Effect of energetic electron beam treatment on Ga-doped ZnO thin films

Transparent conductive zinc oxide (ZnO) thin films were synthesized by a sol–gel spin coating method with the addition of Ga(NO₃)₃ in a Zn(CH₃COO)₂ solution and exposed to electron beam treatment. The UV–Vis spectra demonstrated that all of the films had transmittances of over 85% in the visible region. When Ga(NO₃)₃ was added to the ZnO precursor solution, the resistivity of the ZnO thin film decreased and the carrier concentration increased significantly. After electron beam treatment was performed on the 0.4 at.% Ga-doped ZnO film, the optical band gap increased and the resistivity significantly decreased resulting from the increases of the carrier concentration and mobility. By combining Ga doping and electron beam treatment, the resistivity of the ZnO thin film was reduced by a factor of nine hundred.     

A variable electron beam and its irradiation effect on optical and electrical properties of CdS thin films

A low energy electron accelerator has been constructed and tested. The electron beam can operate in low energy mode (100 eV to 10 keV) having a beam diameter of 8–10 mm. Thin films of CdS having thickness of 100 nm deposited on ITO-coated glass substrate by thermal evaporation method have been irradiated by electron beam in the above instrument. The I–V characteristic is found to be nonlinear before electron irradiation and linear after electron irradiation. The TEP measurement confirms the n-type nature of the material. The TEP and I–V measurements also confirm the modification of ITO/CdS interface with electron irradiation.      

Gradients of topographical structure in thin polymer films

We report the fabrication of centimeter-long gradients of topography. Structured polymer thin films were made by spin-coating an immiscible poly(methyl methacrylate)/poly(2-vinylpyridine) (PMMA/P2VP) blend from a common solvent on a substrate presenting a surface-energy gradient. Due to the interplay between polymer-wetting of the substrate and polymer phase-separation, different morphologies were observed along the sample. Atomic force microscopy (AFM) revealed a gradual transition from a flat to a structured morphology as the surface energy of the substrate was reduced. The transition occurred for a well-defined range of surface energies. A selective solvent was used to remove one of the polymer phases, increasing the topographical contrast and providing insight into the different stages of the transition. Image analysis allowed a quantitative characterization of the structure gradient.     

Surface energy modification by electron beam

We observe a pronounced variation of wettability properties in solid state materials induced by a low-energy electron beam. The phenomenon occurs in several stages characterized by various mechanisms. We show that for low electron doses the irradiation leads to decrease in the wetting of a dielectric surface due to induced surface electric potential. The higher electron charge leads to formation of a chemical monolayer on material’s surface. It has been found that the electron irradiation strongly modifies the surface free energy of SiO₂ by decreasing its total surface free energy value, almost twice. However, electron-induced variations of dispersive and polar components of the surface free energy are quite different and depend of incident electron charge.     

Analysis of microscopic parameters of surface charging in polymer caused by defocused electron beam irradiation

The relationship between microscopic parameters and polymer charging caused by defocused electron beam irradiation is investigated using a dynamic scattering-transport model. The dynamic charging process of an irradiated polymer using a defocused 30 keV electron beam is conducted. In this study, the space charge distribution with a 30 keV non-penetrating e-beam is negative and supported by some existing experimental data. The internal potential is negative, but relatively high near the surface, and it decreases to a maximum negative value at z = 6 μm and finally tend to 0 at the bottom of film. The leakage current and the surface potential behave similarly, and the secondary electron and leakage currents follow the charging equilibrium condition. The surface potential decreases with increasing beam current density, trap concentration, capture cross section, film thickness and electron–hole recombination rate, but with decreasing electron mobility and electron energy. The total charge density increases with increasing beam current density, trap concentration, capture cross section, film thickness and electron–hole recombination rate, but with decreasing electron mobility and electron energy. This study shows a comprehensive analysis of microscopic factors of surface charging characteristics in an electron-based surface microscopy and analysis.     

Enhanced photoluminescence of conjugated polymer thin films on nanostructured silver

Photoluminescence of a conjugated polymer in the presence of surface plasmons on metallic nanoparticles is studied. A layered device structure was constructed that enabled control over nanoparticle diameter and separation between the polymer and nanoparticles layers. The dependence of the surface plasmon evanescent field and energy transfer has been investigated with the largest enhancement in photoluminescence observed at a 40 nm distance separation between the fluorophore and the surface plasmon. A spectrum of surface plasmon resonances ranging from the emission to the absorption energies of the conjugated polymer revealed largest enhancements when the resonance was tuned to the conjugated polymer emission energy. At peak photoluminescence the maximum photoluminescent enhancement was found to be 5.6 times of the photoluminescence of the control structure and the total integrated enhancement was 5.9 times.     

