Periodic Mo/Si/C multilayers were fabricated on inclined substrates using magnetron sputtering deposition, either without applying a substrate bias voltage or with various bias voltages applied. Their surface and interface roughness, surface power spectral densities, multilayer structures, grazing-incidence X-ray reflectivity, and extreme ultraviolet reflectivity (EUVR) were characterized. The layer thickness and density were determined by fitting the reflectance spectrum. Overall, the multilayers deposited under a substrate bias voltage demonstrated lower surface and interface roughness and higher layer density, both of which contributed positively to the EUVR. However, applying a substrate bias voltage also increased interface diffusion, particularly at bias voltages exceeding -50 V, which adversely affected the EUVR. By selecting an appropriate substrate bias voltage, the formation of ripples in multilayers deposited on inclined substrates can be mitigated, resulting in reduced surface and interface roughness, increased layer density, and ultimately higher EUVR. A reflectivity of 67.2 % was achieved on a substrate with an inclination angle of 39 degrees using a 60-period Mo/Si/C multilayer structure.

Freestanding Zr filters are important devices for improving spectral purity in the extreme ultraviolet range of 7-20 nm, and their irradiation resistance directly determines their life and efficiency. We prepared multilayered Zr/B4C and Zr/Si filters using magnetron sputtering. Their transmittance reached a maximum of 23% (lambda =13.5 nm). Microwatt-radiation-induced structural changes in the filters were investigated at the metrology beamline (BL08B) of the National Synchrotron Radiation Laboratory. The aging of the Zr filters was measured and analyzed. The experimental results revealed that the damage was noticeable on the irradiated filter surfaces with different states, suggesting that the main factors causing the degradation of the filters were oxidation and carbon contamination at the surfaces. Furthermore, the thermal stability of the Zr filters was studied by annealing, and the heat accumulation during the damage process was estimated using finite-element numerical simulations and X-ray photoelectron spectroscopy measurements. Silicide formation at the Zr-Si-O system interfaces was found to be key to enhancing the stability of the filters.

Objective Mo/Si multilayer films exhibit the highest measured reflectivity in the extreme ultraviolet (EUV) region, and their combination with an EUV light source enables EUV lithography. In practical applications of EUV light sources, Mo/Si multilayer mirrors are always curved and have large diameters. The angle of the incident light constantly changes along the curved surface. To match the multilayer peak reflectivity with the angle of the incident light, the period thickness of the Mo/Si multilayer films must be distributed in a transverse gradient along the surface to ensure high EUV reflectivity. Simultaneously, given that the mirror is close to the light source, the multilayer films must operate in an environment with a high thermal load. Higher temperatures can increase the formation of silicide at the multilayer interface, causing the optical performance to decrease. Therefore, Mo/Si multilayer films for EUV light sources also have high thermal stability requirements. To address these issues, we use a shadow mask to correct the periodic thicknesses of the multilayer films at different positions on a curved substrate with a diameter of 300 mm. Carbon is selected as the diffusion barrier material to investigate the influence of C-barrier layer on the thermal stability of Mo/Si multilayer. Methods In this study, two sets of Mo/Si multilayer films are deposited via direct current(DC) magnetron sputtering onto super-polished silicon wafers, and the thickness control and thermal stability of the Mo/Si multilayer films are investigated separately. For the study of thickness control, the target period thickness is from 6.96 nm to 7.31 nm, and the ratio of Mo layer thickness to period thickness is approximately 0.40. As the multilayer thickness on a large curved substrate cannot be measured directly, we prepare a substituted substrate to estimate the multilayer thickness at selected points on the surface. The shadow mask technique is used to adjust the periodic thickness of the multilayer films at different positions on the entire mirror. C is selected as the barrier material for the thermal stability study. Mo/Si, Mo/Si/C, and Mo/C/Si/C multilayer films are annealed at 300 degrees C for 2 h. By observing the X-ray reflectivity (XRR) and EUV reflectivity before and after annealing, the effect of the C barrier layer on the thermal stability of Mo/Si multilayer films is investigated. Results and Discussions In the study involving film thickness control, the XRR measurement results show that the samples at different positions exhibit similar layer structures (Fig.4). Atom force microscope (AFM) tests are performed on Mo/Si multilayer films deposited at four different positions on the entire mirror. The surface roughness values of the four samples are 0.128,0.123,0.124, and 0.118 nm. The morphologies of the four samples are similar (Fig.5). Using the shadow mask, the deviation of the period thickness on the 300-mm diameter curved substrate is controlled within +/- 0.45% of the expected period thickness (Fig.6).In the study involving thermal stability, after annealing at 300 degrees C for 2h, the period thickness of Mo/Si multilayer films changes from 6.99 nm to 6.69 nm, the period thickness of Mo/Si/C multilayer films changes from 6.96 nm to 6.91 nm, and the period thickness of Mo/C/Si/C multilayer films is almost same before and after the annealing, which changes from 6.97 nm to 7.00 nm. The C barrier layer can effectively mitigate the interdiffusion at the interface of the Mo and Si layers, which improves the thermal stability of the multilayer films (Fig.7). The EUV reflectivity of Mo/Si multilayer films decreases from 64.4% to 55.4% after annealing at 300 degrees C for 2 h, and the central wavelength has a shift of 0.51 nm. The EUV reflectivity of the Mo/Si/C multilayer films decreases from 66.4% to 59.6% after annealing, and the center wavelength shifts by 0.11 nm. The reflectivity of Mo/C/Si/C multilayer films decreases by 1.8% after annealing, and central wavelength shifts by 0.02 nm (Fig.8 and Table 2). Furthermore, the EUV reflectivity results show that the C barrier inserted at both interfaces of the Mo/Si multilayer films can significantly improve thermal stability. Conclusions Initially, graded Mo/Si multilayer films are deposited on a large-diameter curved substrate using a shadow mask.Compared with the designed period thickness, the deviation in the period thickness at different positions on the entire substrate is controlled within +/- 0.45%. The layer structure and surface roughness of the Mo/Si multilayer films are almost identical at different positions. This study provides useful guidance for the fabrication of large curved multilayer mirrors for EUV light sources. Next, the thermal stability of the Mo/Si multilayer films is investigated after inserting a C-barrier layer. The results show that the thermal stability of the Mo/C/Si/C multilayer films is optimal, and that of the Mo/Si multilayer films is the worst. The Mo/C/Si/C multilayer films exhibit only 1.8% reflectivity loss after annealing at 300 degrees C for 2 h, and the center wavelength and bandwidth do not change. The higher reflectivity and multistability of Mo/Si multilayer films for EUV sources are currently under investigation

