Preparation and optical properties of W-doped VO2/AZO bilayer composite film

In order to improve its visible light transmittance, W-doped VO₂ thin film was prepared with direct current (DC) reactive magnetron sputtering on the surface of Al-doped ZnO (AZO) thin film deposited on quartz glass substrate in advance with radio frequency (RF) magnetron sputtering. The effects of sputtering power for AZO film were investigated on the crystal structures, surface morphologies and optical properties of AZO thin film and W-doped VO₂/AZO bilayer composite film. The results show that the crystallinity of both AZO monolayer film and the bilayer film first increases and then decreases with the increase of sputtering power. As the sputtering power increases, the film thickness increases. The integral visible luminous transmittance (T_lum) of the W-doped VO₂/AZO bilayer film decreases continuously, and the solar modulation efficiency (ΔT_sol) increases first and then decreases. When the sputtering power is 150 W, T_lum and ΔT_sol of W-doped VO₂/AZO bilayer film are 30.14% and 11.95%, 2.77% and 1.71% higher than those of W-doped VO₂ monolayer film, respectively.     

Preparation and properties of AZO/PS/AZO tri-layer transparent conductive film with a light-trapping structure

The light-trapping structure is an effective method to increase solar light capture efficiency in the solar cells. In this study, Al-doped ZnO (AZO)/polystyrene (PS)/AZO tri-layer transparent conductive film with light-trapping structure was fabricated by magnetron sputtering and liquid phase methods. The structural, optical and electrical properties of the AZO films could be controlled by different growth conditions. When the sputtering pressure of the under-layer AZO film was 0.2 Pa, the discharge voltage was around 80 V, which was within the optimal process window for obtaining AZO film with high crystallinity. The optimal under-layer AZO film had a large surface roughness and a very low static water contact angle of 75.71°, promoting the relatively uniform distribution of PS spheres. Under this sputtering condition, the prepared AZO/PS/AZO tri-layer film had the highest crystallinity and least point defects. The highest carrier concentration and Hall mobility are 3.0 × 10²¹ cm^-3and 5.39 cm² V^-1 s^-1, respectively. Additionally, a transparent conductive film with the lowest resistivity value (3.88 × 10^-4 Ω cm) and the highest average haze value (26.5%) was obtained by optimizing the process parameters. These properties were comparable to or exceed the reported values of surface-textured SnO₂-based as well as ZnO-based TCOs films, making our films suitable for transparent electrode applications, especially in thin-film solar cells.     

Temperature field and residual stress analysis of multilayer pyroelectric thin film

The two-dimensional finite element model was built for the multilayer pyroelectric thin film. The temperature field and residual stress were simulated. The results show that porous silica film as a thermal-insulation layer and a reasonable model structure are effective for decreasing the heat loss. The silicon substrate and pyroelectric thin film that influence the temperature variation rate in pyroelectric thin film are also discussed. The annealing temperature and model structure have significant influence on residual stresses of pyroelectric thin film. The residual stresses increase rapidly with the increase of annealing temperature. The scanning electron microscopy (SEM) is employed to investigate the morphology of the pyroelectric thin film. The results show that the pyroelectric thin film annealed at 750 °C has a crack structure.     

Effects of film and substrate dimensions on warpage of film insert molded parts

Three‐dimensional flow and structural analyses were carried out for film insert injection molding to investigate warpage of film insert molded (FIM) parts with respect to variation of film and substrate thickness. Asymmetry of temperature distribution in the thickness direction was increased with increasing film thickness but decreased with increasing substrate thickness. Asymmetry of the in‐mold residual stress distribution in the FIM specimen was generated by the nonuniform temperature distribution, and it was increased with increasing film thickness but reduced with increasing substrate thickness. Warpage of the ejected FIM specimen was determined by relaxation of the asymmetric in‐mold residual stress distribution, and it was increased with increasing film thickness but reduced with increasing substrate thickness. Warpage of FIM specimens annealed at 80°C for 30 min showed complex behavior, and the behavior was understood by using factors such as degree of warpage of the ejected part, thermal shrinkage of the inserted film, and retardation of heat transfer. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Effects of inclination angle applied to a polyethylene terephalate substrate before the coating of Al-doped ZnO on film quality and mechanical and optical properties

