Texture, residual stress and structural analysis of thin films using a combined X-ray analysis

Advanced thin films for today's industrial and research needs require highly specialized methodologies for a successful quantitative characterization. In particular, in the case of multilayer and/or unknown phases a global approach is necessary to obtain some or all the required information. A full approach has been developed integrating novel texture and residual stress methodologies with the Rietveld method (Acta Cryst. 22 (1967) 151) (for crystal structure analysis) and it has been coupled with the reflectivity analysis. The complete analysis can be done at once and offers several benefits: the thicknesses obtained from reflectivity can be used to correct the diffraction spectra, the phase analysis help to identify the layers and to determine the electron density profile for reflectivity; quantitative texture is needed for quantitative phase and residual stress analyses; crystal structure determination benefits of the previous. To achieve this result, it was necessary to develop some new methods, especially for texture and residual stresses. So it was possible to integrate them in the Rietveld, full profile fitting of the patterns. The measurement of these spectra required a special reflectometer/diffractometer that combines a thin parallel beam (for reflectivity) and a texture/stress goniometer with a curved large position sensitive detector. This new diffraction/reflectivity X-ray machine has been used to test the combined approach. Several spectra and the reflectivity patterns have been collected at different tilting angles and processed at once by the special software incorporating the aforementioned methodologies. Some analysis examples will be given to show the possibilities offered by the method.     

利用临界角附近光能量的变化测量溶液浓度

讨论了在临界角附近入射到介质表面时光能量变化的基本规律和在不同情况下反射光能量与溶液浓度的关系，给出了测量浓度的实验方法，测量数据表明，反射方法测量浓度是可行的，具有良好的应用前景。     

碳纤维复合吸波涂层材料的性能影响研究

以水性聚氨酯为基,碳纤维为填料,制备了碳纤维复合吸波涂层材料。采用扫描电镜、差示扫描量热仪、傅里叶红外光谱仪、X射线衍射仪和矢量网络分析仪对碳纤维复合吸波涂层材料的结构与性能进行了测试和表征。实验结果表明:碳纤维复合吸波涂层材料为碳纤维和水性聚氨酯的物理结合,随着碳纤维含量的增加和厚度的增大,碳纤维复合吸波涂层材料的反射率峰值均向低频移动,当碳纤维含量为0.8%,涂层厚度为1.2 mm时,碳纤维复合吸波涂层的反射率峰值达到-6.01 dB,小于-5 dB的带宽为4.2 GHz,涂层面密度为1.02kg/m~2。     

Effect of the etching time on the morphological, optical and electronic properties of silicon nanowires

ABSTRACT: Owing to their interesting electronic, mechanical, optical and transport properties, silicon nanowires (SiNWs) have attracted much attention, giving opportunities to several potential applications in nanoscale electronic, optoelectronic devices and silicon solar cells. For photovoltaic (PV) application, a superficial film of SiNWs could be used as an efficient antireflection coating (ARC). In this work, we investigate the morphological, optical and electronic properties of SiNWs fabricated at different etching time. Characterizations of the formed SiNWs films were performed using a Scanning Electron Microscope (SEM), UV-Vis-NIR spectrophotometer and Light-Beam-Induced-Current (LBIC) technique. The later technique was used to determine the effective diffusion length in SiNWs films. From LBIC investigations, we deduce that the homogeneity of the SiNWs film play a key role on the electronic properties.     

新型隔热降温涂料的研制

介绍了新型隔热降温复合涂层的工作原理,确定了复合涂层的组成和成分,考察了复合涂层的隔热降温效果。     

Design and preparation of composite coatings with increased reflectivity under high-energy continuous wave laser ablation

