Studies of multilayer structure in depth direction by soft X-ray spectroscopy

1 Introduction Over the recent several decades, artificial layered structures have been extensively developed as useful functional structures for semiconductor devices [1], magnetic devices [2], X-ray high-reflectance mirrors [3], and so on. They are initially designed as multilayers consisting of uniform layers with the same properties as those of bulk materials and having clear-cut inter- faces (boundaries). However, in real cases, some lay- ers have structures different from those of bulk m…     

U-10Mo/Al-Si固体扩散行为

采用扩散偶方法研究U-10Mo合金与Al-xSi(x＝0,1,2,5,7,9,质量分数)合金的固体扩散行为。实验在真空热压炉中完成,退火温度为555、570、580、590和595℃,时间为5～10h。实验结果表明：退火条件对扩散行为有显著影响,580℃是U-10Mo/Al-xSi扩散行为的重要分界点;当温度低于580℃热压退火处理时,扩散层厚度随Si含量的增加先急剧减小然后缓慢增大;当温度高于580℃时,扩散层的厚度随Si含量的增加而增加。Si含量较高(≥2%)的扩散偶扩散层厚度比低Si含量的小,扩散层呈3层结构,靠近Al-Si侧出现贫Si区。成分分析显示：Si含量较高的扩散偶,靠近U-Mo侧的扩散薄层中出现Si的富集,其成分为(U,Mo)(Al,Si)_x (x≤3);靠近Al-Si合金侧的扩散层成分为(U,Mo)(Al,Si)_x (x＞3)。     

Kinetic study of wet oxidation of Si0.5Ge0.5 alloy by Rutherford backscattering spectroscopy

1IntroductionSilicongermaniamalloyshavereceivedgreatattentioninrecentdecadefOrtheirpo-tentialapplicationinadvancedelectronicandoptoe1ectronicdeyices[1~41.Theoxidationbehaviorofthismaterial,however,continuestobeatroublesomeissuethatimPedesitstAnelydevelopment.Previousresearchesdemonstratedthathighgermaniamcontent,inthealloyandlowtemperaturecouldformaAnxtureoxidelayeIofSiO, GeOgst'].WhengermaniumconcentrationisloweIonlySiO2fo...d[7'8].Inthepresentstudy,OkidationhasbeenpeIformedat8oO'Cand9…     

Structural analysis of DC magnetron sputtered and spin coated thin films using RBS, TEM and X-ray reflectivity methods

Metallic thin films such as Au, Cr, Ag, etc., on silicon substrate have many technologically important applications as contact layers in microelectronic industry, as reflecting mirrors in synchrotron radiation research, etc. The native oxide layer on crystalline silicon surface inhibits wetting of few nm thick Au or Ag on native oxide/silicon systems. To obtain continuous thin metallic films (a few nm thick), a Cr layer was first deposited as a adhesion layer on the Si substrate. In this paper, Rutherford backscattering analysis (RBS) of Si/Cr/SiO₂/Si, Si/Au/SiO₂/Si, Si/Au/Cr/SiO₂/Si and Polystyrene (PS) polymer coated on some of these bi- or tri-layer structures has been reported. The X-ray reflectometry and transmission electron microscopy studies were carried out to complement the RBS measurements. The thickness, surface and interface roughness, and crystalline quality have been determined.     

Development of Wide Band Neutron Monochromator Consisting of a Stack of Multilayers

A wide band neutron monochromator consisting of a stack of four multilayers on two Si wafers has been developed. One multilayer has 201 Ni/Ti layers. The layer thickness is gradually changed in order to extend the neutron reflection wavelength range similar to a supermirror. Multilayers were fabricated by the vacuum evaporation methods on each side of a Si substrate of 225 μm in thickness. Neutron reflectivity was measured by the θ-2θ reflectometer using cold neutrons. The neutron reflection wavelength was broadened to 19–40 nm by this stack from 26–40 nm of one multilayer.     

Three dimensional measurement of nanostructures by single event TOF-RBS with nuclear nano probe

Single, double and triple-layer test structures were measured by time of flight (TOF) Rutherford backscattering spectrometry (RBS) for checking the sensitivity and resolution. A single-layer nanostructure with Au stripes on a Si substrate was resolved by TOF-RBS measurement within a short time of 256 s. The spatial resolution, measured by the edge of the Au stripes, was 42 nm. Another single-layer nanostructure with Pt stripes fabricated by electron beam (EB) induced deposition on a Si substrate was resolved by TOF-RBS measurement even at a thickness of Pt stripes less than one mono-layer. Ga embedded layers implanted by a focused ion beam under the Pt stripes fabricated by EB induced deposition on a Si substrate could be detected for a double-layer nanostructure. Furthermore, a triple-layer nanostructure with two Pt stripe layers isolated by a SiO₂ layer fabricated by EB induced deposition on a Si substrate could be resolved and cross-sections shown.     

