Improved ITO thin films with a thin ZnO buffer layer by sputtering

In this paper, we report a buffering method of improving the quality of ITO thin films on glass by r.f. magnetron sputtering. By applying a ZnO buffer before the ITO deposition in the same run of sputtering, ITO films showed single (111)-oriented highly textured structure, while ITO films showed mixed-oriented polycrystalline structure on bare glass. A design of experiment was taken out to minimize the resistivity of ITO films in the deposition parameter space (oxygen ratio, total gas pressure, and temperature). Resistance measurements showed that the ITO films with ZnO buffers had a remarkable 50% decrease of resistivity comparing to those without ZnO buffers at optimized deposition condition. Room-temperature Hall effect measurements showed that the decrease in resistivity comes from a large increase of mobility and a slight increase of carrier density after forming gas annealing. The ZnO/glass may be a good alternative substrate to bare glass for producing high quality ITO films for advanced electro-optic applications.     

原子层沉积低温制备AZO薄膜

采用原子层沉积技术与改进的Al掺杂模式在石英玻璃基体上低温制备AZO薄膜,利用椭圆偏振仪、原子力显微镜、X射线衍射仪、X射线光电子能谱仪、Hall效应测试仪系统地对样品的生长速率、表面形貌、晶体结构、薄膜成分与电学性能进行了表征和分析。结果表明,采用原子层沉积在150℃下制备AZO薄膜,其为六方纤锌矿结构,Al掺杂对Zn O的(002)有明显的抑制作用,Al在基体中弥散分布,其部分替换Zn O晶格中的Zn,以Al—O的形式存在于晶体中,晶体中存在大量的氧空位,最佳铝锌循环比为1∶19,此条件下AZO薄膜电阻率为4.61×10-4Ω·cm。     

ZnO缓冲层上低温生长Al掺杂的ZnO薄膜

采用射频磁控溅射法在ZnO缓冲层上制备了不同Al掺杂量的ZnO（AZO）薄膜。利用X射线衍射（XRD）、扫描电子显微镜（SEM）和光致发光（PL）等表征技术,研究了AZO薄膜的微观结构、表面形貌和发光特性。结果表明,随着Al掺杂量的增加,ZnO薄膜的择优取向性发生了改变,且当Al的掺杂量为0.81%（原子分数）时,（002）衍射峰与其它衍射峰强度的比值达到最大,表明适合的Al掺杂使ZnO薄膜的择优取向性得到了改善。在可见光范围内薄膜的平均透过率超过70%。通过对样品光致发光（PL）谱的研究,发现所有样品出现了3个发光峰,分别对应于以444nm（2.80eV）、483nm（2.57eV）为中心的蓝光发光峰和以521nm（2.38eV）为中心较弱的绿光峰。并对样品的发光机理进行了详细的探讨。     

Carbon nitride as a buffer layer for magnetic thin films

Amorphous carbon nitride (CN_{x, 0.1<x<0.3}) thin films present a unique combination of hardness and compliance and may be useful for incorporation into ferromagnetic multilayers. We present a study of the use of amorphous CN_x as a buffer layer for NiFe magnetic thin films. The surface roughness of the NiFe films is comparable to films on Ta or Cu buffer layers and is stable with annealing at 200 °C. Effects on the magnetization and coercivity are seen, and may be due to several mechanisms, including chemical reactions at the interface and interdiffusion.     

Electron-beam irradiation induced optical transmittance enhancement for Au/ITO and ITO/Au/ITO multilayer thin films

Electron beam(EB) irradiation experiments on Au/ITO and ITO/Au/ITO multilayer thin films are reported.The structure and the optical-electrical properties of the samples were investigated by X-ray diffraction,atomic force microscopy, four-point probe resistivity measurement system, and UV–vis-NIR double beam spectrometer, respectively. Those results show that the EB irradiation has the effects of improving the crystalline of samples, widening the optical band gap of both thin films, reducing the sheet resistance,and improving the transmittance of samples.     

Effects of sputtering pressure and Al buffer layer thickness on properties of AZO films grown by rf magnetron sputtering

Transparent and conductive Al-doped (2 wt.%) zinc oxide (AZO) films were deposited on inexpensive soda-lime glass substrates by using rf magnetron sputtering at room temperature. This study analyzed the effects of argon sputtering pressure, which varied in the range from 0.46 to 2.0 Pa, on the morphological, electrical and optical properties of AZO films. The only (0 0 2) diffraction peak of the film were observed at 2θ～34.45°, exhibiting that the AZO films had hexagonal ZnO wurtzite structure, and a preferred orientation with the c-axis perpendicular to the substrate. By applying a very thin aluminum buffer layer with the thickness of 2 nm, findings show that the electrical resistivity was 9.46 × 10⁻⁴ Ω-cm, and the average optical transmittance in the visible part of the spectra was approximately 81%. Furthermore, as for 10 nm thick buffer layer, the electrical resistivity was lower, but the transmittance was decreased.     

