Microstructural Effects of Mn2+ ions in ZnO Nanoparticles

Semiconducting ZnO nanoparticles with manganese content 0 at. %, 5 at. % and 10 at. % were prepared by co‐precipitation technique and XRD reveals that the average crystallite size D is 10.2 nm, 7.62 nm and 7.06 nm respectively. The individual contributions of the size and strain to the XRD peak broadening were investigated by Williamson‐Hall (W‐H) analysis. The strain, stress and energy density were calculated more precisely by uniform deformation model (UDM), uniform stress deformation model (USDM), uniform deformation energy density model (UDEDM) and size‐strain plot (SSP) method. The average particle size from HRTEM analysis is 13 ± 2 nm. The evaluated average crystallite size from the W‐H analysis and SSP method is commensurate with the particle size from HRTEM. Diamagnetic to ferromagnetic phase transition observed is interpreted interms of the anisotropic strain due to the dopant.     

X-ray investigations of the defect structure of aluminium after plastic deformation

With plastic deformation of polycrystalline metals deformation textures are build up. Our experimental results show that the dislocation density increases, even with small plastic deformation. Simultaneously a decrease in the value of coherence length was revealed. The formation of a distinctly marked sub-structure, which is accompanied by an increase of the dislocation density, is essentially completed when plastic strain reaches 30 per cent. Further increase of the degree of deformation is followed by a change of orientation of the subgrains. When plastic strain is 60 per cent the deformation texture is almost completely accomplished.     

On the combined action of magnetic field and electric current on silicon plasticity

The specific features of the deformation behavior of low-resistivity p-type silicon single crystals have been studied using nontraditional methods of plastic deformation. Under the conditions of the combined action of a weak magnetic field and a direct electric current, a significant decrease in the plasticity of silicon is found during its active deformation when compared to the deformation in the absence of a magnetic field. An increase in the electrical conductivity of silicon samples subjected to active plastic deformation is found. The data that are obtained are compared with the previous data on single-crystal germanium. A possible explanation for the observed effects is given.     

Morphology and dispersion state of Ba2TiSi2O8 nanocrystals in transparent glass-ceramics and their nanoindentation behavior

The morphology and dispersion state of Ba₂TiSi₂O₈ (BTS) nanocrystals in transparent glass-ceramics (composition: 40BaO–20TiO₂–40SiO₂) were examined from high resolution transmission electron microscope observations, and their nano-scale deformation behavior was examined using Berkovich nanoindentation technique (standard-type and continuous stiffness measurement (CSM)-type). In the early stage of crystallization, BTS crystalline layers with a thickness of ~ 120 nm were formed at the surface and ellipsoid-shaped crystallites with a diameter of 100–200 nm were dispersed in the glass matrix. In the late stage, BTS crystals with a diameter of 200–400 nm were formed densely, but a glassy phase was present between BTS crystals. The Young's modulus evaluated from CSM-type nanoindentation measurements for a deformation scale of about 100 nm shows the values of 98 GPa for the glass and 110 GPa for the glass-ceramics with nanocrystals. It was suggested that CSM-type measurements are very sensitive in the nano-scaled homogeneity in the heat-treated samples.     

On the structure of thin plasma-treated thermal SiO2 films

Oxygen-plasma-treated thin thermal SiO₂ films (15–100 nm) have been studied by Reflection High Energy Electron Diffraction (RHEED). The presence of unconventional type microcrystalline regions (not only tetrahedrally coordinated) in the amorphous matrix of the oxides is established. Thinner oxides (15–50 nm) are more sensitive to the plasma action. In general, oxygen plasma leads to an additional deformation and decomposition of the initial crystalline forms and causes a degradation of the electrical parameters of the samples.     

X‐ray Diffraction Topography at a Synchrotron Radiation Source Applied to the Study of Bonded Silicon on Insulator Material

New possibilities of X‐ray diffraction topography offered by the modern synchrotron radiation sources for the investigation of wafer‐bonded material are demonstrated. They allowed detecting defects and long‐range strain fields at and close to the bonding interface. A quantitative estimation of the deformation of the region near to the bonding interface was possible e.g. by investigating focussing distances and dominant spatial frequencies of contrast patterns (often in the order of 200 μm). In typical wafer bonded material the maximum bonding‐induced inclination of the lattice planes was in the order of 10 arcsec and the approximate amplitude of the deformation in the order of 1.5 nm. The sensitivity of the presented methods to characterize the influence of various process parameters was demonstrated.     