Microstructural analysis of TiC reinforced ferrous surface composites processed by accelerated electron beam irradiation

The present study aims to analyze microstructures of TiC reinforced ferrous surface composites processed by accelerated electron beam irradiation. Two kinds of powder/flux mixtures, i.e., TiC and (Ti + C) powders with 40 wt% of CaF₂ flux, were deposited evenly on an AISI 304 stainless steel substrate, which was then irradiated with electron beam. TiC agglomerates and pores were found in the surface composite specimen processed by irradiation of TiC powders because of insufficient melting of TiC powders. In the specimen processed by irradiation of Ti and C powders having lower melting points than TiC powders, a lot of large TiC carbides were precipitated in the melted region, together with a few TiC agglomerates or pores. This indicated the more effective TiC precipitation obtained from the melting of Ti and C powders, instead of TiC powders. The hardness of the surface composite layer was about two times higher than that of the AISI 304 substrate mainly due to the precipitation of TiC carbides.     

电子辐照致VO_2(B)薄膜结构与红外光谱改变

本文以能量为1.0 MeV的电子束辐照VO2(B)薄膜,对电子辐照在薄膜中产生的缺陷进行了理论计算,使用X射线衍射仪、傅立叶中红外光谱仪对薄膜进行测试,分析了电子辐照对薄膜结构与红外光谱(3400~400 cm-1)的影响。结果显示:电子辐照可以在薄膜中引入点缺陷并产生退火效应,电子辐照在薄膜中引入的点缺陷,可以使V-O=V受到破坏,退火可以使V-O=V振动得到恢复,而电子辐照对薄膜八面体角度弯曲振动影响不大。     

Thermal and optical properties of electron beam irradiated cellulose triacetate

Samples from Cellulose triacetate (CTA) sheets were irradiated with electron beam in the dose range 10–200 kGy. Non-isothermal studies were carried out using thermogravimetric analysis (TGA) to obtain the activation energy of thermal decomposition for CTA polymer. The CTA samples decompose in one main break down stage. The results indicate that the irradiation by electron beam in the dose range 80–200 kGy increases the thermal stability of the polymer samples. Also, the variation of melting temperatures with the electron dose has been determined using differential thermal analysis (DTA). The CTA polymer is characterized by the appearance of one endothermic peak due to melting. It is found that the irradiation in the dose range 10–80 kGy causes defects generation that splits the crystals depressing the melting temperature, while at higher doses (80–200 kGy), the thickness of crystalline structure (lamellae) is increased, thus the melting temperature increases. In addition, the transmission of these samples in the wavelength range 200–2500 nm, as well as any color changes, were studied. The color intensity ΔE* was greatly increased on increasing the electron beam dose, and accompanied by a significant increase in the blue color component.      

Microstructure and surface morphology of YSZ thin films deposited by e-beam technique

In present study yttrium-stabilized zirconia (YSZ) thin films were deposited on optical quartz (amorphous SiO₂), porous Ni-YSZ and crystalline Alloy 600 (Fe-Ni-Cr) substrates using e-beam deposition technique and controlling technological parameters: substrate temperature and electron gun power which influence thin-film deposition mechanism. X-ray diffraction, scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to investigate how thin-film structure and surface morphology depend on these parameters. It was found that the crystallite size, roughness and growth mechanism of YSZ thin films are influenced by electron gun power. To clarify the experimental results, YSZ thin-film formation as well evolution of surface roughness at its initial growing stages were analyzed. The evolution of surface roughness could be explained by the processes of surface mobility of adatoms and coalescence of islands. The analysis of these experimental results explain that surface roughness dependence on substrate temperature and electron gun power non-monotonous which could result from diffusivity of adatoms and the amount of atomic clusters in the gas stream of evaporated material.     