ITO thin films prepared by a microwave heating

ITO thin films were prepared by irradiating 2.45 GHz of microwave with an output power of 700 W using a commercial kitchen microwave oven. A substrate temperature went up and down rapidly between 100 and 650 °C in a minute by a dielectric loss of SnO₂ layer pre-deposited on a glass substrate. We found that the electrical and optical properties of films were affected by the atmosphere in a microwave irradiation, while the sintering was completed within a few minutes. Although the electrical resistivity was not reduced below 5.0 × 10^− 4 Ω·cm in this study, the results lead to the possibility of a practical rapid synthesis of ITO transparent conducting oxide films.     

直流磁控溅射制备大面积AZO透明导电薄膜

采用直流磁控溅射工艺于200℃的玻璃基板制备了大面积AZO透明导电薄膜。重点研究了样品晶体结构、方阻、可见光透过率、样品形貌等随其位置变化的情况。研究表明,大面积AZO薄膜的晶体结构、可见光透过率、样品形貌等随样品位置变化比较小,大面积AZO样品均按C轴取向生长,表面平整,晶粒尺寸为20 nm左右。在本实验条件下获得的大面积AZO薄膜方阻在86～110Ω/□范围内,方阻线性变动率为28%,样品电阻率为6.34～7.26×10-4Ω·cm,可见光平均透过率均高于87%。     

Suppression of phase transitions in Pd thin films by insertion of a Ti buffer layer

We investigated the effects of a thin titanium (Ti) buffer layer on structural changes and electrical responses of palladium (Pd) thin films. A Ti buffer layer was inserted between a Pd film and the substrate, with varying thickness from 0.5 to 80 nm. Unlike pure Pd films, Ti-buffered Pd films showed no structural deformations after cyclic exposure to hydrogen gas, leading to a linear relationship between sensitivity and hydrogen gas concentration over the measured concentration range of 0 to 2%. This was attributed to the suppression of phase transitions from the α to the β phase in Pd films, due to the reinforced film adhesion by the inserted Ti layer. Our results highlight the practical usability of Pd thin films as reliable and sensible hydrogen sensors, enabled simply by the insertion of a thin Ti buffer layer.     

Optical properties of PZT thin films deposited on a ZnO buffer layer

The optical properties of lead zirconate titanate (PZT) thin films deposited on ZnO were studied by m-lines spectroscopy. In order to retrieve the refractive index and the thickness of both layers from the m-lines spectra, we develop a numerical algorithm for the case of a two-layer system and show its robustness in the presence of noise. The sensitivity of the algorithm of the two-layer model allows us to relate the observed changes in the PZT refractive index to the PZT structural change due to the ZnO interface of the PZT/ZnO optical waveguide.     

离子束辅助磁控溅射低温沉积ITO透明导电薄膜的研究

本文对离子束辅助磁控溅射低温沉积的ITO薄膜进行了研究,重点考察了辅助离子束能量对ITO薄膜的光电性能和晶体结构的影响。结果表明:当A r/O2辅助离子束能量为900 eV左右时能够有效改善ITO薄膜的光电性能,在从非晶到多晶的转变过程中ITO薄膜具有较低的电阻率。在聚碳酸酯(PC)基片上制备了平均可见光透过率81.0%、电阻率为5.668×10-4ohm cm、结构致密且附着力良好的ITO薄膜,基片无变形。     

ITO thin films deposited by advanced pulsed laser deposition

Indium tin oxide thin films were deposited by computer assisted advanced PLD method in order to obtain transparent, conductive and homogeneous films on a large area. The films were deposited on glass substrates. We studied the influence of the temperature (room temperature (RT)-180 °C), pressure (1-6 × 10^− 2 Torr), laser fluence (1-4 J/cm²) and wavelength (266-355 nm) on the film properties. The deposition rate, roughness, film structure, optical transmission, electrical conductivity measurements were done. We deposited uniform ITO thin films (thickness 100-600 nm, roughness 5-10 nm) between RT and 180 °C on a large area (5 × 5 cm²). The films have electrical resistivity of 8 × 10^− 4 Ω cm at RT, 5 × 10^− 4 Ω cm at 180 °C and an optical transmission in the visible range, around 89%.     

溶胶-凝胶法制备ITO薄膜研究进展

概述了近年来国内外溶胶-凝胶法(Sol-Gel)制备ITO薄膜的研究状况,对Sol-Gel法制备ITO薄膜工艺做了简要介绍,重点讨论了Sol-Gel法制备ITO薄膜的溶胶体系,分析比较了有机醇盐、无机盐以及掺入ITO粉末方法体系的优缺点,最后讨论了甩膜法、提拉法及平铺法在Sol-Gel法制备ITO薄膜中镀膜的应用.指出Sol-Gel法是一种高效可行的制备ITO薄膜的方法,有着广阔的应用前景.     

Effect of SiO2 buffer layer thickness on the properties of ITO/Cu/ITO multilayer films deposited on polyethylene terephthalate substrates

Transparent conductive ITO/Cu/ITO films were deposited on polyethylene terephthalate (PET) substrates with a SiO₂ buffer layer by magnetron sputtering using three cathodes at room temperature. The effect of the SiO₂ buffer layer thickness on the electrical and optical properties of ITO/Cu/ITO films was investigated. The ITO/Cu/ITO film deposited on the 40 nm thick SiO₂ buffer layer exhibits a sheet resistance of 143Ω/sq and transmittance of 65% at 550 nm wavelength. Highly transparent ITO/Cu/ITO films with a transmittance of 80% and a sheet resistance of 98.7Ω/sq have been obtained by applying −60 V substrate bias.     

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.     

Enhancement of nonlinear optical susceptibility of CuPc films by ITO layer

In the present study, the Copper Phthalocyanine (CuPc)/ITO thin film was fabricated using thermal evaporation method. The structural property was analyzed by X-ray diffraction study and confirms that the thin film has been preferentially grown along (200) plane. The atomic force microscope study was carried out on deposited film and quality of thin films is assessed by calculating the roughness of the films. The direct and indirect band gap, linear and nonlinear optical characteristics of grown films were calculated by using UV–Vis–NIR spectrometer studies. The calculated values of the first direct and indirect band gaps (E_g1(d) & E_g1(ind)) are 1.879 and 1.644 eV as a fundamental gap, while the values of second direct and indirect band gap (E_g2(d) & E_g2(ind)) are 1.660 and 1.498 eV as an onset gap for CuPc. The values of nonlinear refractive index (n₂) and third order nonlinear optical susceptibility (χ³) are found to be 5 × 10⁻⁸ and 8 × 10⁻⁹ (theoretical) and 5.2 × 10⁻⁸ and 1.56 × 10⁻⁷ (experimental) respectively. The optical band and third order nonlinear properties suggest that the as-prepared films are may be applied in optoelectronic and nonlinear applications.     

Optical characteristics of thin ZnSe films of different thicknesses

Polycrystalline ZnSe films of thicknesses 54–785 nm deposited on glass substrates by thermal evaporation were investigated. X-ray diffraction analysis was carried out on as-deposited and annealed films to determine their structure. The ZnSe films were polycrystalline of cubic structure with preferred [111] orientation. Transmission and reflection at normal incidence were performed on ZnSe films in the wavelength range 350–2500 nm to determine the optical constants and optical energy gap. The optical gaps of ZnSe films show remarkable dependence on the film thickness. Analysis of the absorption data revealed the existence of two transition processes (with energy gaps at 2.7 and 2.22 eV for the bulk ZnSe).     

Preparation and electrical properties of ITO thin films by dip-coating process

Indium tin oxide (ITO) thin films were prepared on quartz glass substrates by a dip-coating process. The starting solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol. The ITO thin films containing 0 20 mol% SnO₂ were successfully prepared by heat-treatment at above 400 °C. Chemical stability of sol were investigated by using a FTIR spectrometer. The electrical resistivity of the thin films decreased with increasing heat-treatment temperature, that is carrier concentration increased, and mobility decreased with increasing SnO₂ content. The ITO thin films containing 12 mol% SnO₂ showed the minimum resistivity of =1.2 × 10^–3 ( cm). It also showed high carrier concentration of N=1.2 × 10²⁰(cm^–3) and mobility _H=7.0(cm² V^–1 s^–1).     

室温直流磁控溅射制备ITO膜及光电性能研究

室温条件下,在玻璃衬底上,采用直流磁控溅射法制备了ITO膜.研究了溅射压强,氧流量和溅射功率等工艺参数对薄膜光电性能的影响.结果表明当Ar流量为44.2 sccm和溅射时间20 min等参数不变时,溅射气压0.7 Pa,氧流量0.62 sccm和溅射功率130 W为最佳工艺条件.并得到了电阻率5.02×10-4 Ω·cm,在可见光区平均透过率80%以上ITO薄膜.