A flat plate in the deposition stage is designed to be tilted flexibly with an angle such that an inclination angle is formed between the ion beam and the direction normal to a polyethylene terephthalate (PET) substrate. Five kinds of PET/aluminum-doped zinc oxide specimen, with 0°, 15°, 30°, 45°, and 60° inclination angles, respectively, were prepared to examine the effect of inclination angle on the mechanical, electrical, and optical properties and morphology of coating films. Using the peaks of the ZnO (002) and ZnO (103) planes in X-ray diffraction analyses, the relative intensity ratios for these two crystallines are defined and used to evaluate the parameters of composite grain size ((g)_Composite) and residual stress ((σ)_Composite). The experimental results indicate that (σ)_Composite increases but (g)_Composite mostly decreases with increasing inclination angle. A nearly linear relationship is found between (g)_Composite and the d-spacing parameter ((d)_Composite). They both decrease with increasing inclination angle. The intensities of ZnO (002) and ZnO (103) planes significantly influence the mean transmittance, absorption, and reflection in the wavelength range of 801–2500 nm (near-infrared). An increase in the relative peak intensity of ZnO (002) increases the mean transmittance and thus lowers the mean absorption and reflectance. The average transmittance decreases and the average reflection increases in the wavelength range of 300–2500 nm with increasing inclination angle. Increasing the composite grain size decreases the average reflection. The ZnO film thickness is proportional to the mean surface roughness of the film.     

Residual stresses and thermoviscoelastic deformation of laminated film prepared for film insert molding

Residual stresses and thermoviscoelastic deformation of a laminated film utilized for film insert molding was investigated through measurement of thermal expansion coefficient (CTE) and relaxation modulus. Thermoviscoelastic deformation of the film was also analyzed with numerical analysis by applying measured relaxation modulus, CTE, and residual stress to finite element method (FEM). Stress relaxation of the pristine film showed significantly different behavior from that of the unannealed film during annealing. Effects of the CTE and relaxation modulus on the thermoviscoelastic deformation were predicted by considering thermal shrinkage and structural relaxation. Moreover, numerical results on thermoviscoelastic deformation were in good agreement with experiments when initial stress distribution in the solid specimen was applied to the numerical analysis. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Enhancing optical and electrical properties of Al-doped ZnO coated polyethylene terephthalate substrates by laser annealing using overlap rate controlling strategy

Aluminum-doped zinc oxide (AZO) layers were deposited on polyethylene terephthalate (PET) flexible substrates and optimized by laser annealing using a 532 nm nanosecond pulsed laser. Effects of overlap rates, i.e. laser spot overlap rate (SO_R) and laser scan line overlap rate (LO_R), on AZO/PET films were investigated by X-ray diffractometer (XRD), scanning electron microscope (SEM), UV–visible transmittance spectra and digital four-point probe instrument, respectively. Laser annealing could greatly enhance grain crystallinity, increase crystallite size and avoid damage to the PET flexible substrates, thus effectively enhance transmittance and conductivity of the films. The results showed that the AZO/PET film annealed by using 85% SO_R and 60% LO_R presented the highest average visible transmittance of 76.2% and the lowest resistivity of 1.95×10⁻³ Ω cm, which respectively improved by approximately 23% and 75% compared to those of the as-deposited AZO/PET film. This work may be of great importance from the viewpoint of performance optimization of transparent conductive oxide (TCO) flexible films.     

Transparent and high infrared reflection film having sandwich structure of SiO2/Al:ZnO/SiO2

New transparent and high infrared reflection films having the sandwich structure of SiO₂/Al:ZnO(AZO)/SiO₂ were deposited on the soda-lime silicate glass at room temperature by radio frequency (R.F.) magnetron sputtering. The optical and electrical properties of SiO₂ (110 nm)/AZO (860 nm)/SiO₂ (110 nm) sandwich films were compared with those of single layer AZO (860 nm) films and double layer SiO₂ (110 nm)/AZO (860 nm) films. The results show that these sandwich films exhibit high transmittance of over 85% in the visible light range (380–760 nm), and low reflection rate of below 4.5% in the wavelength range of 350–525 nm, which is not shown in the conventional single layer AZO (860 nm) films and double layer SiO₂ (110 nm)/AZO (860 nm) films. Further these sandwich films display a low sheet resistance of 20 Ω/sq by sheet resistance formula and high infrared reflection rate of above 80% in the wavelength range of 15–25 μm. In addition, the infrared reflection property of these sandwich films is determined mainly by the AZO film. The outer SiO₂ film can diminish the interference coloring and increase transparency; the inner SiO₂ film improves the adhesion of the coating to the glass substrate and prevents Ca²⁺ and Na⁺ in the glass substrate from entering the AZO film.     

