Properties of transparent conductive ZnO:Al thin films prepared by magnetron sputtering

Middle-frequency alternative magnetron sputtering was used to deposit transparent conductive ZAO (ZnO:Al) thin films with ZAO (98 wt%ZnO+2 wt%Al₂O₃) ceramic target on glass and Si wafers. The influences of the various deposition parameters on the structural, optical and electrical performances of ZAO films have been studied. The structural characteristics of the films were investigated by the X-ray diffractometer and atomic force microscope, while the visible transmittance, carrier concentration and Hall mobility were studied by UV-VIS and the Hall tester, respectively. The lowest resistivity obtained in the work was 4.6×10⁻⁴ Ω cm for the film with average transmittance of 90.0% within the visible wavelength range and sheet resistance of 32 Ω, which was deposited at 250 °C and 0.8 Pa.     

室温下制备的ZnO/Ag/ZnO多层膜的性能

采用射频磁控溅射ZnO陶瓷靶、直流磁控溅射Ag靶的方法在室温下制备了不同厚度的ZnO/Ag/ZnO多层膜。对样品进行了研究。结果表明:随着Ag层厚度的增加,ZnO(002)衍射峰的强度先增加后减小,Ag(111)衍射峰的强度增强,ZnO/Ag/ZnO多层膜的面电阻先减小后趋于稳定。ZnO膜厚度增加,Ag膜易形成晶状结构,ZnO/Ag/ZnO多层膜的透射峰向长波方向移动。ZnO(60nm)/Ag(11nm)/ZnO(60nm)膜在554nm处的透过率高达92.3%,面电阻为4.2?/□,品质常数?TC最佳,约40×10–3/?。     

ZnO/Ag/ZnO多层膜的制备和性质研究

采用射频磁控溅射ZnO陶瓷靶和直流磁控溅射Ag靶的方法制备了ZnO/Ag/ZnO多层膜。用X射线衍射仪、紫外–可见分光光度计、四探针测试仪和金相显微镜对ZnO/Ag/ZnO薄膜的结构、光学透过率、方阻和稳定性进行了研究。结果表明,ZnO(60nm)/Ag/(10nm)/ZnO(60nm)薄膜呈现多晶结构,薄膜在520nm处的光学透过率高达87.5%,方阻Rs为6.2Ω/□。随着顶层ZnO薄膜厚度的增加,ZnO/Ag/ZnO薄膜的稳定性提高。     

Sol-gel-derived ZnO/Cu/ZnO multilayer thin films and their optical and electrical properties

Sol-gel preparation of transparent conducting ZnO/Cu/ZnO multilayer thin films has been investigated. CuO thin films were deposited on glass substrates via a dip-coating method. The CuO thin films were further subjected to reductive annealing in hydrogen to form highly conductive Cu thin films with sheet resistances as low as 10 Ω/□. ZnO/Cu/ZnO multilayers were successfully prepared in a similar way by reducing ZnO/CuO/ZnO. The sheet resistance of the ZnO/Cu/ZnO multilayer thin films is about 10 kΩ/□, which is much higher than that of the pure Cu thin films. The formation of large discrete Cu crystallites in the multilayers explains the poor electrical conductivity of the sol-gel-derived ZnO/Cu/ZnO multilayers.     

Influence of O2/Ar ratio on properties of transparent conductive tantalum-doped ZnO films

Tantalum-doped ZnO transparent conductive films are deposited on glass substrates by radio frequency sputtering at 300°C. The influence of O₂/Ar ratio on the structural, electrical, and optical properties of the as-deposited films is investigated. The lowest resistivity of 4.1 x 10^-4 Vcm is obtained from the film prepared at the O2/Ar ratio of 1/12. The average optical transmittance of the films is over 90%.     

Surface acoustic wave characteristics of ZnO films grown on a polycrystalline 3C-SiC buffer layer

Zinc oxide (ZnO) thin films were deposited onto a polycrystalline (poly) 3C-SiC buffer layer for surface acoustic wave (SAW) applications using a magnetron sputtering system. Atomic force microscopy (AFM) and X-ray diffraction (XRD) showed that the ZnO grown on 3C-SiC/Si had a smooth surface, a dominant c-axis orientation and a lower residual stress in ZnO thin film compared to that grown directly onto Si substrate. In order to evaluate the SAW characteristics of ZnO films on a 3C-SiC buffer layer, the two-port SAW resonators, based on inter-digital transducer (IDT)/ZnO/3C-SiC/Si and IDT/ZnO/Si structures, were fabricated and measured within a temperature range of 25-135 °C. The resulting 3C-SiC buffer layer improved the insertion loss by approximately 7.3 dB within the SAW resonator and enhanced the temperature stability with TCF = −22 ppm/°C up to 135 °C in comparison to that of TCF = −45 ppm/°C within a temperature range of 25-115 °C of the ZnO/Si structure.     