High-energy continuous wave (CW) laser ablation can cause severe damage to structural materials in an extremely short time, which generates considerable concern in terms of material safety. For the purpose of reducing or even eliminating such laser-induced damage, a novel composite coating consisting of a boron-modified phenolic formaldehyde resin incorporating ZrC and SiC has been designed and prepared. The experimental results reveal that ZrC and SiC are rapidly oxidized to ZrO₂ and SiO₂ respectively, leading to the formation of a white ceramic layer consisting of ZrO₂ particles and melted SiO₂. After ablation at 1000 W/cm² for 50 s, elemental analysis indicates that no Si can be found in the central ablation zone because of gasification. A relatively compact ZrO₂ layer is formed through the sintering of adjacent ZrO₂ particles, which effectively improves the reflectivity of the coating from 7.3% (before ablation) to 63.5% (after ablation). The high reflectivity greatly reduces the absorption of laser energy. In addition, no obvious ablation defects are observed in the composite coating. The excellent anti-laser ablation performance of the coating makes it a promising system for protecting a material against the effects of long-term CW laser ablation.     

Control of Hole Concentration in Liquid-Phase Epitaxial Layers of PbTe by As Doping

Liquid-phase epitaxial layers of PbTe grown at ⋍55O‡C have been doped p-type over the concentration range 5 × 10¹⁶ − 5 × 10¹⁸cm^-3by adding from 0.004 − 10 at.% arsenic to the melts. The hole concentrations of the layers, which were grown on p+ substrates, were obtained from plasma reflectivity and thermoelectric probe measurements. The latter assessment technique is shown to be a reliable and simple method for determining the hole concentration in epitaxial layers with thicknesses greater than ≃ 5ym, provided the damage introduced by the probe is controlled. Damage can cause negative thermoelectric power signals to be obtained from p-type PbTe, showing that dislocations introduce donor centres in this material.     

Optical properties of β-FeSi2 single crystals grown from solutions

We studied the optical absorption, polarized reflectance (PR) and photoluminescence (PL) of β-FeSi₂ single crystals grown from solution. In low-absorption measurements, we found a phonon emission and absorption structure, which suggests an indirect transition. The exciton energy gap of 0.814 eV was determined from the absorption spectrum at 3.5 K. We also found a direct transition with the gap energy of 0.939 eV. PR measurements for Ea, Eb and Ec revealed the anisotropy of reflectivity of β-FeSi₂. We observed the PL with a peak wavelength of about 1.56 μm at 20 K.     

基于高光谱的土壤重金属铜的反演研究

为探讨高光谱遥感反演红壤重金属铜含量的可行性,研究采集了34个红壤性土壤样品,通过对350~2 500 nm波段范围光谱曲线进行测试和分析,建立了不同的土壤光谱变量与重金属铜含量多元回归关系模型,分析了土壤重金属铜与土壤化学组分以及土壤特征光谱的关系。结果表明,土壤重金属铜含量与土壤全铁和镁含量显著相关,而与土壤有机质的相关性不显著,表明红壤性土壤粘土矿物对土壤铜含量影响较大;与重金属铜含量相关性较好的波段在830 nm、1 000 nm和2 250 nm附近,且一阶微分模型精度(79%)高于反射率模型(66.26%)和倒数对数模型(67%)的精度。因此,一阶微分高光谱反演模型具有较好的快速估算土壤中重金属铜含量的潜力。     

On the characterization of Al-0.11 wt.%Sc alloy thin film

The characterizations (i.e., film adhesion, optical reflectivity, illumination aging and anti-corrosion behavior) should be considered for the metallic thin film served as a candidate of autolamp materials. The characterizations of three candidates (i.e., sputtered Al-0.11 wt.% Sc, sputtered pure Al, and thermally evaporated pure Al) have been investigated and compared. The sputtered Al-0.11 wt.% Sc film performed much better than any of the other two regarding the characterizations concerned. Examining through AFM, the sputtered Al-0.11 wt.% Sc revealed better surface property (including flatness and smoothness) than the others. Excellence in surface properties and optical reflectivity for the Al-0.11 wt.% Sc may arise from grain refinement in the film. Under long-term illumination, the films led to grain growth and hillocks formation. This illumination aging degraded the surface properties and optical reflectivity of the films, especially for the pure Al films. The sputtered Al-0.11wt.%Sc revealed more corrosion-resistance than the other films in 5% NaCl solution regardless whether or not under illumination aging.