OLEDs based on ITO and pure AZO anode, the green OLED based on AZO/Ag/AZO showed the highest light-emitting efficiency. The results indicate that AZO/Ag/AZO multilayer electrodes are a promising low-cost, low-toxic and low-temperature processing electrode scheme for OLED application.     

Structural, optical and electrical properties of AZO/Cu/AZO tri-layer films prepared by radio frequency magnetron sputtering and ion-beam sputtering

Highly conducting tri-layer films consisting of a Cu layer sandwiched between Al-doped ZnO (AZO) layers (AZO/Cu/AZO) were prepared on glass substrates at room temperature by radio frequency (RF) magnetron sputtering of AZO and ion-beam sputtering of Cu. The tri-layer films have superior photoelectric properties compared with the bi-layer films (Cu/AZO, AZO/Cu) and single AZO films. The effect of AZO thickness on the properties of the tri-layer films was discussed. The X-ray diffraction spectra show that all films are polycrystalline consisting of a Cu layer with the cubic structure and two AZO layers with the ZnO hexagonal structure having a preferred orientation of (0 0 2) along the c-axis, and the crystallite size and the surface roughness increase simultaneously with the increase of AZO thickness. When the AZO thickness increases from 20 to 100 nm, the average transmittance increases initially and then decreases. When the fixed Cu thickness is 8 nm and the optimum AZO thickness of 40 nm was found, a resistivity of 7.92 × 10⁻⁵ Ω cm and an average transmittance of 84% in the wavelength range of visible spectrum of tri-layer films have been obtained. The merit figure (F_TC) for revaluing transparent electrodes can reach to 1.94 × 10⁻² Ω⁻¹.     

Optimization of ZnO:Al/Ag/ZnO:Al structures for ultra-thin high-performance transparent conductive electrodes

Al-doped ZnO (AZO)/Ag/AZO multilayer coatings (50-70 nm thick) were grown at room temperature on glass substrates with different silver layer thickness, from 3 to 19 nm, by using radio frequency magnetron sputtering. Thermal stability of the compositional, optical and electrical properties of the AZO/Ag/AZO structures were investigated up to 400 °C and as a function of Ag film thickness. An AZO film as thin as 20 nm is an excellent barrier to Ag diffusion. The inclusion of 9.5 nm thin silver layer within the transparent conductive oxide (TCO) material leads to a maximum enhancement of the electro-optical characteristics. The excellent measured properties of low resistance, high transmittance in the visible spectral range and thermal stability allow these ultra-thin AZO/Ag/AZO structures to compete with the 1 μm thick TCO layer currently used in thin film solar cells.     

Effect of Cu layer thickness on the structural, optical and electrical properties of AZO/Cu/AZO tri-layer films

Highly conducting AZO/Cu/AZO tri-layer films were successfully deposited on glass substrates by RF magnetron sputtering of Al-doped ZnO (AZO) and ion-beam sputtering of Cu at room temperature. The microstructures of the AZO/Cu/AZO multilayer films were studied using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and atomic force microscope (AFM). X-Ray diffraction measurements indicate that the AZO layers in the tri-layer films are polycrystalline with the ZnO hexagonal structure and have a preferred orientation with the c-axis perpendicular to the substrates. With the increase of Cu thickness, the crystallinity of AZO and Cu layers is simultaneously improved. When the Cu thickness increases from 3 to 13 nm, the resistivity decreases initially and then varies little, and the average transmittance shows a first increase and then decreases. The maximum figure of merit achieved is 1.94 × 10⁻² Ω⁻¹ for a Cu thickness of 8 nm with a resistivity of 7.92 × 10⁻⁵ Ω cm and an average transmittance of 84%.     