Molded geometry and viscoelastic behavior of film insert molded parts

Virgin injection‐molded tensile specimens without any inserted film and four kinds of film insert molded (FIM) tensile specimens were prepared. They were annealed at 80°C to investigate the effect of residual stresses and thermal shrinkage of the inserted film on thermal deformation of tensile specimens. The FIM specimens with the unannealed film were bent after ejection in such a way that the film side was protruded and the warpage was reversed gradually during annealing and the film side was intruded. Warpage of the FIM specimen with the film annealed at 80°C for 20 days was not reversed during annealing. Processing of the FIM specimens have been modeled numerically to predict thermoviscoelastic deformation of the part and to understand the warpage reversal phenomenon (WRP). Nonisothermal three‐dimensional flow analysis was carried out for filling, packing, and cooling stages. The flow analysis results were transported to a finite element stress analysis program for prediction of deformation of the FIM part. The WRP was caused by the combined effect of thermal shrinkage of the inserted film and relaxation of residual stresses in the FIM specimen during annealing. It is expected that this study will contribute towards the improvement of the FIM product quality and prevention of large viscoelastic deformation of the molded part. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Rejuvenation and physical ageing of a polycarbonate film subjected to finite tensile strains

Differential storage and loss tensile moduli, E′ and E″, were determined intermittently at 10 Hz on specimens of an annealed polycarbonate film during stress relaxation at static tensile strains from 1.2 to 6.25% at 50°C. It was found that E′ and 1/E″ decrease when a static strain is applied but thereafter they increase progressively with time. These changes, which increase with the applied strain until it becomes 4%, are attributed primarily to a rejuvenation of a specimen (an increase in segmental mobility) followed by physical ageing (a progressive decrease in segmental mobility). Measurements at a static strain of 3% at six temperatures from 30°C to 130°C showed, among other things, that the rates of increase of E′ and decrease of E″ are sensibly independent of temperature up to 110°C.     

Facile synthesis of metal organic decomposition Al-doped ZnO ink for inkjet printing and fabrication of highly transparent conductive film

In this paper, a MOD (Metal organic decomposition) Al doped ZnO (AZO) ink was directly used for inkjet printing transparent and conductive AZO films. The ink was synthesized by using zinc acetate dihydrate and aluminum nitrate nonahydrate as precursor, 1,2-diaminopropane as a complexing agent, ethyl alcohol as solution, ethyl cellulose as addition agent. The thermal decomposition behavior of the MOD ink was investigated. The various MOD AZO inks were inkjet printed and heated at different temperatures for different times. The films were studied by X-ray diffraction, scanning electron microscopy, resistivity measurements and ultraviolet–visible spectroscopy. The results demonstrated that 0.2 M AZO (2 at%) film heated at 250 °C for 120 min showed highly preferential growth along the c-axis, uniform microstructure with a resistivity of 0.03 Ω cm and high transmittance more than 90% in the visible range of the spectrum with an optical band gap at 3.326 eV.     

不同衬底上ZnO:Al透明导电薄膜的性能

室温下,采用射频磁控溅射法在玻璃和聚对苯二甲酸乙二醇酯（polyethylene terephthalate,PET）上沉积了掺铝的氧化锌（ZnO：Al,AZO）透明导电薄膜。通过X射线衍射仪分析不同衬底上AZO薄膜的结构,采用四探针测试仪及紫外可见光分光光度计测试薄膜的光电性能。结果表明：沉积在两种衬底上的AZO薄膜都具有六方纤锌矿结构,最佳取向均为[002]方向;玻璃衬底和PET衬底上制备的AZO薄膜的方阻分别为19/sq和45/sq,薄膜透光率均高于90%。实验表明,柔性衬底透明导电氧化物薄膜可以代替硬质衬底透明导电薄膜使电子器件向小型化、轻便化方向发展。     

