Electron emission from Pb(Zr0.65Ti0.35)O3 film cathode by pulse electric field

Pulse electric field induced electron emission from the Pb(Zr_0.65Ti_0.35)O₃ ferroelectric films has been investigated as a function of the film thickness from 0.2 to 4.0 μm and the upper electrode diameter from 200 to 1100 μm. The electron emission charge from the 3.0 μm film was several nC per pulse, which was comparable to that of the bulk ferroelectrics. However, the local dielectric breakdown occurred in the films below 1.0 μm without the electron emission, which was confirmed by the optical microscopy observation after the emission tests. As the upper electrode size decreased and the film thickness increased, electrons were more easily emitted without breakdown.     

Synthesis and characterization of electrolyte-grade 10%Gd-doped ceria thin film/ceramic substrate structures for solid oxide fuel cells

In the present research, spray pyrolysis technique is employed to synthesize 10%Gd-doped ceria (GDC) thin films on ceramic substrates with an intention to use the "film/substrate" structure in solid oxide fuel cells. GDC films deposited on GDC substrate showed enhanced crystallite formation. In case of NiO-GDC composite substrate, the thickness of film was higher (~ 13 μm) as compared to the film thickness on GDC substrate (~ 2 μm). The relative density of the films deposited on both the substrates was of the order of 95%. The impedance measurements revealed that ionic conductivity of GDC/NiO-GDC structure was of the order of 0.10 S/cm at 500 °C, which is a desirable property for its prospective application.     

Optical properties of thermochromic VO2 thin films on stainless steel: Experimental and theoretical studies

Thermochromic films of VO₂ were deposited by DC reactive magnetron sputtering on stainless steel substrate. Complex refractive indexes of VO₂ were determined by ellipsometric spectroscopy (0.35-16.5 μm) for different film thicknesses. Optical simulations were performed to model the spectral reflectance of the film/substrate system for a film thickness of 100 nm and 200 nm and to monitor the optical contrast of the thermochromic layers by comparing the spectral reflectance at 25 °C and 100 °C. The good agreement observed between experimental and theoretical spectra demonstrates the adequacy of the model for predicting the optical properties of the samples.     

扰动情况下双油槽圆形轴瓦滑动轴承性能分析

采用FLUENT软件及其提供的气穴模型,计算了双油槽圆形轴瓦滑动轴承的油膜压力分布及气穴存在区域大小和位置,并同其他边界条件进行了对比;讨论了进油压力对轴承的流场和承载能力的影响;利用自行改进的动网格技术对轴颈扰动速度对流场和油膜力的影响进行了非稳态计算。计算结果表明,进油压力对油膜力的影响较大,油膜压力受轴颈扰动速度的影响很大,油膜力与轴颈扰动速度明显呈非线性关系,利用改进的动网格技术可以很好地对轴承的动特性进行分析。论文为今后大扰动条件下转子-轴承系统的非线性动特性分析打下了基础,为滑动轴承的设计提供了一种理论参考依据     

Microstructure and electrochemical properties of magnetron-sputtered LiCoO2/LiNiO2 multi-layer thin film electrode

LiCoO₂ single-layer and LiCoO₂/LiNiO₂ multi-layer thin film electrodes were successfully fabricated by magnetron sputtering. Their microstructure and electrochemical properties were investigated. Once annealed, both films had the (0 0 3) preferred orientation to minimize the surface energy. The initial discharge capacity of the multi-layer thin film was approximately 53.1 μAh/cm² μm, which was higher than that of the LiCoO₂ single-layer thin film having similar thickness. The capacity retention of the multi-layer thin film was superior to that of the single-layer thin film. These findings indicate that the multi-layer thin film is a promising cathode material for the fabrication of high-performance thin film batteries.     

