Electron beam evaporated carbon nanotube dispersed SnO2 thin film gas sensor

Carbon nanotube (CNT) is a useful material for gas-sensing applications because of its high surface to volume ratio structure. In this work, multi-wall CNTs are incorporated into tin oxide thin film by means of powder mixing and electron beam evaporation and the enhancement of gas-sensing properties is presented. The CNTs were combined with SnO₂powder with varying concentration in the range of 0.25–5% by weight and electron beam evaporated onto glass substrates. From AFM and TEM characterization, CNT inclusion in SnO₂thin film results in the production of circular cone protrusions of CNT clusters or single tube coated with SnO₂layer. Experimental results indicate that the sensitivity to ethanol of SnO₂thin film increases by the factors of 3 to 7, and the response time and recovery time were reduced by the factors of 2 or more with CNT inclusion. However, if the CNT concentration is too high, the sensitivity is decreased. Moreover, the CNT doped film can operate with good sensitivity and stability at a relatively low temperature of 250–300^∘C. The improved gas-sensing properties should be attributed to the increasing of surface adsorption area of metal oxide produced by CNT protrusion.     

Study of poling methods for multilayer pyroelectric thin film infrared detectors

The multilayer pyroelectric thin film infrared detector arrays were prepared by a metallo-organic compound decomposition method. A DC poling and a pulse poling methods have been investigated to reduce the poling time and improve the poling efficiency of pixels of an uncooled infrared focal plane array. It’s found that the efficiency of the DC poling increased by 20% via optimizing the poling conditions. While the efficiency of the pulse poling increased by over 31%. Compared with the DC poling, the pulse poling can improve poling efficiency and reduce the poling time significantly. Furthermore, a stepwise pulse field can reduce the breakdown of thin films during poling.     

电子束固化技术及可电子束固化环氧树脂体系

论文综述了电子束固化树脂基复合材料技术的特点及其在国内外的研究及发展状况 ,并介绍了可电子束固化的环氧树脂和光引发剂及其阳离子固化机理 ;具体地描述了经电子束固化的树脂浇铸体及复合材料的性能。     

Ion beam synthesis of SiC thin films

This report reviews irradiation effects of 2 MeV He⁺, Ne⁺, and Ar⁺ ions on the film structure of the carbon-film/Si-substrate system. Using ion irradiation, an epitaxial silicon carbide (SiC) film is grown at atmospheric temperature on a Si substrate. The SiC formation is achieved with appropriate thickness of the initial carbon film. Kinetic analyses of the ion dose dependence of the SiC formation reveal that the SiC film thickness evolution process includes three stages. The first is a steep increase of the SiC, which is governed by inelastic collision. The second is a gentle increase of the SiC, which is governed by diffusion. The last is a decrease of the SiC, which is caused by sputtering. The SiC formation mechanism is also discussed.     

Electrical conductivity in thin layers of chitosan and chitosanacetate

The present work is concerned with experimental results on the electrical conductivity of chitosan and chitosan acetate in the temperature range 20 to 325 K, and a broad range of electric field strength. The thickness of the layers was ~15 μm. The influence of the internal structure on electrical properties was observed. The mechanism of the electrical conductivity was controlled by the Poole-Frenkel effect with contribution of hopping or tunneling from deep traps     

Electron beam pumped argon-excimer laser using an unstableresonator

An unstable resonator was used for an e-beam pumped argon-excimer laser in the VUV-spectral region, for the first time to our knowledge. Adoption of the unstable resonator achieved successful operations of the high output energy of 28 mJ without any damage of the resonator mirrors. Beam divergence of the argon-excimer laser output was measured with a beam profiler, which was developed in our laboratory, It was found that the output beam involved a large ASE output. The maximum focused fluence at the center of the output beam was measured to be 42 mJ/cm². The coherence of the argon-excimer laser was degraded by the ASE, which was caused due to high gain condition of the argon-excimer laser     