Effect of electron beam on structural,linear and nonlinear properties of nanostructured Fluorine doped ZnO thin films

Electron beam induced effects on Fluorine doped ZnO thin films (FZO) grown by chemical spray pyrolysis deposition technique were studied. The samples were exposed to 8 MeV electron beam at different dose rate ranging from 1 kGy to 4 kGy. All films exhibit a polycrystalline nature which shows an increase in crystallanity with irradiation dosages. The electron beam irradiation effectively controls the films surface morphology and its linear optical characteristics. Z-Scan technique was employed to evaluate the sign and magnitude of nonlinear refractive index and nonlinear absorption coefficient using a continuous wave laser at 632.8 nm as light source. Enhancement in the third order nonlinear optical properties was were noted due to electron beam irradiation. Tailoring the physical and NLO properties by electron beam, the FZO thin films becomes a promising candidate for various optoelectronic applications such as phase change memory devices, optical pulse compression, optical switching and laser pulse narrowing.     

Effect of surface modification on dielectric and magnetic properties of metal powder/polymer nanocomposites

Metal nanopowder (Co and Fe)/polymer composites, both with and without surface modification by behenic acid, were fabricated and their dielectric and magnetic properties were measured at 1 GHz to study the effect of surface modification on the electromagnetic properties. The relative permittivity and the real part of the permeability of the composites with surface modified powders were higher than those with unmodified powders. Related dielectric losses remained at almost the same level, but magnetic losses were somewhat increased. The increase of relative permittivity could result from the increased volume fraction of interphase with a slightly higher relative permittivity at the particle/polymer interface than that of the bulk polymer. The increase in the real part of the permeability may be caused by suppression of the induced demagnetizing field due to suppression of eddy currents by a better particle distribution and a decrease in effective agglomerate size because of the surface modification.     

强流脉冲电子束辐照对NiCoCrAlY涂层结构和性能的影响

 采用低气压等离子体喷涂在DZ4镍基高温合金表面沉积NiCoCrAlY 涂层,并利用强流脉冲电子束（HCPEB）对其进行辐照处理。对HCPEB辐照处理前后的涂层的结构和性能分析得出,经HCPEB辐照处理后,疏松的涂层表面重熔,变得致密平整,产生微区光滑、熔坑和裂纹。X射线衍射分析表明,电子束辐照后涂层中的γ′相增多,涂层没有产生明显的残余微观内应力。900 ℃静态空气等温氧化试验结果显示,HCPEB辐照处理后,涂层的抗氧化性能明显提高。原因在于电子束辐照处理的涂层氧化后表面形成了更加完整的Al2O3保护层,同时γ′相的增加也有利于其耐氧化性能的提高。     

Correlation between structural and electrical properties of InN thin films prepared by molecular beam epitaxy

The strain-relaxation phenomena and the formation of a dislocation network in 2H-InN epilayers during molecular beam epitaxy are reported. The proposed growth model emphasizes the dominant role of the coalescence process in the formation of a dislocation network in 2H-InN. Edge type threading dislocations and dislocations of mixed character have been found to be the dominating defects in wurtzite InN layers. It is demonstrated that these dislocations are active suppliers of electrons and an exponential decay of their density with the thickness implies a corresponding decay in the carrier density. Room temperature mobility in excess of 1500 cm² V ⁻¹ s⁻¹ was obtained for 800 nm thick InN layers with dislocation densities of 3×10⁹ cm⁻².     

Cathodoluminescence properties of silicon nanocrystallites embedded in silicon oxide thin films

Cathodoluminescence (CL) spectra for the Si nanocrystallites embedded in a matrix of silicon oxide films are measured at room temperature. The CL spectra consist of two principal bands whose peak energies are in a near-infrared (NIR) region (<1.6 eV) and in a blue region (2.6 eV), respectively. The spectral feature of the NIR CL band is similar to the corresponding PL spectra. The strong correlation between the presence of Si nanocrystallites and the formation of the NIR CL band are found as well as the PL spectrum. The peak energy of the blue CL band is slightly lower than that of the luminescence band originating from oxygen vacancies (≡Si–Si≡) in SiO₂. Therefore, the blue CL band is considered to come from Si_n clusters with n3 in the oxide matrix. Under irradiation of electron beams, degradation of the intensity is observed for both the CL bands but the decay characteristics are different.     

