溅射功率对磁控溅射ZnO∶Al(ZAO)薄膜性能的影响

采用射频磁控溅射工艺,以高密度氧化锌铝陶瓷靶为靶材,衬底温度控制在室温,在玻璃基底上制备了透明导电Zn O∶Al(ZAO)薄膜。利用X射线衍射仪(XRD)、原子力显微镜(AFM)、紫外-可见光谱仪和范德堡法,系统研究了不同溅射功率对薄膜的结构、形貌及光电特性的影响。结果表明,不同溅射功率对薄膜的光透射率影响不大,而对薄膜结晶和电学性能影响较大。XRD表明薄膜为良好的c轴择优取向;可见光区(400~600 nm)平均透过率达到85%以上;在120W下沉积的薄膜电学性能达到了最佳。     

衬底温度对磁控溅射法制备ZnO薄膜结构及光学特性的影响

采用射频反应磁控溅射法在玻璃衬底上制备了具有c轴高择优取向的ZnO薄膜,利用X射线衍射仪、扫描探针显微镜及紫外分光光度计研究了生长温度对ZnO薄膜的结构及光学吸收和透射特性的影响.结果表明,合适的衬底温度有利于提高ZnO薄膜的结晶质量;薄膜在紫外区显示出较强的光吸收,在可见光区的平均透过率达到90%以上,且随着衬底温度的升高,薄膜的光学带隙减小、吸收边红移.采用量子限域模型对薄膜的光学带隙作了相应的理论计算,计算结果与实验值符合得较好.     

Influence of annealing temperature on the properties of ZnO:Zr films deposited by direct current magnetron sputtering

Transparent conducting zirconium-doped zinc oxide (ZnO:Zr) films were deposited on quartz substrates by direct current (DC) magnetron sputtering at room temperature. The influence of post-annealing temperature on the structural, morphological, electrical and optical properties of ZnO:Zr films were investigated. When annealing temperature increases from room temperature to 573 K, the resistivity decreases obviously due to an improvement of the crystallinity. However, with further increase in annealing temperature, the crystallinity deteriorates leading to an increase in resistivity. The films annealed at the optimum annealing temperature of 573 K in vacuum have the lowest resistivity of 9.8 × 10⁻⁴ Ω cm and a high transmittance of above 92% in the visible range.     

Influence of substrate temperature on N-doped ZnO films deposited by RF magnetron sputtering

Nitrogen-doped ZnO films were deposited by RF magnetron sputtering in 75% of N₂ / (Ar + N₂) gas atmosphere. The influence of substrate temperature ranging from room temperature (RT) to 300 °C was analyzed by X-ray diffractometry (XRD), spectrophotometry, X-ray photoelectron spectroscopy (XPS), secondary-ion mass spectrometry (SIMS) and Hall measurements setup. The XRD studies confirmed the hexagonal ZnO structure and showed that the crystallinity of these films increased with increasing substrate temperature (T_s). The optical studies indicate the average visible transmittance in the wavelength ranging 500-800 nm increases with increasing T_s. A minimum transmittance (9.84%) obtained for the films deposited at RT increased with increasing T_s to a maximum of 88.59% at 300 °C (500-800 nm). Furthermore, it was understood that the band gap widens with increasing T_s from 1.99 eV (RT) to 3.30 eV (250 °C). Compositional analyses (XPS and SIMS) confirmed the nitrogen (N) incorporation into the ZnO films and its decreasing concentration with increasing T_s. The negative sign of Hall coefficients confirmed the n-type conducting.     

Substrate temperature dependence of the properties of Ga-doped ZnO films deposited by DC reactive magnetron sputtering

Ga-doped zinc oxide (ZnO:Ga) transparent conductive films were deposited on glass substrates by DC reactive magnetron sputtering. The influence of substrate temperature on the structural, electrical, and optical properties of ZnO:Ga films was investigated. The X-ray diffraction (XRD) studies show that higher temperature helps to promote Ga substitution more easily. The film deposited at 350 °C has the optimal crystal quality. The morphology of the films is strongly related to the substrate temperature. The film deposited is dense and flat with a columnar structure in the cross-section morphology. The transmittance of the ZnO:Ga thin films is over 90%. The lowest resistivity of the ZnO:Ga film is 4.48×10⁻⁴ Ω cm, for a film which was deposited at the substrate temperature of 300 °C.     