Multilayers (MLs) are a good choice for high-harmonic generation (HHG) sources for selecting single-wavelength radiation. MLs working around 30.4 nm with a significantly reduced bandwidth based on high Bragg order reflection have been designed and fabricated. The narrowband MLs were characterized using grazing incidence x-ray reflectometry, extreme ultraviolet reflectivity, and intrinsic stress measurements. The results indicate that Mg/SiC MLs designed with 3rd Bragg order have narrowest bandwidth of 0.71 nm (full width half maximum) with a spectral resolution (lambda/Delta lambda) of 42, and reflectance of 30% under near normal incidence geometry. Based on these results, the simulation of narrowband MLs working at large incident angles demonstrates that 3rd Bragg order ML has a better spectral selectivity compared with 1st Bragg order ML for HHG sources.

Mirror stability is crucial for their applications, especially in the far ultraviolet (FUV) where Al mirrors protected with fluoride are the preferred choice. This study evaluates the effect of storage conditions on the performance of Al/LiF/MgF2 mirrors and compares them with previous investigations of Al/LiF/eMgF(2) mirrors. This study focuses on FUV reflectivity, structural characteristics, and the long-term stability of mirrors stored in various environments. Coatings were deposited on the super-polished silicon wafers using thermal evaporation. Three sets of mirrors were stored in the environment with 20% relative humidity (RH), 40% RH, and 80% RH, respectively. Additionally, three other sets were stored in vacuum, nitrogen (N-2), and oxygen (O-2), respectively, in sealed bags kept in a 40% RH environment. Mirrors stored in a 20% RH environment demonstrated the best performance, exhibiting the smallest decline in reflectivity and a relatively stable surface morphology. Conversely, mirrors stored in 80% RH experienced a significant reduction in reflectivity, accompanied by the most pronounced deterioration in surface morphology. It was concluded that the chemical changes and high roughness of the films contributed to the decrease in the reflectivity.

The Mo/Si multilayer mirror has been widely used in EUV astronomy, lithography, microscopy and other fields because of its high reflectivity at the wavelength around 13.5 nm. During the fabrication of Mo/Si multilayers on large, curved mirrors, shadow mask was a common method to precisely control the period thickness distribution. To investigate the effect of shadow mask on the microstructure of Mo/Si multilayers, we deposited a set of Mo/Si multilayers with and without the shadow mask on a curved substrate with aperture of 200 mm by direct current (DC) magnetron sputtering in this work. Grazing incidence X-ray reflectivity (GIXR), diffuse scattering, atomic force microscope (AFM) and X-ray diffraction (XRD) were used to characterize the multilayer structure and the EUV reflectivity were measured at the National Synchrotron Radiation Laboratory (NSRL) in China. By comparing the results, we found that the layer microstructure including interface width, surface roughness, layer crystallization and the reflectivity were barely affected by the mask and a high accuracy of the layer thickness gradient can be achieved.

To investigate the thermal stability of Mo/Si multilayers with different initial crystallinities of Mo layers, two kinds of Mo/Si multilayers were deposited by DC magnetron sputtering and annealed at 300°C and 400°C. The period thickness compactions of multilayers with crystalized and quasi-amorphous Mo layers were 0.15 nm and 0.30 nm at 300°C, respectively, and the stronger the crystallinity, the lower the extreme ultraviolet reflectivity loss. At 400°C, the period thickness compactions of multilayers with crystalized and quasi-amorphous Mo layers were 1.25 nm and 1.04 nm, respectively. It was shown that multilayers with a crystalized Mo layer had better thermal stability at 300°C but were less stable at 400°C than multilayers with a quasi-amorphous Mo layer. These changes in stability at 300°C and 400°C were due to the significant transition of the crystalline structure. The transition of the crystal structure leads to increased surface roughness, more interdiffusion, and compound formation.

A laboratory-based reflectometer designed for characterizing the reflectivity of optical coatings in 30- to 200-nm wavelength range was recently developed at IPOE. An RF-produced gas-discharge light source is applied to generate characteristic lines. The light source is mounted on a grazing incident monochromator with a 146-deg deviation angle between the incident and diffracted arms. By precisely adjusting the toroidal grating inside the monochromator chamber, monochromatic lights are acquired through the exit slit. A collimator mirror and two sets of collimation slits with 2 mm x 2 mm dimension are utilized for reducing the divergence of the beam incident on the sample. A high-precision six-axis translation stage, which allows a heavy sample with a maximum diameter of 100 mm, is used to control positions of the samples and the detector. A chopper disk used both for incident light intensity monitor and signal modulation is placed with an incidence angle of 70 deg relative to the incident light beam. The configuration, adjustment process, and test results of the reflectometer are presented in detail. The experimental reflectivity results for Al/LiF/MgF2 film obtained from our laboratory and BESSY-II Synchrotron as well as Hefei Synchrotron Light Source are given and compared for demonstrating the reliability of the system. (C) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 International License.

Quasi-periodic nanostructures induced by ion bombardment (IB) on solid surfaces are characterized by small periods (10-100 nm) and large areas. Quasi-periodic nanoripple structures with the transverse feature size of around 100 nm and the gradually significant transverse periodicity and longitudinal continuity were fabricated on antireflection coatings by Argon-IB. To improve the characterization area, the morphological characteristics of the self-organized nanoripples were characterized by using extreme ultraviolet (EUV) scatterometry. The results show that in terms of samples, their transverse and longitudinal morphological features obtained by the in-plane and conical mode of the EUV scatterometry are in agreement with those obtained by atomic force microscope. These results demonstrate that the proposed method is feasible to characterize the basic morphological characteristics of quasi-periodic nanoripples and can provide a basis for subsequent quantitative analysis. In addition, the characterization area of self-organized nanoripple structures has reached an order of the mm(2) by EUV synchrotron radiation, and the characterization range of the Metrology Beamline of Hefei Light Source is extended to self-organized nanostructures, which can provide a reference for future studies on the scattering characterization of EUV lithography masks.

散焦模糊检测存在轮廓细节丢失、错分均质清晰区域以及难以处理低对照度渐变区域等诸多问题,针对上述问题,提出一种基于双向互补学习的散焦模糊检测网络,双向学习、逐层融合、互补信息以生成高质量检测结果.双向互补学习网络由特征提取残差模块、双向互补解码子网和融合校正解码子网构成.残差模块提取原始图像的分层级特征;双向互补解码子网同时学习模糊区域和清晰区域的信息,形成互补学习、互补不足;融合校正解码子网则逐层融合成对互补特征图,校正预测误差;此外,所有解码子网均采用分层监督的方式引导网络高效学习.提出的方法在三个公开数据集上F分数分别提升了1.1％、0.1％、1.8％,检测速度达到26.618 fps,超越了现存方法.双向互补学习网络可以有效地挖掘分层级特征和互补标签的信息,快速地生成检测结果.