A study of the effect of filler metal thickness on tensile strength for a stainless steel plate-fin structure by experiment and finite element method

This paper presents a study of the effect of filler metal thickness on tensile strength for a stainless steel plate-fin structure by finite element method and experiment. The results show that the filler metal thickness has a great effect on tensile strength. The tensile strength is increased with the filler metal thickness increase, then it keeps stable when the filler metal thickness is 105–140 μm. But it decreases rapidly when the filler metal thickness is larger than 140 μm. The fracture location is shown at the end of vertical fin when the filler metal thickness is 105–140 μm. Specimens with filler metal thickness smaller or larger than 105–140 μm rupture in the brazed filler metal. The optimal filler metal thickness is 105 μm, using which can get higher strength for 304 stainless steel plate-fin structures.     

Electrical, photoelectrical, and photoelectrochemical properties of electrodeposited CdTe films subjected to high-energy irradiation

The general goal of this work is to study the structure and photoelectrical properties of the electrochemically deposited thin CdTe films. The conducted investigation has shown that (i) as-deposited films have the single-phase structure with a grain size of 1-10 μm and are of the n-type conductivity; (ii) photosensitivity abruptly decreases when the film thickness is over 10 μm; (iii) annealing at temperatures less than 500 °C improves the film quality with retention of the n-type conductivity; and (iv) photosensitivity of the films is not impaired under irradiation by 6 MeV electrons with a fluence of 5 × 10¹⁴ cm^− 2.     

Fabrication and characterization of novel nanostructured copper oxide films via a facile solution route

Nanostructured CuO film was prepared using glass or stainless steel slices as substrate via a simple ammonia-assisted solution route at 60 °C. The obtained CuO film was made up of well-crystallized nanosheets of 50-360 nm in thickness and 0.7-4.5 μm in width. The reaction time and the substrate have significant effects not only on the thickness, width, arrangement of the nanosheets but also on the morphology and the thickness of the films. The CuO film was characterized by SEM, TEM, XRD, IR, and Raman spectroscopy techniques.     

Enhanced light absorption of Ag films deposited onto femtosecond laser microstructured silicon

Absorptive properties of silver (Ag) films with the thickness varied from 160 nm to 340 nm deposited onto the surface of femtosecond laser microstructured silicon by vacuum thermal evaporation were measured in a wavelength range of 0.3-16.7 μm. Greatly enhanced light absorption of Ag films has been observed in the whole measured wavelength range. For the same Ag film thickness (268 nm), the light absorption was strongly depended on the height and spacing of the spikes, especially in the region of 1-16.7 μm. The relation between light absorption and thickness of Ag films has also been investigated, it was shown that the light absorption decreases with the increasing thickness of Ag films. The strongly enhanced light absorption in such a wide wavelength range is mainly ascribed to the multiple reflection of light between spikes and surface plasmon excitation of noble metal nano-particles on the spikes surface.     

Carbon coatings on silica glass optical fibers studied by reflectance Fourier-transform infrared spectroscopy and focused ion beam scanning electron microscopy

Carbon coatings applied on optical fibers via chemical vapor deposition were characterized by a resistance technique, focused ion beam/scanning electron microscopy (FIB/SEM), and reflectance Fourier-transform infrared spectroscopy (FTIR). The resistance technique measures the thickness of carbon film by measuring the resistance over a section of optical fiber, and backing out the film thickness. The FIB/SEM system was used to remove a cross section of the optical fiber and carbon coating and using a scanning transmission electron detector the thickness was measured. The FTIR approach is based on the fact that the wavelength of the light in the mid-infrared region (~ 10 μm) is significantly larger than the typical thickness of the carbon coatings (< 0.1 μm) which makes the coating “semi-transparent” to the infrared light. Carbon coating deposition results in significant transformations of the band profiles of silica in the reflectance spectra that were found to correlate with the carbon coating thickness for films ranging from 0.7 nm to 54.6 nm. The observed transformations of the reflectance spectra were explained within the framework of Fresnel reflection of light from a dual-layer sample. The advantage of this approach is a much higher spatial resolution in comparison with many other known methods and can be performed more quickly than many direct measurement techniques.     