The properties of Al doped ZnO thin films deposited on various substrate materials by RF magnetron sputtering

Transparent conductive Al-doped ZnO (AZO) thin films were deposited on various substrates including glass, polyimide film (PI) and stainless steel, using radio frequency magnetron sputtering method. The structural, electrical and optical properties of AZO thin films grown on various substrates were systematically investigated. We observe that substrate materials play important roles in film crystallization and resistivity but little on optical transmittance. X-ray diffractometer study shows that all obtained AZO thin films have wurtzite phase with highly c-axis preferred orientation, and films on glass present the strongest (002) diffraction peaks. The presence of compression stress plays critical role in determining the crystalline structure of AZO films, which tends to stretch the lattice constant c and enlarge the (002) diffraction angle. Although the films on the glass present the finest electrical properties and the resistivity reaches 12.52 × 10-4 Ωm, AFM study manifests that films on flexible substrates, especially stainless steel, bestrew similar inverted pyramid structure which are suitable for window material and electrode of solar cells. The average optical transmittance of AZO thin films deposited on glass and PI are both around 85% in the visible light range (400–800 nm).     

Transparent conductive ZnO:B films deposited by magnetron sputtering

This paper focuses on the preparation of boron doped ZnO (ZnO:B) films prepared by nonreactive mid-frequency magnetron sputtering from ceramic target with 2 wt.% doping source. Adjusting power density, ZnO:B film with low resistivity (1.54 × 10^− 3 Ω cm) and high transparency (average transparency from 400 to 1100 nm over 85%) was obtained. Different deposition conditions were introduced as substrate fixed in the target center and hydrogen mediation. Hall mobility increased from 11 to above 26 cm²/V·s, while carrier concentration maintained almost the same, leading to low resistivity of 6.45 × 10^− 4 Ω cm. Transmission spectra of ZnO:B films grown at various growth conditions were determined using a UV-visible-NIR spectrophotometer. An obvious blue-shift of absorption edge was obtained while transmittances between 600 nm and 1100 nm remained almost the same. Optical band baps extracted from transmission spectra showed irregular enhancement due to the Burstein-Moss effect and band gap renormalization. Photoluminescence spectra also showed a gradual increase at UV emission peak due to free exciton transition near band gap. We contributed this enhancement in both optical band gap and UV photoluminescence emission to the lattice structure quality melioration.     

Effect of substrate temperature on the structure and optical properties of ZnO thin films deposited by reactive rf magnetron sputtering

Zinc Oxide films were deposited on quartz substrates by reactive rf magnetron sputtering of zinc target. The effect of substrate temperature on the crystallinity and band edge luminescence has been studied. The films deposited at 300 °C exhibited the strongest c-axis orientation. AFM and Raman studies indicated that the films deposited at 600 °C possess better overall crystallinity with reduction of optically active defects, leading to strong and narrow PL emission.     

Room temperature deposition and properties of ZnO:Al thin films by nonreactive DC magnetron sputtering

Transparent and conductive ZnO:Al (AZO) thin films were prepared at room temperature by nonreactive DC magnetron sputtering from ceramic ZnO:Al targets. The effects of Al doping level and argon gas pressure on microstructure, growth behavior, resistivity and transmittance of AZO thin films were investigated. The experimental results show that AZO thin films change from polycrystalline to preferred c-axis-orientation just at high argon gas pressure. The resistivity of AZO films first decreases with the increase of Al content under 3 wt%, then increases when the Al content is over 3 wt%. The argon gas pressure also effect on the resistivity of AZO thin films due to the change of dispersion related the grain and crystal boundary. When the argon gas pressure from 0.6 to 3.0 Pa, the resistivity of AZO films decreases to a lowest resistivity of 1.4 × 10⁻³ Ω cm when the argon gas pressure is 1.5 Pa, then increases gently. The Al content and argon gas pressure had a little influence on transmittance, and the average optical transmittances of AZO thin films were from 86% to 90%, but the absorption edge has a blue shift with the increase of doping level and argon gas pressure.     

Preparation and properties of surface textured ZnO: Al films by direct current pulse magnetron sputtering

Transparent conductive surface textured Al-doped zinc oxide (ZnO:Al, AZO) thin films were prepared on glass substrates by direct current pulse magnetron sputtering at substrate temperature of 270 °C and post-etching in NaOH solution at room temperature. The effects of Ar flow rate on the structural, optical, electrical properties and light trapping ability were investigated systematically. With the increasing of Ar flow rate from 10 to 50 sccm, different surface features ranging from honeycomb-like to crater-like structures were observed. The relationship between surface textured structures and Ar flow rate was discussed. The AZO film deposited with Ar flow rate in 50 sccm displayed fine optoelectronic properties, improved figure of merit and effective surface textured structures for light trapping, which could be applied as a transparent conducting electrode in silicon-based thin film solar cells.     