W18O49/PET-ITO柔性电致变色薄膜制备及其变色性能

采用溶剂热法制备W18O49纳米线电致变色材料，喷涂在聚对苯二甲酸乙二醇酯?氧化铟锡(PET?ITO)(方阻35 Ω)柔性透明导电基底上得到柔性电致变色薄膜。采用X射线衍射仪、扫描电子显微镜、高分辨场透射电子显微镜和X射线光电子能谱对W18O49的微观结构和价态等进行表征，用电化学工作站与紫外?可见光分光光度计对W18O49/PET?ITO柔性电致变色薄膜的光学调制范围、响应时间和循环稳定性等进行了表征和分析。结果表明，光谱扫描波长?=633 nm时，W18O49/PET?ITO柔性电致变色薄膜的光学调制范围ΔT=23%。薄膜透光率变化90%时，着色和褪色时间分别为12.8和10.6 s。W18O49/PET?ITO柔性电致变色薄膜具有优异的循环稳定性，连续着色褪色循环3000 s薄膜透光率仍达80.9%。     

Optical and electrical properties of Al doped ZnO thin film with preferred orientation in situ grown at room temperature

To optimize the process and obtain highly conducting and transparent Aluminum-doped zinc oxide (AZO) thin films, AZO films were deposited on glass substrates at room temperature by Radio-frequency (RF) magnetron sputtering with various Argon flow rates. The influences of Argon flow rate on structure, morphology, optical, electrical and photoluminescence properties of AZO films were investigated by varying the Argon flow rate from 36 to 68 sccm. The best quality AZO film with resistivity 1.39 × 10⁻³ Ω cm, sheet resistance 8.2 Ω/sq and 84.2% average visible transmittance was prepared at 44 sccm for 30 min. Also, the self-heating effect of target was investigated by preparing AZO films for 10 min and 20 min at 44 sccm, 180 W and 1.0 Pa. The influence of increasing structural quality actually affected by Argon flow rate was more prominent on carrier concentration than mobility. The schematic illustration of microstructural evolution was proposed. The average growth rate of around 60 nm/min demonstrated the self-heating effect of target was weak and could be ignored.     

Preparation of poly(vinyl alcohol) films with promising physical properties in comparison with commercial polyethylene film

Poly(vinyl alcohol) (PVA) films with different thicknesses (0.08, 0.2, 0.23, 0.42 mm) were prepared by a casting technique. The transmission and the absorption of the PVA films were measured as functions of the wavelengths. PVA film with a thickness of 0.42 mm showed zero transmission in the wavelength range of 190–350 nm. The transmission spectrum of a commercial polyethylene film with a thickness of 0.21 mm was compared to the transmission spectrum of PVA film with a thickness of 0.42 mm. A correlation was found between the two transmission spectra in the region 190–350 nm and a 20% increase in the transmission of the PVA film in comparison with the transmission of commercial polyethylene in the region 350–1500 nm. The near‐infrared region of the transmission of commercial polyethylene was increased by 15% with respect to the transmission of the PVA film. The stress–strain measurements were done for PVA and commercial polyethylene films. The Young's modulus and the strength at break for PVA films are higher by two orders of magnitude than those for commercial polyethylene film. The strain at break for commercial polyethylene is 17% lower than that for PVA film. Radiation effects on the optical properties of PVA and commercial polyethylene films were investigated. The PVA and commercial polyethylene films were irradiated with a xeon arc lamp at 3.5–5 W/cm². The optical properties for PVA and commercial polyethylene films were studied after irradiation. The obtained results showed that PVA film with a thickness of 0.42 mm gave promising properties which could be used in technological applications. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1219–1226, 2002     

Investigation of optical modulated conductance effects based on a graphene oxide-azobenzene hybrid

An azobenzene (AZO) chromophore was covalently attached to graphene oxide (GO) through an amide linkage. The microstructure of the GO-AZO hybrid was characterized by microscopic and X-ray diffraction methods. An internal short-range ordered crystalline structure similar to graphite was observed. Spectroscopic evidence testified the strong electronic interactions between the AZO and GO in this GO-AZO hybrid system. Upon ultraviolet (UV) irradiation, the AZO moieties bonding on GO underwent a reversible trans-cis photoisomerization behavior. An optical modulated conductance of the GO-AZO film induced by the isomerization of the AZO chromophores was also monitored. The current showed a twofold increase after irradiation of UV light for 20 min.     