Determination of the thickness of metal coatings on granular diamond materials by spatially resolved optical methods

The embedding of surface-modified granulates into metallic matrices is a promising way to optimize the interface matrix/granulate in respect to mechanical and thermal properties. In the case of surface modification by coating, a reliable determination of the coating thickness on granulates is desirable, since the interface properties may depend on it to a critical extent. This paper proposes a simple method to determine the thickness of transparent metal coatings on diamond substrates. Diamond granulates with grain sizes between 100 and 120 μm were coated with molybdenum in an intermixing device which allows reasonable film uniformity on granulates. The deposition method was single source DC magnetron sputtering with argon as working gas. By comparing the transmission of the uncoated and coated diamonds with an optical scanner, the coating thickness could be determined from the known extinction coefficient. A good correlation between the measured film thicknesses and the deposition time was achieved. It can be concluded therefore, that the presented method is a viable and cost-efficient way for the determination of the average thickness of transparent metallic coatings on a sample of transparent granular substrates, with an estimated minimum and maximum measurable thickness of 2.5 nm and 15 nm respectively for molybdenum.     

Photovoltaic characterization of Copper-Indium-Gallium Sulfide (CIGS2) solar cells for lower absorber thicknesses

Chalcopyrites are important contenders among thin-film solar cells due to their direct band gap and higher absorption coefficient. Copper-Indium-Gallium Sulfide (CIGS2) is a chalcopyrite material with a near-optimum band gap of ~ 1.5 eV. Record efficiency of 11.99% has been achieved on a 2.7 μm CIGS2 film prepared by sulfurization at the Florida Solar Energy Center (FSEC) PV Materials Lab. In this work, photovoltaic performance analysis has been carried out for a 1.5 μm absorber prepared under similar conditions as that of a 2.7 μm thick absorber sample. It was observed that there is an increase in diode factor and reverse saturation current density when the absorber thickness was decreased. The diode factor increased from 1.69 to 2.18 and reverse saturation current density increased from 1.04 × 10^− 10 mA/cm² to 1.78 × 10^− 8 mA/cm². This can be attributed to a decrease in the grain size when the absorber thickness is decreased. It was also observed that there is an improvement in the shunt resistance. Improvement in shunt resistance can be attributed to optimized value of i:ZnO for lower absorber thickness and less shunting paths due to a smoother absorber.     

Development of a low-temperature He compressor for superfluid He-He mixtures

The development, testing and modeling of a “compressor” that is capable of increasing the concentration of the ³He component of a liquid superfluid ³He-⁴He mixture is discussed. This compressor was developed to drive refrigeration cycles for cooling below 1 K. The compressor design and performance testing is described in detail. The compressor was operated at 1.2 K and ³He molar flow rates of 130 μmol/s were achieved. Compression ratios in excess of 6 were also demonstrated. The theoretical models presented are used to estimate the expected efficiencies of the compressor as well as the effect of the ⁴He component on the power required to drive the compressor.     

Simulation based performance comparison of transistors designed using standard photolithographic and coarse printing design specifications

In this work a simulation based comparative study of organic field effect transistors designed using standard lithographic and printing designs is presented. The device simulations were performed using two-dimensional drift-diffusion equations with a Poole-Frenkel field dependent mobility model. Both photolithographic and coarse printing transistor designs employed common materials such as 150 nm thick pentacene, 150 nm thick parylene gate insulator, gold source-drain electrodes and aluminum gate electrodes. The major differences between the two fabrication specifications are the minimum source/drain line width and the transistor channel length. The typical specifications for the minimum line width and channel length were 2 μm and 5 μm for photolithography and 25 μm and 20 μm for coarse printing techniques, respectively. The gate, source, and drain capacitances and channel on-resistances at various channel lengths and gate overlaps have been extracted and presented specifically for both process schemes. Due to increased channel length and gate-source/drain overlap of printed electrodes relative to lithographic design, the resulting on-resistance and capacitances for coarse printing are significantly higher. These results demonstrate a substantial operating frequency reduction for printing design relative to photolithographic design. For the tested materials and designs it is shown that the cut-off frequency for the photolithographic process was 400 kHz but decreased to a much lower 26 kHz for the coarse printing process. Since printing technology uses various other materials, which typically have less performance than the ones used for this simulation, the actual printed device might have even lower performance than predicted here.     