Faraday Effect of BSO and BTO Crystals Doped with Cr,Mn and Cu

The influence of both photochromic doping and photochromic transitions on the effect of magneto‐optical rotation (Farady effect ‐ FE) of undoped and doped with Cr, Mn and Cu Bi₁₂SiO₂0 (BSO) and Bi₁₂TiO₂0 (BTO) crystals is studied. The present results show, that Cr, Mn and Cu increase the FE. The influence of Cr, whose affect on the optical activity (OA) of BSO is most significant, here is too negligible (Verdet coefficient (V) increases only with 1‐2 % in the range 700 ‐ 590 nm). The Mn‐doping of BSO led to a V‐increase with about of 11 % in the range 400 ‐ 700 nm, as at 460 nm the relative increase of V reaches to about 30 %. The influence of Cu on FE in BSO (likely the case of the natural optical rotation) is again significant. Thus, the influence of V in the case of BSO:Cu is about 18 % in the range 700 ‐ 480 nm as reaches 28 % in the shortwave region at 480 nm. However, in BTO:Cu (0.02 mol.% Cu) the influence of Cu is opposite in respect of both effects. Now the values of V increase with 21 % at 630 nm, 22 % at 590 nm, 42 % at 520 nm, and 73 % at 480 nm in comparison to BTO‐undoped.     

Competition of time and spatial scales in polymer glassy dynamics: Rejuvenation and confinement effects

We use molecular-dynamics (MD) simulations and an original lateral contact experiment to explore the influence of mechanical history on polymer mechanical behavior and segmental mobility. Two typical glassy polymers are considered: bulk acrylate (experiments) and atactic polystyrene (aPS) in a bulk and in thin films (simulations). Stress-strain behavior has been investigated both experimentally for sheared, 50 μm thick, acrylate films and by MD simulations of an aPS in a bulk for two different strain rates in a closed extension-recompression loops. Cyclic shear strains applied in the plastic regime were found experimentally to induce a progressive transition of the mechanical response of the polymer glass toward a steady state which is characterized by a strong reduction of the apparent - non linear - shear modulus. The dynamics of the polymer glass in this yielded state was subsequently analyzed from a measurement of the time dependent linear viscoelastic properties at various imposed frequencies. Immediately after the cyclic plastic deformation, mechanical “rejuvenation” of the polymer is evidenced by a drop in the storage modulus and an increase in the loss modulus, as compared to the initial values recorded before plastic deformation. A progressive recovery of the viscoelastic properties is also measured as a function of time as a result of the enhanced aging rate of the system. This experimentally observed mechanical rejuvenation of polymer has been for the first time connected to the drastic increase in the simulated segmental mobility. A simulated distribution of relaxation times shows a shift to shorter times of the α and β relaxation processes which is consistent with the observed experimental changes in the viscoelastic modulus after rejuvenation. Finally, we present our first findings on the thickness- and substrate-dependence of the simulated glass transition temperature for thin aPS films. We observe the decrease of the glass transition temperature with film thickness, but for extremely thin (less than 2 nm) films.     

Zn掺杂纳米TiO2材料制备与光催化性能的研究

通过水热合成的方法制备了Zn掺杂的纳米TiO2光催化剂.利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)及紫外-可见光分光计进行了物相结构、显微组织及光催化性能的检测与表征.结果表明:在Zn的掺杂量为0.6;时,纳米TiO2光催化剂由单一的锐钛矿相组成,晶粒尺寸约为6~10 nm,对太阳光的吸收波长增加到510 nm,提高对太阳光的利用效率,增强光催化的效果,经光催化反应100 min后,对甲基橙有机物的降解率达到92;.     

Correlated surface perturbation in stressed foil made of amorphous alloy

A foil strip made of amorphous alloy Fe₇₀Cr₁₅B₁₅ was loaded with the tensile stress ～500 MPa and remained with the ends kept fixed during 2 h. The statistical characterization of the temporal transformation of the sample surface relief was performed using the autocorrelation functions computed for one-dimensional profiles measured along the axis of loading. The profiles were recorded with the help of the scanning tunneling profilometer. The acquisition time of a single scan was about 0.5 min. The calculated autocorrelation function of the profile depths in the original foil shows a long-range (～2 × 10³ nm) correlation between relief components. The application of the tensile stress causes an immediate, significant increase of the roughness depth from ～40–50 nm to 100–200 nm with a corresponding drop of the correlation length to 0.7 × 10³ nm. The surface relief does not remain stable during loading but varies as a result of the competitive processes, such as microcrack growth, stress-induced flattening, and shearing. The variability of the deformation process in the ‘structureless’ amorphous alloy is due to the dynamical non-uniformity of the multi-focal damage nucleation.     