Optical waveguiding as a method for characterizing the effect of extended cure and moisture on polyimide films

Integrated optics techniques (i.e., guiding light through a thin film) have been used to study the effects of extended cure and moisture exposure on polyimide films as manifested in changes in the TE (in-plane) and TM (out-of-plane) refractive indices and in their difference (birefringence). Mechanical testing of these films has been done using the load-deflection technique. Du Pont polyimide Pyralin 2555 and 2556 (benzophenone tetracarboxylic dianhydride-oxydianiline/metaphenylene diamine), cured repeatedly at 400°C and 375°C respectively, show an increase in refractive index as a function of cure (possibly due to densification), as well as an increase in birefringence (due to increased residual stress). Upon exposure to moisture, the TM and TE refractive indices both increase (absorption of the polar water molecule), but the TE index does not increase as much. Mechanical testing has shown that the residual stress in the polyimide film increases with extended cure and decreases with moisture exposure due to moisture-induced swelling of the film. A model is proposed which relates the optical results to the mechanical measurements. Based on our data, a preliminary stress-optic coefficient is reported.     

Synthesis of high-quality AZO polycrystalline films via target bias radio frequency magnetron sputtering

The deposition rate, transmittance and resistivity of aluminium-doped zinc oxide (AZO) films deposited via radio frequency (r.f.) sputtering change with target thickness. An effective method to control and maintain AZO film properties was developed. The strategy only involved the regulation of target bias voltage of r.f. magnetron sputtering system. The target bias voltage considerably influenced AZO film resistivity. The resistivity of the as-deposited AZO film was 9.82×10⁻⁴ Ω cm with power density of 2.19 W/cm² at target self-bias of −72 V. However, it decreased to 5.98×10⁻⁴ Ω cm when the target bias voltage was increased to −112 V by applying d.c. voltage. Both growth rate and optical band gap of AZO film increased with the absolute value of target bias voltage – growth rate increased from 10.54 nm/min to 25.14 nm/min, and band gap increased from 3.57eV to 3.71 eV when target bias voltage increased from −72 V to −112 V at r.f. power density of 2.19 W/cm². The morphology of AZO films was slightly affected by the target bias voltage. Regulating target bias voltage is an effective method to obtain high-quality AZO thin films deposited via r.f. magnetron sputtering. It is also a good choice to maintain the quality of AZO film in uptime manufacturing deposition.     

Influence of ZnO buffer layer on AZO film properties by radio frequency magnetron sputtering

Transparent conductive films of Al-doped zinc oxide (AZO) were deposited on glass substrates under various ZnO buffer layer deposition conditions (radio frequency (r.f.) power, sputtering pressure, thickness, and annealing) using r.f. magnetron sputtering at room temperature. This work investigates the influence of ZnO buffer layer on structural, electrical, and optical properties of AZO films. The use of grey-based Taguchi method to determine the ZnO buffer layer deposition processing parameters by considering multiple performance characteristics has been reported. Findings show that the ZnO buffer layer improves the optoelectronic performances of AZO films. The AZO films deposited on the 150-nm thick ZnO buffer layer exhibit a very smooth surface with excellent optical properties. Highly c-axis-orientated AZO/ZnO/glass films were grown. Under the optimized ZnO buffer layer deposition conditions, the AZO films show lowest electrical resistivity of 6.75 × 10⁻⁴ Ω cm, about 85% optical transmittance in the visible region, and the best surface roughness of R_a = 0.933 nm.     

Development of warpage and residual stresses in film insert molded parts

Residual stresses, bending moments, and warpage of film insert molded (FIM) parts were investigated by experimental and numerical analyses. Thermally induced residual stresses in FIM parts were predicted by numerical simulations with both commercial and house codes. Bending moments and warpage of FIM tensile specimens were calculated numerically and compared with experimental results. Thermally induced residual stresses were predicted by utilizing a one‐dimensional thermoelastic model where constant material properties are assumed. The residual stress distribution depended remarkably on the Biot number and the heat was removed rapidly through the surface resulting in high residual stresses. Asymmetric residual stresses generated by nonuniform cooling of the part provoked nonuniform shrinkage and warpage of the molded tensile specimen. It was found that the numerically calculated bending moment is in good agreement with the experimental results. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers