Institutional Repository of Institute of Modern Physics, CAS
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Creation of nanodots on mica surfaces induced by highly charged xenon ions
No full text<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">Experiments on nanostructure formation on muscovite mica surfaces irradiated by highly charged Xe29+ ions with a beam energy of 0.58 MeV and Xe30+. ions with two beam energies (0.6 MeV and 4.8 MeV) have been carried out on the 320 kV ECR platform at the Institute of Modern Physics (IMP), Lanzhou. The created nano-sized structures have been imaged using tapping mode atomic force microscopy. Hillock-like structures are clearly visible at the surface of the mica irradiated by Xe29+ ions (at 0.58 MeV) below the charge state threshold reported in earlier experimental investigations with a height (similar to 1.6 rim) nearly equal to the one observed by Xe30+ ions (at 0.6 MeV). Moreover when mica is irradiated by Xe30+ ions (at 4.8 MeV), regular nanodots have been observed with a surprisingly larger height of 3.3 nin, nearly the double than the one created by the impact of Xe30+ ions with kinetic energy of 0.6 MeV. The possible mechanism of insulator surface modification is discussed. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.</span
Thresholds for kinetic and potential energies of Arq+ induced Au target atomic Malpha-X rays emission
No full text<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">The X ray emissions from Arq+ (the kinetic energy 150 keV and 1.2 MeV) beams impinging on Au surface are measured. The results show that the about 2 keV minimum-potential energy of Ar11+ and Ar12+ (150 keV) is necessary for exciting Au atoms to emit M-alpha-X rays. The kinetic energy threshold for exciting target atomic X ray emission is estimated by the semiclassical approximation theory of binary collision.</span
The test pulse line ion accelerator in Lanzhou
No full text<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">To accelerate intense, short pulsed heavy ion beams to the energies of interest for studies of high energy density physics and warm dense matter, the Pulse Line Ion Accelerator (PLIA), of which the axial acceleration gradient can achieve several MeV per meter with realistic helix parameters at very low cost, was developed in recent years. A simple prototype of PLIA for a proof-of-principle experiment called the Lanzhou Test PLIA was designed and constructed at the Institute of Modern Physics in Lanzhou, and the test result matches the calculated result well. The pattern of the axial electric field Ez and the velocity of the traveling wave were simulated by CST.</span
Study of ion beam transport from the SECRAL electron cyclotron resonance ion source at the Institute of Modern Physics
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离子治癌加速器数字电源调节系统
No full text本实用新型涉及一种基于NiosII双核的离子治癌加速器数字电源调节系统，可以适用于离子治癌加速器多种拓扑类型的高精度数字电源脉冲和直流运行方式。一种离子治癌加速器数字电源调节系统，包括FPGA芯片，Flash模块、内存单元同步动态随机存储器、同步静态随机存取存储器、系统的调试接JTAG接口、以太网芯片、光纤接收器、通用异步接收/发送装置串行通信设备和串行存贮器、ADC模数转换器、DAC数模转换器、用电源故障保护信号输入通道模块和脉宽调制信号输出通道模块均与FPGA芯片的管脚相连，还包括FPGA芯片上系统
Narrow size distribution of Au nanocrystals formed in sapphire by utilizing Ar ion irradiation and thermal annealing
No full textWe describe a method to form narrow size distribution of Au nanoparticles in Al2O3 substrate. A layer of Au about 30 nm thick was deposited on surface of single crystalline Al2O3, and then was brought into the matrix by Ar ion irradiation to form Au nanoparticles. The size distribution of the nanoparticles was subsequently modified by annealing treatment. Rutherford Backscattering Spectrometry, X-ray Diffraction and Transmission Electron Microscopy were used to study the structure and the size distribution of the nanoparticles. The results show that a narrow size distribution of nanoparticles formed in single crystalline alumina with an average diameter of 3.9 nm and a standard deviation of 0.5 nm. (C) 2012 Elsevier B.V. All rights reserved