Effect of thickness on physical properties of electron beam vacuum evaporated CdZnTe thin films for tandem solar cells

The thickness and physical properties of electron beam vacuum evaporated CdZnTe thin films have been optimized in the present work. The films of thickness 300 nm and 400 nm were deposited on ITO coated glass substrates and subjected to different characterization tools like X-ray diffraction (XRD), UV‐Vis spectrophotometer, source meter and scanning electron microscopy (SEM) to investigate the structural, optical, electrical and surface morphological properties respectively. The XRD results show that the as-deposited CdZnTe thin films have zinc blende cubic structure and polycrystalline in nature with preferred orientation (111). Different structural parameters are also evaluated and discussed. The optical study reveals that the optical transition is found to be direct and energy band gap is decreased for higher thickness. The transmittance is found to increase with thickness and red shift observed which is suitable for CdZnTe films as an absorber layer in tandem solar cells. The current-voltage characteristics of deposited films show linear behavior in both forward and reverse directions as well as the conductivity is increased for higher film thickness. The SEM studies show that the as-deposited CdZnTe thin films are found to be homogeneous, uniform, small circle-shaped grains and free from crystal defects. The experimental results confirm that the film thickness plays an important role to optimize the physical properties of CdZnTe thin films for tandem solar cell applications as an absorber layer.     

强流脉冲电子束辐照对NiCoCrAlY涂层结构和性能的影响

采用低气压等离子体喷涂在DZ4镍基高温合金表面沉积NiCoCrAlY 涂层,并利用强流脉冲电子束（HCPEB）对其进行辐照处理。对HCPEB辐照处理前后的涂层的结构和性能分析得出,经HCPEB辐照处理后,疏松的涂层表面重熔,变得致密平整,产生微区光滑、熔坑和裂纹。X射线衍射分析表明,电子束辐照后涂层中的γ′相增多,涂层没有产生明显的残余微观内应力。900 ℃静态空气等温氧化试验结果显示,HCPEB辐照处理后,涂层的抗氧化性能明显提高。原因在于电子束辐照处理的涂层氧化后表面形成了更加完整的Al2O3保护层,同时γ′相的增加也有利于其耐氧化性能的提高。     

Influences of oxygen partial pressure on structure and related properties of ZrO2 thin films prepared by electron beam evaporation deposition

ZrO₂ thin films were prepared by electron beam evaporation at different oxygen partial pressures. The influences of oxygen partial pressure on structure and related properties of ZrO₂ thin films were studied. Transmittance, thermal absorption, structure and residual stress of ZrO₂ thin films were measured by spectrophotometer, surface thermal lensing technique (STL), X-ray diffraction and optical interferometer, respectively. The results showed that the structure and related properties varied progressively with the increase of oxygen partial pressure. The refractive indices and the packing densities of the thin films decreased when the oxygen partial pressure increased. The tetragonal phase fraction in the thin films decreased gradually as oxygen partial pressure increased. The residual stress of film deposited at base pressure was high compressive stress, the value decreased with the increase of oxygen partial pressure, and the residual stress became tensile with the further increase of oxygen pressure, which was corresponding to the evolution of packing densities and variation of interplanar distances.     

非聚焦电子束照射SiO2薄膜带电效应

采用考虑电子散射、俘获、输运和自洽场的三维数值模型, 模拟了低能非聚焦电子束照射接地SiO₂薄膜的带电效应. 结果表明, 由于电子的迁移和扩散, 电子会渡越散射区域产生负空间电荷分布. 空间电荷呈现在散射区域内为正, 区域外为负的交替分布特性. 对于薄膜负带电, 电子会输运至导电衬底形成泄漏电流, 其暂态过程随泄漏电流的增加趋于平衡. 而正带电暂态过程随返回二次电子的增多而趋于平衡. 在平衡态时, 负带电表面电位随薄膜厚度、陷阱密度的增大而降低, 随电子迁移率、薄膜介电常数的增大而升高;而正带电表面电位受它们影响较小.     

UV light induced surface modification of HDPE films with bioactive compounds

The development of different techniques for surface modification of polymers becomes popular in a last decade. These techniques preserve useful bulk polymer properties unchanged, while the activation of the polymer surface offers more possibilities for polymer applications.In this work, a new, one-step method for bio-activation of HDPE (high density polyethylene) surface by UV irradiation is presented. HDPE films coupled with selected active compound and a photoinitiator was treated by UV lamp, emitting light at 254 nm.For surface functionalization of HDPE films, the following compounds were employed: 2-aminopyridine (AP), N¹-(2-pyridylaminomethyl)-1,2,4-triazole (TA) and benzocaine (BC). The influence of irradiation time on the extent of surface changes was investigated. The modified polymer surfaces were investigated by Fourier transformed infrared (FTIR) and Raman spectroscopy, scanning electron microscopy (SEM) and contact angle measurements, demonstrating successful functionalization of HDPE surface.