腐蚀法制备绒面ZnO透明导电薄膜

利用中频脉冲磁控溅射系统制备高透过率、高电导率的平面ZnO薄膜。对平面ZnO薄膜进行短时间弱酸腐蚀,可以获得绒面效果的ZnO透明导电薄膜。分析了工作气压和衬底温度对薄膜绒面结构的影响,获得了适合薄膜太阳能电池的绒面ZnO透明导电薄膜。当压力控制在1.92Pa左右,衬底温度150～170℃范围内沉积的薄膜具有最佳的绒面和较低的电阻率,电阻率可达5.57×10-4Ω·cm,载流子浓度2.2×1020cm-3,霍尔迁移率40.1cm2/V·s,在可见光范围平均透过率超过85%。     

Effects of substrate temperature on electrical and structural properties of copper thin films

This paper addresses the effects of substrate temperature on electrical and structural properties of dc magnetron sputter-deposited copper (Cu) thin films on p-type silicon. Copper films of 80 and 500 nm were deposited from Cu target in argon ambient gas pressure of 3.6 mTorr at different substrate temperatures ranging from room temperature to 250 °C. The electrical and structural properties of the Cu films were investigated by four-point probe and atomic force microscopy. Results from our experiment show that the increase in substrate temperature generally promotes the grain growth of the Cu films of both thicknesses. The RMS roughness as well as the lateral feature size increase with the substrate temperature, which is associated with the increase in the grain size. On the other hand, the resistivity for 80 nm Cu film decreases to less than 5 μΩ-cm at the substrate temperature of 100 °C, and further increase in the substrate temperature has not significantly decreased the film resistivity. For the 500 nm Cu films, the increase in the grain size with the substrate temperature does not conform to the film resistivity for these Cu films, which show no significant change over the substrate temperature range. Possible mechanisms of substrate-temperature-dependent microstructure formation of these Cu films are discussed in this paper, which explain the interrelationship of grain growth and film resistivity with elevated substrate temperature.     

氮气退火对NiO/ZnO:Al薄膜PN结的影响

利用磁控溅射法,在ITO玻璃基底上沉积NiO薄膜和ZnO:Al(Al掺杂的ZnO或AZO)薄膜,制备具有半导体特性的NiO/ZnO:Al透明异质结二极管。使用UV-1700型分光光度计、KEITHLEY4200-SCS半导体测试仪、JSM-6490LV型扫描电子显微镜等分析氮气退火对NiO/ZnO:Al薄膜性能的影响。实验结果表明:500℃退火范围内,NiO薄膜的透过率随退火温度的升高单调上升,500℃时透过率在80%以上,NiO/ZnO:Al薄膜的透过率明显提高;在400℃时,NiO/ZnO:Al薄膜整流特性最佳。     

Ag层的厚度对ZnO/Ag/ZnO多层膜性能的影响

采用射频磁控溅射ZnO陶瓷靶、直流磁控溅射Ag靶的方法制备了不同厚度Ag夹层的ZnO(60nm)/Ag/ZnO(60nm)多层膜.分别用X射线衍射仪、紫外可见分光光度计、四探针测试仪对样品的结构、光学性质、电学性质进行了研究.结果表明:随着Ag层厚度的增加,ZnO/Ag/ZnO多层膜呈现多晶结构,Ag(111)衍射峰的强度增强.Ag夹层厚度为11nm时,ZnO(60nm)/Ag/ZnO(60nm)膜在554nm处的透过率高达92.3%.随着Ag层厚度的增加,Ag膜的特征吸收峰呈现红移和宽化,ZnO/Ag/ZnO多层膜的面电阻先减小后趋于稳定.     

Fabrication and characterisation of high quality ZnO thin films by reactive electron beam evaporation technique

High quality zinc oxide thin films have been deposited on silicon substrates by reactive e-beam evaporation in an oxygen environment. The effect of the growth temperature and air annealing on the structural, optical and electrical properties has been investigated. X-ray diffraction measurements have shown that ZnO films are highly c-axis-oriented and that the linewidth of the (002) peak is sensitive to the variation of substrate temperature. The optimum growth temperature has been observed at 300 °C. Raman spectroscopy has been found to be an efficient tool to evaluate the residual stress in the as-grown ZnO films from the position of the E₂ (high) mode. On the other hand, the vanishing of the 574 cm⁻¹. Raman feature after annealing has been explained as due to an increase of grain size and the reduction of O-vacancy and Zn interstitial. The SEM images have shown that the surfaces of the electron beam evaporated ZnO became smoother for the growth temperatures higher than 300 °C. The optical transmittance is the highest at 300 °C and has been increased after annealing in air showing an improvement of the optical quality. Finally, the maximum electrical resistivity has been found at 300 °C, which explains its relation with the crystal quality and increased from 5.8×10⁻² Ω cm to reach an approximate value of 10⁹ Ω cm after annealing at 750 °C.     