The far ultraviolet (FUV) spectrum is critical for the observation of phenomena in space, among various other applications. Hence, the aim of our study was to investigate the effect of the humidity of Al mirrors coated with LiF and enhanced MgF2 within the FUV spectrum. The samples were first coated with Al and LiF films on a super-polished silicon wafer at room temperature, heated to 220 degrees C, and then coated with an enhanced MgF2 film. All materials were deposited by thermal evaporation. The samples were stored in environments with 20% relative humidity (RH), 40% RH, 80% RH, and 90% RH. The reflectivity remained stable when the environment was 20% RH, which was the optimal storage environment. The reflectivity of the Al / LiF / eMgF(2) mirrors stored in high RH decreased over time, the roughness increased over time. Furthermore, the decrease rate of reflectivity and increase rate of roughness decreased over time. The degradation of reflectivity can be attributed to the presence of oxygen in environments with a high RH. (c) 2021 Society of Photo-Optical Instrumentation Engineers (SPIE)

To increase efficiency of single layer gratings used in the tender x-ray range, a high reflectance multilayer can be directly grown on single layer gratings. Multilayer growth quality was studied by depositing the Cr/C multilayer on a Pt single layer using flat substrates. Their structure quality and adhesion were characterized by atomic force microscopy (AFM), grazing incidence x-ray reflectivity (GIXRR), x-ray scattering (XRS), x-ray diffraction (XRD), and layer adhesion measurement. AFM results showed that the surface roughness was 0.218 nm for the multilayer without the Pt layer and 0.272 nm for the multilayer with the Pt layer. As GIXRR results showed, the average interface widths were 0.39 nm for the multilayer without the Pt layer and 0.42 nm for the multilayer with the Pt layer. XRS results indicated that the existence of a Pt layer enlarged slightly the roughness of the multilayer. Simulation results exhibited that these slight changes caused by the Pt layer had an insignificant effect on reflectivity. As XRD results displayed, the crystallization of the Pt layer had negligible effects on the crystallization of Cr in films. The layer adhesion measurement revealed that the critical loads to peel off the layer from the substrate were 84.64 mN for the multilayer without the Pt layer and 33.99 mN for the multilayer with the Pt layer. After 6 months, the latter layer structure is undamaged, demonstrating that the coating is not easily peeled off. This study proves the feasibility to upgrade a low efficiency single Pt layer grating to a highly efficient multilayer grating.

为满足虚拟手术中软组织变形的精确性和实时性要求,提出一种基于复合模型的软组织变形模拟算法.该复合变形模型包括复合网格的建立,复合网格中粗糙体网格应用有限元模型,精细表面网格应用基于位置动力学模型,通过变形计算流程实现变形模拟.复合模型与传统的有限元模型和基于位置的动力学模型相比,变形的精确性和实时性取得了更好的平衡.通过变形实例,表明复合模型对于实例模型也具有很好的展示效果.

The existing matching algorithm has a low registration accuracy of point clouds with low overlap, and is more sensitive to different scales. In order to achieve a better registration effect, it is necessary to preprocess or adjust more parameters to the point cloud. Fast point feature histogram (FPFH) has a low complexity, and retains most of the features of the point cloud. Therefore, we propose an improved registration algorithm based on FPFH of the point cloud. First, extracting key points with multi-scale features based on FPFH to adapt to different scales point cloud datasets, while reducing the number of parameters that require adjustment. Then, the corresponding point relationship after the initial screening of FPFH matching is accurately extracted, the distance constraint condition in the point cloud is added, which reduces sensitivity of the algorithm to overlap and the preliminary transformation matrix of registration is obtained. Finally, the iterative closest point algorithm is subjected to finetuning to achieve the purpose of accurate registration. The experimental results show that the algorithm has good registration accuracy on different overlap and different scales of point cloud datasets.