Electron emission from PZT ceramic thin plate by pulsed electric field

Abstract

Electron emission into vacuum from a thin plate of ferroelectric lead-zirconatetitanate (PZT) ceramic has been observed under the impression of electric field of pulse consisting of a pair of positive and negative voltages. The emission was observed at pressure lower than about 10^?1 Torr. The emitted charge increases with increasing the positive and the absolute negative voltages of the pulse and the collector voltage. The minimum absolute value of the negative pulse for electron emission is 30V when the positive voltage is larger than 150V. The maximum peak current density is 70A/cm². It is considered from the electrode area and thickness dependences of the charge that electrons are emitted not only from the ceramic surface near the electrode edge but also through the thin metal electrode. The emitted charge per one pulse little depends on pulse frequency when it is less than 2kHz, and so the total current density can be enhanced by increasing the frequency. The emission is observed even at temperatures above Curie temperature. It is considered that the emission is induced by abrupt change of dielectric flux as well as the polarization reversal. Cathodoluminescence from phosphors excited by the emitted electrons has been observed.     

Interfacial layers and their effect on leakage current in mocvd-deposited SBT thin films

Abstract

Strontium bismuth tantalate (SBT) thin films were deposited on Pt/Ti electrodes by metalorganic chemical vapor deposition (MOCVD). Interactions at the interface of Pt and SBT and their effect on leakage current were investigated. High-resolution transmission electron micrographs (HRTEM) reveal that after annealing at 700°C, a 1–2 nm thick interfacial layer built. Auger electron spectra (AES) confirm that the constituents of SBT intermix with the Pt and vice versa. Schottky emission yields a nice linear fit to the leakage current data but the extracted values of the optical dielectric constant and the Richardson constant do not meet experimental values. Taking into account an interfacial layer with low dielectric constant and the effect of diffusion on the Schottky emission these inconsistencies can be resolved.     

Fabrication of polyurea thin films for optical second-harmonicgeneration by vapor deposition polymerization. Effects of poling fieldand monomer structure on reactivity and SHG performance

Aromatic PU (polyurea) thin films were fabricated for second-order nonlinear optical application by vapor deposition polymerization using MDI (4,4-diphenylmethane diisocyanate) and DDM (4,4-diaminodiphenylmethane) or DNB (p-diamino nitro benzene). The former was abbreviated to PU (DDM) and the latter to PU (DNB). In PU (DDM) fabricated by VDP (vapor deposition polymerization), the SH (second-harmonic) intensity showed orientation stability up to 200°C due to polymerization and simultaneous orientation under the dc field (the poling process). In PU (DNB) fabricated by VDP, although the enhanced optical nonlinearity due to the introduction of the NO₂ group was achieved, a drastic decay of SH intensity was observed at 200°C. The decay was attributed to hindrance of the polymerization by the dc field, suggesting that the strong poling field reduces reactivity of some monomers. In PU (DNB) fabricated by EVDP (VDP under electric field), SHG (second-harmonic generation) was observed. Applying a higher electric field was effective in improving the optical nonlinearity. Film fabrication at higher temperature was also effective in improving the orientation stability and the optical nonlinearity, due to further polymerization during fabrication. We attributed this to the increase in the number of urea groups. The use of appropriate monomers that polymerize under high electric fields would result in improvement of SHG characteristics     

Electron mobility in silicon and germanium inversion layers: The role of remote phonon scattering

We calculate the electron mobility in Si and Ge inversion layers in single-gate metal-oxide-semiconductor field effect transistors. Scattering with bulk phonons, surface roughness and remote phonons is included in the mobility calculations. Various high-κ dielectric materials are considered for both Si and Ge substrates. Overall, Ge outperforms Si, but in general Ge is more affected by the use of high-κ dielectrics. HfO₂ degrades the mobility substantially compared to SiO₂ for Si substrates and may prohibitively degrade performance. HfO₂ with Ge yields an improvement over Si with a mobility enhancement ≈3× at an electron sheet density of 1×10¹³ cm⁻³.     