Improved properties of Al-doped ZnO film by electron beam evaporation technique

High-quality Al-doped ZnO (AZO) thin films have been fabricated by electron beam evaporation technique. The effect of the growth temperature on the optical and electrical properties of the electron-beam (e-beam) evaporated AZO film is investigated. X-ray diffraction measurements have shown that e-beam evaporated films are highly c-axis oriented at appropriate growth temperature. Transmittance measurement showed that the best optical and structural quality of the e-beam evaporated AZO film occurred at 200 °C. The scanning electron microscope images have shown that the surfaces of the e-beam evaporated AZO became smoother for the growth temperature at and above 200 °C. Finally, the maximum electrical resistivity of 2.5×10⁻⁴ Ω cm and optical transmittance of more than 85% has been found at 200 °C growth temperature, which explains its relation with the crystal quality of the film.     

Effects of deposition pressure on the properties of transparent conductive ZnO:Ga films prepared by DC reactive magnetron sputtering

Gallium (Ga)-doped zinc oxide (ZnO:Ga) transparent conductive films were deposited on glass substrates by DC reactive magnetron sputtering. Effects of deposition pressure on the structural, electrical and optical properties of ZnO:Ga films were investigated. X-ray diffraction (XRD) studies show that the films are highly oriented with their crystallographic c-axis perpendicular to the substrate almost independent of the deposition pressure. The morphology of the film is sensitive to the deposition pressure. The transmittance of the ZnO:Ga thin films is over 90% in the visible range and the lowest resistivity of ZnO:Ga films is 4.48×10⁻⁴ Ω cm.     

Studies on the properties of sputter-deposited Ag-doped ZnO films

Ag-doped ZnO films were prepared by simultaneous rf magnetron sputtering of ZnO and dc magnetron sputtering of Ag on glass substrate. The influences of dopant content and substrate temperature on the properties of the as-grown films were investigated. Several analytical tools such as X-ray diffraction, spectrophotometer, atomic force microscopy, scanning electron microscopy and four-point probe were used to explore the possible changes in electrical and optical properties. The as-grown film has a preferred orientation in the (0 0 2) direction. As the amounts of the Ag dopant were increased, the crystallinity as well as the transmittance and optical band gap were decreased while the electrical resistivity increased. However, as the substrate temperature was increased, the crystallinity and the transmittance were increased. A small amount of Ag (<1 at%) lowered the resistivity by 30% with only a slight decrease in the visible transparency.     

Low resistive transparent and flexible ZnO/Ag/ZnO/Ag/WO3 electrode for organic light-emitting diodes

Transparent electrodes cannot easily be created with high transmittance and low sheet resistance simultaneously, although some optoelectronic devices, such as large organic light-emitting diode (OLED) displays and lightings, require very low resistive transparent electrodes. Here, we propose a very low resistive transparent electrode (～1.6 Ω/sq) with a high transmittance (～75%) for OLED devices, the transmittance level of which represents the highest reported value to date given such a low sheet resistance level. It consists of a stacked silver (Ag)/zinc oxide (ZnO)/Ag multilayer covered by high refractive index dielectric layers. The proposed multilayer electrode with optimal layer thicknesses has a high and wide spectral transmittance peak due to interference. The low sheet resistance is a result of two Ag layers connected via the sandwiched ZnO layer. In addition to its low sheet resistance coupled with high transmittance, the proposed multilayer electrode has good flexibility. An OLED with an anode of the stacked Ag/ZnO/Ag multilayer shows performance comparable to that of an anode of indium tin oxide.     

Study on the thermal stability of Ga-doped ZnO thin film: A transparent conductive layer for dye-sensitized TiO2 nanoparticles based solar cells