Effect of target properties on transparent conducting impurity-doped ZnO thin films deposited by DC magnetron sputtering

For the purpose of using transparent conducting impurity-doped ZnO thin films in liquid crystal display (LCD) applications, the relationship between the properties of dc magnetron sputtering (dc-MS) deposited thin films and the properties of the oxide targets used to produce them is investigated. Both Al-doped and Ga-doped ZnO (AZO and GZO) thin films were deposited on glass substrates using a dc-MS apparatus with various high-density sintered AZO or GZO disk targets (diameter of about 150 mm); the target and substrate were both fixed during the depositions. Using targets with a lower resistivity results in attaining more highly stable dc-MS depositions with higher deposition rates and lower arcing. In addition, dc-MS depositions using targets with a lower resistivity produced improvements in resistivity distribution on the substrate surface. It was found that the oxygen content in deposited thin films decreased as the oxygen content of the target used in the deposition was decreased. As a result, the dc-MS deposition of transparent conducting impurity-doped ZnO thin films suitable for LCD applications requires the preparation of significantly reduced AZO and GZO targets with low oxygen content.     

倾斜磁控溅射低温沉积ZnO∶Al薄膜及其光电性能的研究

利用直流-射频共溅射法在玻璃基底上低温制备了系列掺铝氧化锌(ZAO)透明导电薄膜。研究了低温溅射过程中倾斜溅射靶偏角对样品电学性能、紫外-可见-近红外光区透过率、X射线衍射谱及薄膜表面形貌的影响。结果表明,室温条件下制备的ZAO薄膜具有(002)择优取向,当靶偏角为23°时,薄膜方块电阻最低,可达17Ω/□,电阻率为2.2×10-3Ω·cm,可见光平均透过率在85%以上,最高可在95%以上。紫外截止和近红外反射效果明显。     

ZnO:Al thin films deposited by RF-magnetron sputtering with tunable and uniform properties

Nanostructured, high quality and large area Al-doped ZnO (ZnO:Al) thin films were obtained by radiofrequency (RF) magnetron sputtering. The sample rotation during deposition has resulted in excellent spatial distribution of thickness and electro-optical properties compared to that obtained under static conditions. ZnO:Al thin films are employed in a large number of devices, including thin film solar cells, where the uniformity of the properties is a key factor for a possible up-scaling of the research results to industrially relevant substrate sizes. A chemical post etching treatment was employed achieving tunable surface nanotextures to generate light scattering at the desired wavelength for improved cell efficiency. Since the film resistivity is only slightly increased by the etching, this post-deposition step allows separating the optimization of electro-optical properties from light scattering behavior. The thin films were characterized by FE-SEM, XRD, UV-VIS spectroscopy, four probe and van der Paw techniques.     

Mn-doped ZnO transparent conducting films deposited by DC magnetron sputtering

Mn-doped zinc oxide (ZnO:Mn) thin films with low resistivity and relatively high transparency were firstly prepared on glass substrate by direct current (DC) magnetron sputtering at room temperature. Influence of film thickness on the properties of ZnO:Mn films was investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that all the deposited films are polycrystalline with a hexagonal structure and have a preferred orientation along the c-axis perpendicular to the substrate. As the thickness increases from 144 to 479 nm, the crystallite size increases while the electrical resistivity decreases. However, as the thickness increases from 479 to 783 nm, the crystallite size decreases and the electrical resistivity increases. When film thickness is 479 nm, the deposited films have the lowest resistivity of 2.1 × 10^− 4 Ω cm and a relatively high transmittance of above 84% in the visible range.     

衬底温度对低功率直流磁控溅射ZnO薄膜特性的影响

采用低功率直流反应磁控溅射法,在Si衬底上成功制备出了具有高c轴择优取向的ZnO薄膜,利用X射线衍射仪、荧光分光光度计研究了沉积温度对ZnO薄膜微观结构及光致发光特性的影响.结果表明,合适的衬底温度有利于提高ZnO薄膜结晶质量;在室温下测量样品的光致发光谱(PL),观察到波长位于440nm左右和485nm左右的蓝色发光峰及527nm左右微弱的绿光峰,随衬底温度升高,样品的PL谱中蓝光强度都明显增大,低功率溅射对其蓝光发射具有很重要的影响.综合分析得出440nm左右的蓝光发射应与Zni有关,485nm附近的蓝光发射是由于氧空位形成的深施主能级上电子跃迁到价带顶的结果,而527nm左右的较弱的绿光发射主要来源于导带底到氧错位缺陷能级的跃迁.生长温度主要是通过改变薄膜中缺陷种类及浓度而影响着ZnO薄膜的发光特性的.     