Influence of Ag thickness on electrical, optical and structural properties of nanocrystalline MoO3/Ag/ITO multilayer for optoelectronic applications

In this study, MoO₃/Ag/ITO/glass (MAI) nano-multilayer films were deposited by the thermal evaporation technique and then were annealed in air atmosphere at 200 °C for 1 h. The effects of Ag layer thickness on electrical, optical and structural properties of the MoO₃(45 nm)/Ag(5-20 nm)/ITO(45 nm)/glass nano-multilayer films were investigated. The sheet resistance decreased rapidly with increasing Ag thickness. Above a thickness of 10 nm, the sheet resistances became somewhat saturated to a value of 3(Ω/□). The highest transparency over the visible wavelength region of spectrum (85%) was obtained for 10 nm Ag layer thickness. Carrier mobility, carrier concentrations, transmittance and reflectance of the layers were measured. The allowed direct band-gap for an Ag thickness range 5-20 nm was estimated to be in the range 3.58-3.71 eV. The XRD pattern showed that the films were polycrystalline. X-ray diffraction has shown that Ag layer has a (111) predominant orientation when deposited. The figure of merit was calculated for MAI multilayer films. It has been found that the Ag layer thickness is a very important factor in controlling the electrical and optical properties of MAI multilayer films. The optimum thickness of the Ag layer for these films was determined. The results exhibit that the MAI transparent electrode is a good structure for use as the anode of optoelectronic devices.     

Electrical,optical, and structural properties of thin films with tri-layers of AZO/ZnMgO/AZO grown by filtered vacuum arc deposition

Transparent conductive oxides (TCO) are indispensable as front electrode for most of thin film electronic devices such as transparent electrodes for flat panel displays, photovoltaic cells, windshield defrosters, transparent thin film transistors, and low emissivity windows. Thin films of aluminum-doped zinc oxide (AZO) have shown to be one of the most promising TCOs. In this study, three layered Al-doped ZnO (AZO)/ZnMgO/AZO heterostructures were prepared by filtered cathodic arc deposition (FCAD) on glass substrates. The objective is to find a set of parameters that will allow for improved optical and electrical properties of the films such as low resistivity, high mobility, high number of charge carriers, and high transmittance. We have investigated the effect of modifications in thickness and doping of the ZnMgO inner layer on the structural, electrical, and optical characteristics of the stacked heterostructures.     

Transparent conductive and infrared reflective AZO/Cu/AZO multilayer film prepared by RF magnetron sputtering

AZO/Cu/AZO multilayer films were prepared on glass substrate by radio frequency magnetron sputtering technology. The prepared films were investigated by a four-point probe system, X-ray diffraction, optical transmittance spectra, scanning electron microscope, atomic force microscopy and Fourier transform infrared spectroscopy. The results showed that Cu inner layer started forming a continuous film at the thickness around 11 nm. The prepared AZO/Cu/AZO samples exhibited the visible transmittance of 60–80 % and sample with 15 nm Cu inner layer showed the highest infrared reflection rate of 67 % in FIR region and the lowest sheet resistance of 16.6 Ω/sq. The proper visible transmittance and infrared reflection property of the AZO/Cu/AZO multilayer film make it a promising candidate for future energy conservation materials.     

Effect of ZnO buffer layer on AZO film properties and photovoltaic applications

Aluminum-doped ZnO (AZO) transparent conducting films were deposited on glass substrates with and without intrinsic ZnO (i-ZnO) buffer layers by a home made and low cost radio-frequency (RF) magnetron sputtering system at room temperature in pure argon ambient and under a low vacuum level. The films were examined and characterized for electrical, optical, and structural properties for the application of CIGS solar cells. The influence of sputter power, deposition pressure, film thickness and residual pressure on electrical and optical properties of layered films of AZO, i-ZnO and AZO/i-ZnO was investigated. The optimization of coating process parameters (RF power, sputtering pressure, thickness) was carried out. The effects of i-ZnO buffer layer on AZO films were investigated. By inserting thin i-ZnO layers with a thickness not greater than 125 nm under the AZO layers, both the carrier concentration and Hall mobility were increased. The resistivity of these layered films was lower than that of single layered AZO films. The related mechanisms and plasma physics were discussed. Copper indium gallium selenide (CIGS) thin film solar cells were fabricated by incorporating bi-layer ZnO films on CdS/CIGS/Mo/glass substrates. Efficiencies of the order of 7–8% were achieved for the manufactured CIGS solar cells (4–5 cm² in size) without antireflective films. The results demonstrated that RF sputtered layered AZO/i-ZnO films are suitable for application in low cost CIGS solar cells as transparent conductive electrodes.