The effect of oxides on PIXE measurements

The presence of oxides on metallic samples used for PIXE analysis affects quantitative measurements. This effect has been calculated based on thick target analysis on layers of different compositions. The ratio of oxidized metal yield to clean metal yield is seen to depend on proton energy and on oxide thickness. Calculations are presented for oxides of Al, Si, Fe, and Cu, and applied to experimental data on Si. The method may be applied to measuring thicknesses of oxides of known stoichiometry.     

Xenon-ion irradiation of Co/Si bilayers: Effects of interface structure and ion energy

Heavy-ion irradiation of ferromagnetic thin layers changes their micromagnetic and microstructural properties, due to the production of defects, relaxation or build-up of stress, or changes of grain size. When the ion range exceeds the layer thickness, ion mixing processes take place, leading to the formation of silicide phases. The present study deals with Co(30 or 55 nm)/Si bilayers irradiated at room temperature with 100- or 200 keV Xe ions to fluences of up to 15 × 10¹⁵/cm². The Si(1 0 0) wafers were either crystalline or pre-amorphized by 1 keV Ar⁺ implantation. Rutherford backscattering spectroscopy, in-plane magneto-optical Kerr effect, and X-ray diffraction served to analyse the samples before and after irradiation. The results will be compared with those obtained for other heavy-ions for Co/Si bilayers and in similar studies on Fe/Si bilayers.     

RBS analysis of front contacts for surface-barrier detectors

Surface-barrier detector structures based on Au, WTi and Au/WTi contacts on (111) n-Si were analysed. The metal layers were deposited by evaporation or sputtering to 40–100 nm thicknesses. The aim was to improve the thermal stability of the surface-barrier structures and retain the favourable detector properties of the Au/Si system. Contact structures which contain WTi layers have shown a much better thermal stability compared to the Au/Si system, but the properties of the detectors were poorer. The probable reasons are the reactivity of W and Ti with the thin oxide layer on the silicon surface and perhaps the higher energy of adatoms during sputter-deposition. Both effects can influence the degradation of the surface-barrier properties.     

用计算机程序来计算复合镀层厚度

自从1974年西德H.Ebel等人首先使用基本参数法X射线荧光分析技术绝对测量薄层厚度以来,已经有许多人在改进这项技术,并取得了进展。使用这种方法可以不需要任何标准样品,非破坏性地绝对测量几乎任意材料组合的镀层厚度。但是这些方法都局限在单镀层,而在生产中常见的是复合镀层。如铜基上镀镍再镀金;铁基上镀铜再镀镍;黄铜上镀银再镀金等。对于复合镀层,美国R.J.Russell在1977年研究了多层之间二次荧光对测量结果的影响。     

基于脉冲激光单粒子效应的二次光斑研究

脉冲激光可有效模拟重离子触发芯片的单粒子效应。本工作在应用背部激光试验方法辐照芯片时观察到了二次光斑现象,通过Si衬底和Si晶圆片研究了芯片单粒子效应实验中二次光斑的成因。实验结果表明,二次光斑主要是由于激光在芯片有源区附近的金属布线层反射形成的。通过测量芯片的Si衬底厚度以及激光触发芯片单粒子效应时的聚焦深度,实验验证了二次光斑是在金属布线层区域形成的。     

An enhanced differential evolution-based inverse radiation transport model for identification of unknown shielding layer thicknesses with gamma-ray spectrum

Identifying the geometric information of an object by analyzing the detected radiation fields is an important problem for national and global security.In the present work,an inverse radiation transport model,based on the enhanced differential evolution algorithm with global and local neighborhoods (IRT-DEGL),is developed to estimate the unknown layer thickness of the source/shield system with the gamma-ray spectrum.The framework is briefly introduced with the emphasis on handling the enhanced differential evolution algorithm.Using the simulated gamma-ray spectra,the numerical precision of the IRT-DEGL model is evaluated for one-dimensional source systems.Using the detected gamma-ray spectra,the inverse investigations for the unknown thicknesses of multiple shielding layers are performed.By comparing with the traditional gamma-ray absorption method,it is shown that the IRT-EDGL model can provide a much more accurate result and has great potential to be applied for the complicated systems.     

单晶硅表面钝化层在低能电子辐照前后的SIMS和XPS分析

为了研究低能电子辐照对单晶硅器件表面钝化材料中产生的化学微结构的变化,在轻掺杂P型单晶硅基底上制作了三种表面钝化膜,分别是单一SiO2钝化膜、SiO2/Si3N4复合钝化膜、硼硅玻璃/Si3N4复合钝化膜,开展了表面钝化单晶硅在最大能量70 keV的加速器电子束下的辐照实验.样品在空气气氛下辐照6 h,用二次离子质谱(...     