Electrical and optical properties of ZnO:Al thin films grown by magnetron sputtering

The properties of transparent conductive ZnO:Al thin films grown by R.F. magnetron sputtering method are investigated. The working pressure (argon gas) is changed from 2.5 to 40.0 mTorr to study its influence on the characteristics of ZnO:Al thin films. The ZnO:Al thin films have better texture due to the increase in the surface mobility, which resulted from the increase in the mean free path of sputtering gas under lower working pressure. The microstructure of ZnO:Al films is found to be affected obviously by changing the working pressure. It is shown that the grain size of ZnO:Al thin films decreases with the increase of working pressure. The X-ray diffraction patterns indicate that the poor crystallized structure of ZnO:Al films is obtained at higher working pressure. Except 40 mTorr, the highly (002)-oriented ZnO:Al thin films can be found at the measured range of working pressure. Moreover, the growth rate of the films decreases from 1.5 to 0.5 nm/min as the working pressure increases from 2.5 to 40.0 mTorr. The results of optical transmittance measurement of ZnO:Al thin films reveal a high transmittance (>80%) in visible region and exhibit a sharp absorption edge at wavelength about 350 nm.     

溅射电流对磁控溅射CrN_x薄膜结构与性能的影响

采用非平衡磁控溅射技术在不锈钢以及单晶硅基体上制备了CrNx薄膜,并利用X射线衍射仪(XRD)、场发射扫描电镜(FESEM)、能量色散X射线能谱仪(EDS)和纳米压痕仪对薄膜的结构和性能进行了表征。结果表明,随着溅射电流的增大,薄膜中N/Cr比值减小,相组成由CrN(200)向Cr2N(111)转变;晶粒尺寸减小,柱状结构消失,结构变得致密;由于在大溅射电流下,易于形成Cr2N高硬度相,而且形成的薄膜晶粒细小、结构致密,所以硬度值随溅射电流单调升高,在21A时达到最高,为21GPa。     

利用脉冲直流磁控溅射制备ZnO:Al薄膜的研究

利用中频脉冲直流磁控溅射法制备了平面ZnO:Al(AZO)透明导电薄膜,研究了沉积压力、衬底温度和溅射功率对AZO薄膜光电性能、薄膜稳定性的影响.结果表明:在较低沉积压力、衬底温度及溅射功率下,可获得具有低电阻率、高透过率、高稳定性的AZO薄膜.     

Structural characterization of ZnO thin films deposited by dc magnetron sputtering

In this work we present recent results on ZnO thin films grown by dc magnetron sputtering technique at room temperature (RT), focusing on structural and surface characterization using conventional cross-section transmission electron microscopy (XTEM) and high resolution cross section transmission electron microscopy (HRXTEM) in an attempt to understand the thickness influence on film, mechanical and optical properties as well as photoreduction/oxidation conductivity changes. Films were found to be polycrystalline with a columnar mode of growth. For films with thickness over 100 nm, XTEM and HRTEM analysis evidenced the presence of a small grains transition layer near interface with the substrate, feature which plays an important role in ZnO thin films for gas sensing application. The control of such structural parameters is proved to be critical for the improvement of their gas sensing performance.     

Preparation and character of textured ZnO:Al thin films deposited on flexible substrates by RF magnetron sputtering

ZnO:Al thin films deposited on transparent TPT substrates by magnetron sputtering were etched in acetic acid solution. The effects of etching solution concentration and etching time on the structure and properties of ZnO:Al films were investigated. The obtained films had a hexagonal structure and a highly preferred orientation with the c-axis perpendicular to the substrate. The ZAO film etched in 1% acetic acid solution for 10 s had a pyramidal structure and an enhanced light scattering ability, the average transmittance and reflectance in the visible region were 72% and 26% respectively, the sheet resistance was 260 Ω/□. Both transmittance and reflectance of the films decreased as the etching solution concentration and etching time increasing. Etching had a negative effect on the conductive properties of ZAO films. The lowest sheet resistance was 120 Ω/□ for the ZAO film without etching.