Crystal Data,Photoconductivity and Carrier Scattering Mechanisms in CuIn5S8 Single Crystals

The X‐ray diffraction has revealed that CuIn₅S₈ is a single phase crystal of cubic spinel structure. The value of the unit cell parameter for this crystal is 1.06736 nm. The crystal is assigned to the conventional space group Fd3m. The photocurrent is found to have the characteristic of monomolecular and bimolecular recombination at low and high illumination intensities, respectively. The electrical resistivity and Hall effect of CuIn₅S₈ crystals are measured in the temperature range of 50‐400 K. The crystals are found to be intrinsic and extrinsic above and below 300 K, respectively. An energy band gap of ∼1.35 eV at 0 K, a carrier effective mass of 0.2 m₀ , an acceptor to donor concentration ratio of 0.9, an acoustic phonon deformation potential of 10 eV and a nonpolar optical phonon deformation potential of 15 eV are identified from the resistivity and Hall measurements. The Hall mobility data are analyzed assuming the carrier scattering by polar optical phonons, acoustic combined with nonpolar optical phonons, and ionized impurities.     

影响化学机械抛光4H导电SiC晶片表面质量的关键参数研究

选用二氧化硅抛光液抛光4H导电SiC晶片表面,探究影响SiC晶片表面质量的关键参数,获得更高的去除效率和表面质量.实验结果表明,SiC表面的氧化是氢氧根离子和双氧水共同作用的结果.保持压力不变并增加氢氧根离子或双氧水的含量,SiC表面去除速率先增加后保持不变.在更大的压力下增加氢氧根离子的含量,SiC表面的抛光去除速率进一步增加.通过优化的抛光参数,SiC表面的抛光去除速率达到142 nm/h.进一步研究结果表明,保持化学机械抛光过程中氧化作用与机械作用相匹配,是获得高抛光效率和良好的表面质量的关键.表面缺陷检测仪(Candela)和原子力显微镜(AFM)的测试结果表明,SiC抛光片表面无划痕,粗糙度达到0.06 nm.外延后总缺陷密度小于1个/cm2,粗糙度达到0.16 nm.     

Low-temperature anomalies in the plastic response of crystalline materials

The non-uniform, wavy, temperature-dependence of the yield-stress and of the rate of logarithmic creep frequently observed in metals, alloys and non-metallic crystalline solids at low temperature, is shown to be largely a consequence of the progressive inhibition of dynamic recovery processes as T → 0 K. Plastic deformation becomes increasingly localised, resulting in high stress-concentrations. On allowing for this increase in the usual equations of the deformation kineties, the anomalies are very well accounted for.     

Eu3+离子注入β-Ga2O3单晶的应力变化和发光性质研究

采用离子注入法制备了不同剂量的β-Ga₂O₃:Eu³⁺样品,并在空气中进行了退火处理,成功实现了Eu³⁺的光学激活。通过拉曼和X射线衍射表征了β-Ga₂O₃晶体随Eu³⁺注入剂量的应力变化趋势,发现随着Eu³⁺剂量的增加,晶格应力先增加后减少,并对其内在机理进行了分析。利用阴极荧光光谱对晶体的发光性质进行了表征,主要观察到峰值位于380 nm附近、宽的缺陷发光峰以及峰值位于591 nm、597 nm和613 nm的Eu³⁺发光峰。通过高斯拟合发现,该380 nm发光峰主要由360 nm、398 nm和442 nm三个子峰构成,分别与自陷激子和施主-受主对有关。此外,Eu³⁺发光峰位置与强度受到基质局域晶体场的影响。     

耐高温氧化锆-刚玉-莫来石复相陶瓷的制备及其抗热震性

以煤系高岭土、α-Al2O3和部分稳定氧化锆(PSZ, 3;molY2O3)为原料,制备了耐高温氧化锆-刚玉-莫来石复相陶瓷.采用XRD、SEM等测试技术对样品的物相组成及显微结构进行了表征,研究了PSZ添加量(分别为5wt;、10wt;、15wt;、20wt;、25wt;、30wt;)对样品物理性能、高温塑性变形及抗热震性的影响.结果表明:由于采用含3;molY2O3的PSZ,Y2O3在高温下起到了烧结助剂的作用,致使样品的烧成温度显著降低;同时随着PSZ添加量的增加,样品的抗折强度增加.经最佳烧成温度烧成的各样品的抗折强度分别达到147.4 MPa、161.3 MPa、205.9 MPa、234.4 MPa、294.0 MPa、385.0 MPa.当PSZ的最佳添加量为10wt;时,样品具有较低的高温塑性变形及良好的抗热震性;当PSZ添加量继续增加,样品在高温易产生液相,抗蠕变及抗热震性降低.SEM显微结构研究表明,随着氧化锆添加量增加,样品结构越致密,增强效果越显著.XRD分析结果表明,复相陶瓷具有良好的耐高温性能,热震前后样品的物相组成不变,均为莫来石、刚玉、m-ZrO2和t-ZrO2.     