含氟聚合物胶粘剂及其电化学特性的研究

为了研究锂离子电池用含氟胶粒剂并了解其电化学特性,采用差热力析（ＤＴＡ）、扫描电镜（ＳＥＭ）以及三电极（加参比电极）实验电池充放电循环等手段,对锂离子电池电极材料成型用的昌氟聚合物胶粘剂的配方、胶层干燥（熔结）方法、胶层的粘接强匿、耐电解质性能以及该胶粘剂作为粘结别的石墨电极的电化学特性等进行了研究。研穷结果表明：以聚偏氯乙烯为基料溶解于Ｎ－甲基吡咯烷酮或二甲基乙酰胺的胶粘剂有较好的粘合力,对铜片的粘合剪切强度为７．１ＭＰａ－８．３ＭＰａ,对铝片的粘合剪切强匿为１．５ＭＰａ－１．８ＭＰａ。通过ＤＴＡ法测定聚偏氟乙烯的熔融温度,确定了上述胶粘剂的干燥熔结果件为６０℃×４ｈ＋１８０Ｃ×１０ｍｉｎ。干燥烧结后的粘结试样经电解液（ＥＣ＋ＤＥＣ）浸泡７天后,粘合强度的保持率为初始的３３％。用该胶粘剂制成石墨电极并装配成实验电池进行充放电实验,经过１０次充放电循环后,其平均比容量为１９５ｍＡｈ／ｇ。     

Non-uniform electric field in poling of structurally graded monolithic piezoactuator

In this paper the effect of a non-uniform electric poling field and its optimisation for structurally graded piezoelectric actuators are investigated. The two compared actuator structures were both based on commercial PZT 5H bulk discs with thicknesses of 375 µm (Ø 25 mm), where one was machined into a graded structure with a step-like decrease of the thickness towards the centre and one intact. The hysteresis loops of the pre-stressed concave shaped actuators were measured under 0.5–5.0 kV/mm electric fields at 25–100°C temperatures, and the remanent polarization and coercive electric field were determined. The graded structured actuator obtained ～10% higher coercive field compared to the non-graded actuator, when measured at 25°C and 5.0 kV/mm. On the other hand the remanent polarisation values of the graded actuator were slightly lower than non graded bulk values. However the maximum decrease was only 9.6% under 5.0 kV/mm. The results show that strain and stress gradients in the structure are generated when exposed to an electric field. Furthermore, as a consequence of the restricted dimension changes, an inherent bending of the monolithic ceramic structure was obtained which can be utilised, for example, in miniaturised micro-machined actuators or in larger pre-stressed benders.     

Structural and dielectric properties of epitaxial Ba0.6Sr0.4TiO3 thin films grown on Si substrates with thin SrO buffer layers

(100) epitaxial Ba_0.6Sr_0.4TiO₃ (BST) thin films were grown on Si substrates using a 9 nm thick SrO buffer layer. The phase shifter fabricated on BST films grown on a SrO buffered Si substrate showed a larger figure of merit (FOM) of 24.7°/dB as a result of improving the phase tuning while retaining an appropriate insertion loss compared to that (15.3°/dB) for the BST/MgO structure. This work demonstrates that a thin SrO buffer layer plays an important role in the successful integration of BST-based microwave tunable devices onto Si wafers.     

Production of thin, uniform toner layers through use of a contactblade with mono-component development systems

The authors focus on the effects of contaminants on the uniformity of the toner layers resulting from the direct observation of the toner flow and metering phenomena. The authors have improved earlier observation methods to observe directly and analyze the toner transportation and toner behavior in the layer thickness control area. Using the improved method, they have experimented with the various kinds of toner transportations and layer thickness control systems. They concentrated on disruption of toner layers by contaminant infiltration and found that static toner and friction force against the toner on the developing sleeve are most important in preventing a contaminant from entering the metering area. Based on these results, they found a highly stable layer-forming method, called the contact blade method. which minimizes the effects of infiltration by contaminants     

Preparation and properties of sputtered lead titanate thin films on MgO single crystals and mgo buffer layers

Abstract

By means of planar multitarget sputtering (001) oriented PbTiO₃ films were deposited onto highly preferred (100) oriented platinum electrodes on (100) MgO single crystal substrates. Single phase perovskite type films with a degree of (001) orientation between 60% and 70% have been sputtered at substrate temperatures as low as about 470°C. The as grown films exhibit a dielectric constant in the range of 120 to 140 and a pyroelectric coefficient of about 20 nCcm^?2K^?1 at room temperature. The dielectric loss is about 0.01 at frequencies from 1 to 10 kHz. (100) GaAs substrates with an evaporated, highly oriented (100) MgO buffer layer were also used as substrates. However, on these substrates the platinum bottom electrode did not grow highly oriented though the same deposition parameters for Pt deposition as in the case of the single crystalline MgO substrate were used. That's why PbTiO₃ was produced with a lower (001) preferred orientation. Therefore, the dielectric constant is higher (170–190) and the pyroelectric coefficient is lower (12 nCcm^?2K^?1).     