In some simulations like virtual surgery, an accurate surface deformation method is needed. Many deformation methods focus on the whole model swing and twist. Few methods focus on surface deformation. For the surface deformation method, two necessary characteristics are needed: the accuracy and real-time performance. Some traditional methods, such as position-based dynamics (PBD) and mass-spring method (MSM), focus more on the real-time performance. Others like the finite element method (FEM) focus more on the accuracy. To balance these two characteristics, we propose a hybrid mesh deformation method for accurate surface deformation based on FEM and PBD. Firstly, we construct a hybrid mesh, which is composed of a coarse volume mesh and a fine surface mesh. Secondly, we implement FEM on coarse volume mesh and PBD on fine surface mesh, and the deformation of fine surface mesh is constrained by the displacement of the coarse volume mesh. Thirdly, we introduced a small incision process for our proposed method. Finally, we implemented our method on a simple deformation simulation and a small incision simulation. The result shows an accurate surface deformation performance by implementing our method. The incision effect shows the compatibility of our proposed method. In conclusion, our proposed method acquires a better trade-off between accuracy and real-time performance.

多层膜反射镜是X射线波段和极紫外波段的重要光学部件.碳化硼作为常见的反射膜材料,其薄膜成分及光学常数计算的准确性对反射镜的反射性能具有明显影响.本研究使用直流磁控溅射技术制备碳化硼薄膜,利用X射线光电子能谱(XPS)、X射线全反射(XRR)、原子力显微镜(AFM)和同步辐射光源等对试样进行了表征,利用改进的拟合函数拟合了基底和薄膜的反射率曲线.结果表明,非晶碳化硼薄膜的元素化学状态相同,其基本成分包含碳化硼和含氧碳化硼;在5～45 nm波段,薄膜B/C摩尔比为4.23时,反射性能最好,同时其基底与薄膜的电子密度差值最大,试样反射性能变化与试样电子密度差值变化基本一致;与原始拟合函数相比,改进的拟合函数提高了薄膜光学常数计算的准确性.

Image synthesis and super-resolution (SR) have always been a hot spot for computer vision and image processing research. Since the development of Deep Learning, especially after the Deep Convolutional Generative Adversarial Network (DC-GAN) methods, facial image synthesis and SR problem had been solved in many circumstances. But most of the existing works were focused on natural-looking of the synthesized result rather than keeping facial information of the original image. Our paper presented an end-to-end method of getting high-resolution photo-realistic facial images from low-resolution (LR) in-the-wild images without losing the facial identity details. The pipeline used a flexible stacked GAN structure for the SR process with different target image resolutions on different upscaling factors. To avoid getting blur or nonsensical image output and realize the flexibility, "U-Net" architecture and upsampling layers with residual learning blocks were stacked. The stacked network structure makes applying different loss functions in different parts of the network possible, which helps to solve the two problems of keeping identical facial details of the LR input image and generating high-quality output images simultaneously. By using 3 different loss functions in different positions of the stacked network separately, through experimental comparison, we found the best stacked residual block parameters which could get the best output image quality. Experimental results also explicated that the network had a good SR ability compare to state of the art methods in different resolution and upscaling factor. (C) 2020 Elsevier B.V. All rights reserved.

提出了基于布料模拟滤波和随机森林的点云分类的方法.通过布料模拟滤波生成的地面点云进行高程值归一化,可以削减地形变化对点云分类精度的影响.对比未归一化结果,分类精度有30％的提升.把点云信息与遥感光谱信息融合进一步提高分类精度,对比其他分类结果有3％到5％的提升.

Fe Ⅻ line (19.5 nm) is one of important targets of imaging detection in solar spectrum, and 19.5 nm multilayer mirrors were employed to reflect 19.5 nm line and suppress sidelobe. 19.5 nm multilayer mirrors with a bandwidth of 1.0 nm are in demand in Solar X-EUV imager installed in FengYun Ⅲ satellite. Thickness ratios of Mo layer of 0.15 and 0.11, respectively, are utilized in multilayer mirrors at normal and 45° incidence. The influence of roughness/diffusion on reflectance is discussed, and profile changes of substrate after deposition are also analyzed.

The stability of Cr/C multilayer during irradiation or thermal annealing was investigated using grazing incidence X-ray reflectivity measurement, X-ray photoelectron spectroscopy, X-ray diffraction analysis, small-angle X-ray scattering analysis, and soft X-ray reflectivity measurement. One sample was irradiated with a white beam of synchrotron radiation and five other samples were annealed at various temperatures. The 18-h irradiation treatment caused local surface contaminants but did not affect the buried stacks. The annealing treatment resulted in increased reflectivity at approximately 1.2 keV, and the multilayer remained stable for temperature up to 700 °C. Thus, the Cr/C multilayers exhibited excellent stability during irradiation and thermal treatments and can be used for the mirrors and multilayer gratings of third-generation synchrotron radiation systems.