Generally, optoelectronic devices are fabricated at a high temperature. So the stability of properties for transparent conductive oxide (TCO) films at such a high temperature must be excellent. In the paper, we investigated the thermal stability of Ga-doped ZnO (GZO) transparent conductive films which were heated in air at a high temperature up to 500 °C for 30 min. After heating in air at 500 °C for 30 min, the lowest sheet resistance value for the GZO film grown at 300 °C increased from 5.5 Ω/sq to 8.3 Ω/sq, which is lower than 10 Ω/sq. The average transmittance in the visible light of all the GZO films is over 90%, and the highest transmittance is as high as 96%, which is not influenced by heating. However, the transmittance in the near-infrared (NIR) region for the GZO film grown at 350 °C increases significantly after heating. And the grain size of the GZO film grown at 350 °C after annealing at 500 °C for 30 min is the biggest. Then dye-sensitized TiO2 NPs based solar cells were fabricated on the GZO film grown at 350 °C (which exhibits the highest transmittance in NIR region after heating at 500 °C for 30 min) and 300 °C (which exhibits the lowest sheet resistance after heating at 500 °C for 30 min). The dye-sensitized solar cell (DSSC) fabricated on the GZO film grown at 350 °C exhibits superior conversion efficiency. Therefore, transparent conductive glass applying in DSSCs must have a low sheet resistance, a high transmittance in the ultraviolet–visible–infrared region and an excellent surface microstructure.     

衬底温度和溅射偏压对ZnO:Al透明导电膜结构和光电特性的影响

利用射频磁控溅射法在有机薄膜衬底和7059玻璃衬底上制备出了具有良好附着性的低电阻率的 ZnO:Al透明导电膜。研究了薄膜的结构和光电特性与衬底温度的关系,薄膜为多晶纤锌矿结构,垂直于衬底的 c 轴具有[002]方向的择优取向,薄膜的最低电阻率分别为 1.01×10–3ù·cm 和 8.48×10–4ù·cm,在可见光区的平均透过率分别达到了72%和 85%。并研究了溅射偏压对有机衬底 ZnO:Al 薄膜结构及光电特性影响,最佳负偏压为 60 V。     

ITO薄膜的电阻并联效应研究

采用电子束蒸发镀膜方法在K9玻璃基底上分别镀制了ITO/SiO₂/ITO,ITO/Ti₂O₃/ITO和ITO/MgF₂/ITO结构的多层薄膜,用四探针方块电阻仪测量薄膜表面的方块电阻,用原子力显微镜观测样品的表面微观形貌。结果显示,当ITO薄膜的粗糙度较大且介质薄膜的物理厚度小于100nm时,各层ITO薄膜之间通过山峰状的凸起结构相连通,导致样片表面的方块电阻测量值与各层ITO薄膜电阻的并联值相当。这表明,当ITO薄膜的粗糙度较大且介质薄膜厚度较小时,各层ITO薄膜表现出电阻并联效应。利用多层ITO薄膜的电阻并联效应设计并制备了450～1200nm超宽光谱透明导电薄膜,用四探针方块电阻仪测量了试验样片的表面方块电阻,用紫外-可见-近红外分光光度计测试了样片的光谱透射率。结果显示,在相同表面方块电阻条件下,相比于单层ITO薄膜,利用ITO薄膜电阻并联效应所制备的多层透明导电薄膜具有更高的光谱透射率。     

衬底温度对ZnO薄膜氧缺陷的影响

采用射频磁控溅射在石英玻璃和单晶硅Si(100)衬底上制备了ZnO薄膜，研究了衬底温度对ZnO薄膜中氧缺陷的影响。实验发现，ZnO薄膜c轴取向性随温度的升高而增强；当衬底温度达到550。C时，XRD谱上仅出现一个强的(002)衍射峰和一个弱的(004)衍射峰，显示ZnO具有优异c轴取向性。同时，随着温度的升高，ZnO薄膜的紫外透射截止边带向高波长方向漂移，其电导率也随衬底温度的升高逐渐增大，表明薄膜中的氧缺陷逐渐增多。这种氧缺陷是由于ZnO的氧平衡分压高于Zn所致，可通过提高溅射气体中氧含量来改善。     

Inorganic/organic multilayer passivation incorporating alternating stacks of organic/inorganic multilayers for long-term air-stable organic light-emitting diodes

Inorganic/organic multilayer passivation films were fabricated in an effort to enhance the long-term air stability of an organic light-emitting diode (OLED). AlO_x was used as an inorganic layer and 6.5 pairs of alternating silicon monoxide (SiO) and poly zinc acrylate (pZA) layers were used as the organic layers. The organic layers (Alternate stack of SiO and pZA layers) made it possible to decouple the defects present in the inorganic layer (AlO_x) and to increase the penetration length of water and oxygen into the devices. The resulting film was characterized using transmission electron microscopy. The film displayed a high transmittance (>95%) and a low water vapor transmission rate (WVTR, 7.98 × 10⁻⁵ g/m² day) under accelerated environmental aging conditions (a temperature of 60 °C and a relative humidity (R.H.) of 90%). In addition, The OLEDs did not incur significant damage caused by temperature (100 °C) and plasma (100 W) during fabrication process by depositing of SiO onto the OLED device prior to applying the passivation layers. The passivated OLED displayed a prolonged shelf-lifetimes over a period of 3000 h at 60 °C and 90% R.H.