Polyaniline micropattern onto flexible substrate by vapor deposition polymerization-mediated inkjet printing

An approach to pattern a conducting polymer on various flexible substrates using vapor deposition polymerization-mediated inkjet printing method was demonstrated. Complex patterns of doped emeraldine salt polyaniline were obtained via chemical oxidation polymerization of vaporized aniline monomer on inkjet-printed oxidant patterns. The features of pattern were precisely controlled by inkjet printing with a micrometer-scale resolution. Fourier transformed infrared attenuated total reflection analysis was conducted in order to confirm the polymerization of aniline monomer and UV-visible spectroscopy analysis was used to investigate the oxidation state of obtained polyaniline. The minimum width of patterned line was ca. 80 μm. The sheet resistance of patterned polyaniline films was 3.8 × 10³ Ω/□ for an average patterned film thickness of ca. 450 nm.     

On the ultraviolet light induced oxidation of amorphous As2S3 film

Illumination of amorphous As₂S₃ film by ultraviolet light with an overall light intensity on the sample surface of around 10 W cm^− 2 leads to extensive film oxidation. After 2 min of illumination most of As₂S₃ film of an original thickness at around 0.425 μm was converted into a cubic form of As₂O₃-arsenolite. A considerable amount of arsenolite microcrystals were found at a height of around 2 μm and more which indicated a growth of As₂O₃ microcrystalline particles from the vapor phase.     

Unified surface anchoring strength from the splay elastic deformation in nematic slabs

Film thickness dependences of the unified surface anchoring strengths from the splay deformation for nematic cells were discussed. Thin nematic parallel (d = 2-50 μm) and wedge (d = 0.3-5 μm) cells with the same solid surface were prepared to evaluate the surface anchoring strength. The surface anchoring strengths from the splay deformations for two kinds of liquid crystals were measured by using the saturation method. The nematogens used were 4-pentyl-4′-cyanobiphenyl and mixture compound ZLI-4792 (Merck Japan Co., Ltd.) with positive dielectric anisotropy. Film thickness dependence of the surface anchoring strength was elucidated on the basis of the conventional ionic surface polarization. It was also discussed that a surface anchoring strength from the splay deformation is to be an intrinsic value defined at an interfacial region and not a value changing with the film thickness.     

Etching processes of transparent carbon nanotube thin films using laser technologies

Carbon nanotubes (CNTs) have potential as a transparent conductive material with good mechanical and electrical properties. However, carbon nanotube thin film deposition and etching processes are very difficult to pattern the electrode. In this study, transparent CNT film with a binder is coated on a PET flexible substrate. The transmittance and sheet resistance of carbon nanotube film are 84% and 1000 Ω/□, respectively. The etching process of carbon nanotube film on flexible substrates was investigated using 355 nm and 1064 nm laser sources. Experimental results show that carbon nanotube film can be ablated using laser technology. With the 355 nm UV laser, the minimum etched line width was 20 μm with a low amount of recast material of the ablated sections. The optimal conditions of laser ablation were determined for carbon nanotube film.     

Mechanical characterization of LiPON films using nanoindentation

Nanoindentation has been used to characterize the elastic modulus and hardness of LiPON films ranging in thickness from 1 to 10 μm. Four fully dense, amorphous films were deposited on glass and sapphire substrates with one film annealed at 200 °C for 20 min. The modulus of LiPON is found to be approximately 77 GPa, and argued to be independent of the substrate type, film thickness, and annealing. Based on the numerical analysis of Monroe and Newman, this value may be sufficiently high to mechanically suppress dendrite formation at the lithium/LiPON interface in thin film batteries [1]. Using Sneddon's stiffness equation and assuming the modulus is 77 GPa, the hardness is found to be approximately 3.9 GPa for all but the annealed film. The hardness of the annealed film is approximately 5% higher, at 4.1 GPa. Atomic force microscopy images of the residual hardness impressions confirm the unexpected increase in hardness of the annealed film. Surprisingly, the indentation data also reveal time-dependent behavior in all four films. This indicates that creep may also play a significant role in determining how LiPON responds to complex loading conditions and could be important in relieving stresses as they develop during service.     

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.