Structural characterization of amorphous Fe–Si and its recrystallized layers

We have synthesized amorphous Fe–Si thin layers and investigated their microstructure using transmission electron microscopy (TEM). Si single crystals with (1 1 1) orientation were irradiated with 120 keV Fe⁺ ions to a fluence of 4.0 × 10¹⁷ cm⁻² at cryogenic temperature (120 K), followed by thermal annealing at 1073 K for 2 h. A continuous amorphous layer with a bilayered structure was formed on the topmost layer of the Si substrate in the as-implanted specimen: the upper layer was an amorphous Fe–Si, while the lower one was an amorphous Si. After annealing, the amorphous bilayer crystallized into a continuous β-FeSi₂ thin layer.     

The cyclic nature of corrosion of zircaloy-4 in 633 K water

Optical and electron microscopic examination of cathodic-vacuum-etched cross-sections of corrosion films on zircaloy-4, produced during 108.86-Ms (1260-day) tests in 633 K water, revealed alternate dense columnar-grained layers and narrow porous layers lying parallel to the metal surface, but no through-thickness openings except at corners. Correlation of layer structures with corrosion test data indicates that the corrosion process consists of repeated cycles of cube-root kinetics. During each cycle, a new protective layer grows at the metal-oxide interface. At a critical thickness, the layer suddenly becomes non-protective, causing transition to the initially rapid corrosion rate of a new cycle. Porous layers mark the location of the interface at the time of each transition. Variations in post-transition corrosion rates are related to variations in the cube-root rate constant, average film density, and critical layer thickness. A stress-controlled corrosion mechanism is proposed.     

Fabrication of Total-Dose-Radiation-Hardened (TDRH) SOI wafer with embedded silicon nanoclusters

Si ion-implantation and post annealing of silicon wafers prior to wafer bonding were used to radiation-harden the thermal oxide layer of Silicon on Insulator structures. After grinding and polishing, Total-Dose-Radiation-Hardened SOI (TDRH-SOI) wafers with several-micron-thick device layers were prepared. Electrical characterization before and after X-ray irradiation showed that the flatband voltage shift induced by irradiation was reduced by this preprocessing. Photoluminescence Spectroscopy (PL), Transmission Electron Microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) results indicated that the improvement of the total dose response of the TDRH-SOI wafer was associated with formation of Si nanoclusters in the implanted oxide layer, suggesting that these were the likely candidates for electron and proton trapping centers that reduce the positive charge buildup effect in the buried oxide.     

Diffusion and strain relaxation in Si/Si1−xGex/Si structures studied with Rutherford backscattering spectrometry

The thermal stability of strained Si/Si_1−xGe_x/Si structures grown by molecular beam epitaxy was investigated by resistive heating and in situ Rutherford backscattering spectrometry. Ge profiles obtained from a 50 nm Si_1−xGe_x layer on a Si(100) substrate capped with 50 nm Si were evaluated for different Ge concentrations after sequential heating periods at a particular temperature between 850 and 1010° C. The diffusion coefficients, calculated from the increase in signal in the tail of the Ge profile, proved to be comparable to the value for Ge in bulk Si. A more pronounced decrease of the signal at the center of the Ge profile indicated a faster diffusion within the SiGe layer which was confirmed by analysis of the FWHM of the Ge profile. Ion channeling measurements were used to characterize tetragonal strain in the buried SiGe layers. Angular scans through the 111 direction were interpreted with Monte Carlo channeling calculations and used to study strain relaxation in dislocation-free and partially relaxed layers.     

塑料闪烁光纤阵列探测器的结构设计

具有多层阵列结构的塑料闪烁光纤探测器可实现土壤中⁹⁰Sr含量的直接、快速测量,闪烁光纤阵列结构和信号处理方式是提高⁹⁰Sr含量测量精度和抗γ射线干扰能力的关键参数。本文利用蒙特卡罗方法对探测器建模和计算,优化了探测器的结构。推荐的闪烁光纤阵列探测器为5层结构,第4层为厚度不小于6 mm的聚甲基丙烯酸甲酯（PMMA）吸收层,其他层为厚度1 mm的双涂层方形塑料闪烁光纤阵列。第1~3层信号符合后输出,可提高探测器对γ射线的甄别能力。     

RBS investigations of buffer layers between YBa2Cu3O7−x and silicon

The deposition of high-quality high-T_c superconducting films on silicon wafers for future hybrid electronic devices is strongly hampered by the interdiffusion between films and substrate. This effect degrades the superconducting properties seriously and is a strong function of temperature. Since high processing temperatures are inevitable for good films, suitable buffer layers are needed to reduce the interdiffusion. We have investigated the combinations ZrO₂/Si(100), BaF₂/Si(100), and noble-metal/TiN/Si(100) at temperatures up to 780°C in oxidizing ambient. YBa₂Cu₃O_7−x films have been deposited onto the buffer layers by laser ablation. Thereafter the interfaces have been analyzed by Rutherford backscattering. So far only ZrO₂ has demonstrated sufficient stability to serve as a buffer layer for the laser-ablated YBa₂Cu₃O_7−x films. All other combinations suffer from interdiffusion or oxidation.