Electrical and corrosion properties of the Ti5Si3 thin films coated on glass substrate by APCVD method

Ti₅Si₃ thin films were coated on glass substrate by atmospheric pressure chemical vapor deposition method at different temperatures. Electrical and corrosion properties of the thin films were investigated. The results show that the electrical resistivity of the thin films decreases initially with the increase in deposition temperature. However, it increases with the further increase of the temperature. The lowest electrical resistivity of 107 μΩ⋅cm is obtained at 710 °C. The least corrosion rates of the thin films at 95 °C of 0.10 nm/min and 0.13 nm/min in 1 N and 10 N acid solution and of 0.33 nm/min and 6.55 nm/min in 1 N and 10 N alkali solution, respectively, are obtained by weight-loss measurement method. The corrosion mechanisms of the thin films were also discussed in detail.     

溶胶-凝胶法制备紫外及蓝光双截止润眼镀膜玻璃

采用溶胶-凝胶法,在3 mm厚的普白玻璃含锡面镀制镶嵌Ag纳米粒子的氧化硅薄膜,达到吸收蓝光的效果,在其非锡面镀制纤锌矿结构的氧化锌薄膜,达到阻隔紫外效果.通过双膜层的相互作用,达到对紫外和短波蓝光有效阻隔吸收,从而获得具有紫外蓝光防护及润眼功能的镀膜玻璃.研究了热处理温度和膜层厚度对近紫外和蓝光阻隔率的影响.结果表明:随着退火温度的升高,膜层更加致密,且退火温度越高,蓝光的吸收率也逐渐提高,吸收峰位红移.利用浮法玻璃本体的富锡表面还原AgNO3成Ag纳米粒子分散镶嵌在氧化硅薄膜的结构,能有效吸收380～450 nm的短波蓝光.实验样品呈现出美观的淡金黄色,且随着膜厚的增大,金黄色程度逐渐加深.以样品a为例,所制备的氧化锌膜层为稳定的纤锌矿结构,膜厚为438 nm,表面为球状颗粒,对380 nm以下的紫外光阻隔率为98.83;;所制备氧化硅薄膜厚为200 nm,表面致密,对380～450 nm的蓝光阻隔率为90.73;,样品整体450～780 nm可见光透过率为77.8;.     

Study on Ag doping in congruent lithium niobate crystal

Ag doped congruent lithium niobate crystal has been demonstrated as a promising photorefractive material for holographic recording applications. In this paper, the effects of Ag doping on the lattice structure and the optical properties were investigated by XRD, Raman spectroscopy and optical absorption characterization. The Ag ion was proposed to occupy Li-sites and results in lattice deformation. The band gap became narrower and an absorption band at near 500 nm was created with Ag doping. High temperature annealing and UV irradiation were performed to further understand the Ag doping effects.     

Electromagnetic emission under uniaxial compression of ice: III. Dynamics and statistics of dislocation avalanches and cracks

Statistical analysis of the plastic deformation steps and fracture of polycrystalline ice has been performed. It is established that an increase in deformation leads to gradual evolution of the statistics of amplitudes of mesoscopic deformation jumps from random (with a Poisson distribution of dislocation avalanche amplitudes) to “critical” (with a power-law distribution), which indicates occurrence of long-range correlations of the dislocation mesodynamics of deformed polycrystalline ice. The state of self-organized criticality at subcritical ice fracture has been revealed from the power-law statistics of the amplitudes of electric pulses and pauses between them, flicker-noise structure, and almost monofractal character of signals.     

Structural,optical and photoluminescence properties of ZnS: Cu nanoparticle thin films as a function of dopant concentration and quantum confinement effect

Thin films of ZnS: Cu nanoparticles were deposited in chemical bath by a pH controlled solution synthesis technique. The copper concentration was varied from 0 to 0.1M%. XRD and SEM indicated variations in diffracted intensity and morphology with Cu concentration. The PL spectrum of the undoped ZnS nanoparticles showed emission peaks at 393 and 432nm that could be attributed to the intrinsic defect states of ZnS nanoparticles. For ZnS: Cu samples three peaks in the range of 390nm, 480nm and 525nm were observed. With increase in Cu concentration from 0.001 to 0.1M%, the peak position of 480nm and 525nm did not change, whereas 390nm peak red shifted to longer wavelength region to 422nm. In addition, it was found that the overall photoluminescence intensity reached maximum at 0.01M% and quenched with further increase in Cu concentration. Enhancement of blue and green light emission by seven and twenty fivefold respectively compared to undoped ZnS was observed in ZnS: Cu with optimal dopant concentration. Time resolved decay of photoluminescence showed faster decay for 390 – 420nm purple/ blue emission compared to green (525nm) Cu related emission which is in the microsecond time scale. Optical absorption measurements indicate enhancement of band gap (3.89eV) for undoped ZnS suggesting the quantum confinement effect in the developed nanoparticles of size below the Bohr diameter. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)