Cu和Cr缓冲层对SmCo_5薄膜微观结构和磁性能的影响

利用新型AE(Advanced Energy)脉冲电源采取共溅射的方式在Si片上制备不同结构的Cr/SmCo_5/Cr和Cu/SmCo_5/Cr薄膜,并分别研究Cu和Cr缓冲层对SmCo_5薄膜磁性能和微观结构的影响。以Cu作为缓冲层时,在优于2×10―5Pa的真空环境下通过对样品在650℃退火60min,可以获得较良好的硬磁性能,垂直膜面的矫顽力可以达到1308Oe。以Cr作为缓冲层时,在低于2×10~(-5)Pa的真空环境中,且在650℃退火60min便制备出样品。随后分别改变Cr缓冲层的厚度和SmCo_5的厚度并观察其对Cr/SmCo_5/Cr的磁性能的影响。     

Influence of poling and annealing on the nonlinear dielectricpermittivity of PVDF-TRFE copolymers

The linear and second order permittivities of as-prepared and annealed, poled and unpoled PVDF-TRFE 56/44 mol% copolymer film are investigated as a function of temperature. In contrast to annealed PVDF-TRFE, the linear permittivity of unannealed PVDF-TRFE and its temperature dependence is not influenced by poling. This effect can be explained by the existence of domain walls in the crystalline regions of annealed samples, while the smaller crystallites in unannealed samples are always in a single domain state. Thus the poling degree dependence of the linear permittivity of annealed samples may therefore be an effect of domain wall motion. The second order permittivity is a measure of the remanent polarization. Samples poled before the first annealing exhibit a small persistent polarization that remains stable in the paraelectric phase, in contrast to samples which remain unpoled before annealing. This non-switchable polarization is unchanged after several heating cycles and even after poling in the opposite direction. An explanation for this fixed polarization are non-switchable dipoles which form an intermediate phase between the crystalline and the amorphous phase     

High-deposition-rate growth of PZT thin films by reactive electron beam coevaporation using Ti/Zr alloy

Abstract

Lead zirconate titanate (PZT) thin films were prepared by coevaporation of titanium/zirconium alloy and lead metal with an electron beam gun. Each of evaporation rates was independently controlled by each quartz crystal thickness monitor. Titanium/zirconium alloy was used because of simplicity of chemical composition control. To promote oxidation of the films, a mixed gas of oxygen and ozone (5%) was used. When evaporation rates of titanium/zirconium alloy and lead metal were controlled moderately, perovskite phase PZT film was obtained on 50 nm-thick-PbTiO₃-film at substrate temperature of 550°C. When atomic ratio of titanium/zirconium alloy was 50:50, chemical composition of the films was Ti:Zr = 9:1. Deposition rate was greater than 50 nm/min, which was much larger than that by the sputtering method.     

Effect of seed layers on dielectric properties of Ba(Zr0.3Ti0.7)O3 thin films

The Barium zirconium titanate Ba(Zr_0.3Ti_0.7)O₃ thin films were prepared on Pt/Ti/SiO₂/Si substrates with seed layers at the BZT/Pt interface by sol–gel process. Microstructure and structure of thin films were examined. Dielectric properties of thin films with various seed layers thicknesses were investigated as a function of frequency and direct current electric field. The tunability and dielectric constant of BZT thin films increased with increasing seed layer thickness from 0 to 20 nm, while it decreased with a further increase in thickness above 20 nm, meanwhile, the leakage current showed the similar tendency at applied electric field of 250 kV/cm. The optimized seed layer thickness for BZT thin films plays an important role in maintaining the high tunability and low leakage current, which are suitable for microwave device applications.