纳米硬度
No full text<span style="font-family: 'Microsoft Yahei', 宋体, Arial, ' Helvetica', ' sans-serif'; font-size: 13px; line-height: 22px;">碳化硅（SiC）有着良好的物理和化学性质，这使它有着广泛的应用前景，比如在半导体和核能工业等。研究载能离子辐照对SiC微观结构的损伤及宏观性能的改变规律，为这类材料广泛的应用有着重要的意义。本论文的研究主要围绕载能Xe离子辐照SiC晶体引起的微结构损伤、缺陷积累和演化及力学性能的变化开展的。 利用多个动能(3.8-8 MeV范围)的Xe离子在选定剂量下依次注入6H-SiC样品，使Xe原子浓度在样品深度850-1800 nm范围内均匀分布，并且使Xe原子浓度分别达到7.5,30和150 at.ppm；退火实验在真空下进行，退火温度分别为773,1073和1373 K；利用高分辨XRD，拉曼光谱和透射电镜（TEM）研究了辐照和退火前后SiC的微结构损伤、缺陷积累和演化，并且利用纳米压痕仪研究了SiC的力学性能的变化。 在7.5 at.ppm Xe浓度的样品中，HRXRD与拉曼光谱的结果表明SiC的晶格损伤主要体现在晶格发生膨胀性应变上，而TEM的结果表明损伤的程度还没有达到完全无序性。缺陷的类型主要以点缺陷为主，间隙型缺陷是SiC辐照之后晶格膨胀主要原因。在退火的过程中，各种缺陷发生进一步的扩散，复合和演化，使晶格损伤逐渐恢复。应变晶格恢复的减小量符合Arrhenius定律。由此计算出的晶格应变激活能小于理论计算的间隙子的移动能。 拉曼光谱和TEM的结果表明在30 和150 at.ppm注Xe浓度样品中都出现了非晶层，其中30 at.ppm注Xe浓度样品中出现的是非晶化的埋层，而150 at.ppm注Xe浓度样品注入区域已经全部非晶化。HRXRD结果表明：在退火之后在主峰附近重新出现的卫星峰可能来自于非晶层和晶体层之间过渡区域的应变晶体埋层。卫星峰对应的晶格应变值随着退火温度升高而减小，并且与注入的剂量无关。另外，拉曼光谱结果表明C类的缺陷在退火温度为773-1073 K已开始移动，而Si类缺陷明显的移动发生在1373 K。最后TEM 的结果表明非晶化是辐照肿胀的原因之一。辐照引起SiC微结构的损伤导致了力学性能的改变。样品7.5 at.ppm的纳米硬度明显的超过了空白样品，而对于出现非晶化的样品30 和150 at.ppm来说结果是不同的。当SiC样品注入区域完全非晶化的时候，硬度下降了45%左右。</span><span style="font-family: 'Microsoft Yahei', 宋体, Arial, ' Helvetica', ' sans-serif'; font-size: 13px; line-height: 22px;">/* Generator: eWebEditor */ p.MsoNormal, li.MsoNormal, div.MsoNormal {margin:0cm;margin-bottom:.0001pt;text-align:justify;text-justify:inter-ideograph;font-size:10.5pt;font-family:"Times New Roman";} div.Section1 {page:Section1;} Silicon carbide (SiC) possesses outstanding physical, chemical and electronic properties that make it very promising for applications in semiconductors, advanced nuclear reactors and nuclear waste technology. Studies on the accumulation of radiation damage and gaseous impuries in SiC are of primary importance. In the present work，the microstructure damage，defects accumulation and evolution，and mechanical properties of SiC irradiated by multiple-energy Xe ions were studies. Specimens of 6H-SiC were implanted with Xe ions with multiple kinetic energies ranging from 3.3 to 8 MeV at room temperature to obtain nearly uniform Xe concentrations, in the depth between 850 and 1800 nm, to 7.5, 30, 150 at.ppm, respectively. The irradiated specimens were subsequently thermally annealed under high vacuum at temperatures of 773, 1073 and 1373 K, respectively. The lattice damage and defect evolution were studied by high resolution x-ray diffraction spectrometry (HRXRD), Raman scattering spectroscopy, and transmission electron microscopy (TEM)，while changes in mechanical properties were analyzed by the nanoindentation measurement in the continue stiffness mode. In the specimen Xe-implanted to a concentration of 7.5 at.ppm Xe, HRXRD and Raman scattering results suggest that the irradiation damage mainly induce the lattice expansion in the implanted SiC, while TEM results show that the the implanted layer keeps crystalline state. The main species are point defects. Interstitial-type point defects are supposed to play a major role in the lattice expansion. Upon subsequent thermal annealing the strain relaxes gradually. The relaxation of the strain follows Arrhenius plot. The obtained apparent activation energy of strain relaxation (Ea=67±5 meV) is lower than the value of interstitial migration energy from theoretical calculations, possibly due to the migration of interstitial defects enhanced by the strain gradient. In the specimens implanted to 30 at.ppm and 150 at.ppm Xe， formation of amorphous layers is confirmed from Raman spectrum and TEM results. The buried amorphous layer is observed in the 30 at.ppm Xe implanted specimens, while the implanted region of the 150 at.ppm-Xe specimens has been completely amorphized from the specimen surface. HRXRD results show that the satellite peak near the main peak reappears after thermal annealing which may not be from the surface region but from a buried strain layer between the amorphous layer and the unperturbed bulk crystal. The strain value related to the satellite peak decreases with increasing annealing temperature and is independent of the ion fluence. In addition, Raman spectrum studies indicate that carbon-type defects begin to migrate at annealing temperatures from 773 to 1073 K, but Si-type defects diffuse obviously at a higher annealing temperature of 1373 K. The amorphization is ascribed to the observed volume swelling of the irradiated SiC.Microstructure changes due to irradiation can alter the mechanical properties. The nanohardness value of the specimen implanted to 7.5 at.ppm exceeds that of virgin SiC, whereas it is opposite in the cases of 30 at.ppm and 150 at.ppm Xe implantation due to the formation of amorphous regions. When complete amorphization is reached, the hardness value decreases strongly by about 45%, which is in agreement with previous work.</span
The application of irradiation defects in synthesis of metal nanoparticle in insulator
No full text本论文的核心思想是尝试利用辐照缺陷来调控金属纳米颗粒形核，期望达到改善绝缘基体（镁铝尖晶石）中金属纳米颗粒尺寸的离散性和分布的均匀性。首先采用不同能量的Ar离子在350℃下辐照表面沉积Au薄膜的样品，以达到同时在样品近表面区域引入缺陷和Au原子。实验结果发现，入射离子的动能对Au纳米颗粒的形成有较大贡献。退火过程中发现Au纳米颗粒的热稳定性并不理想，因此对实验方案做了改进，采用更高能量的Ar离子辐照，同时样品表面沉积原子质量较轻的Cu薄膜。辐照后样品的TEM结果显示Cu颗粒的直径分布在1.3-3.4nm之间，并且颗粒的热稳定性显著改善。但是样品表面的Cu在高温下发生了团聚，这对样品的光学性能有一定影响。为了避免表面金属的影响，随后将Ag离子直接注入到Ar离子辐照损伤层。UV-VIS谱的结果显示缺陷的引入显著地增强了Ag纳米颗粒的形核，PAS多普勒展宽谱的结果表明对Ag纳米颗粒形核起到促进作用的主要是空位型缺陷，TEM结果显示缺陷的引入不仅促进了Ag纳米颗粒的形核，而且改善了Ag纳米颗粒尺寸的离散性及分布的均匀性。在后续的退火实验中发现在600-700℃范围内，镁铝尖晶石的Mg2+和Al3+离子所在的位置发生了反转，引起晶格常数的增大，但是阳离子位置的反转并不影响材料的结晶度。 Because of having merits of both traditional composites and nanomaterials, the composites of dielectrics embedded with metallic nanoparticles have a broad application in many fields. However, there is no an effective way to improve the size discreteness and distribution uniformity of nanoparticles to this day. The core idea of this dissertation is using irradiation defects to adjust the nucleation of metallic nanoparticles for improving the nanoparticles size discreteness and distribution uniformity. In experiment Ar ions were used to irradiated the magnesium-aluminum spinel deposited with Au film on surface at elevated temperature to introduce defects and metal atoms simultaneously in near surface region. It was found that the kinetic energy of incident ions seems to have a greater contribution to metal nanoparticles formation than irradiation fluence, and Au nanoparticles were unstable in the annealing process. Based on these results Cu instead of Au was deposited on specimen surface and Ar ions with higher kinetic energy were used in subsequent experiment. After irradiation the observation of SPR absorbance peak in UV-VIS spectrum indicated the formation of Cu nanoparticles. TEM results revealed that Cu nanoparticles with diameter of 1.3-3.4nm dispersed in the matrix. The Cu nanoparticle thermal stability has also been improved evidently. However, the agglomeration of Cu, which had an influence on the specimen’s absorbance property, occurred on surface at elevated temperature. To avoid the influence of metal film on absorbance property Ag ions were implanted directly into the layer rich in irradiation defects produced by Ar ions irradiation in the next experiment. UV-VIS results showed enhanced nucleation of metallic nanoparitlces in the specimen rich in defects. PAS Doppler broadening spectrum identified that the defects promoted the nucleation of metallic nanoparticle were vacancy type defects. TEM results revealed that the introduction of irradiation defects can improve the size discreteness and distribution uniformity. In subsequent annealing experiment it was found that the inversion of Mg2+ and Al3+ occurred in temperature range of 600-700℃，which caused the increase of lattice constant, but had little influence on specimen crystallization. 
