电子束在VO2薄膜中引起的价态、相结构和光学性能的改变

 利用能量为1.7MeV, 注量分别为1.25×10¹³/cm², 1.25×10¹⁴/cm², 1.25×10¹⁵/cm²的电子束辐照VO₂薄膜,采用XPS, XRD等测试手段对电子辐照前后的样品进行分析,并研究了电子辐照对样品相变过程中光透射特性的影响。结果表明电子辐照引起VO₂薄膜中V离子出现价态变化现象,并使薄膜的X射线衍射峰发生变化。电子辐照在样品中产生的这些变化显著改变了VO₂薄膜的热致相变光学特性。     

钛离子辐照对MgB2超导薄膜的载流能力和磁通钉扎能力的影响

利用混合物理化学气相沉积法(hybrid physical-chemical vapor deposition, HPCVD)可以制备出高性能的MgB₂超导薄膜, 再对薄膜进行钛(Ti)离子辐照处理.经过辐照处理后的样品被掺入了Ti元素, 与未处理的干净MgB₂样品相比,其超导转变温度没有出现大幅度的下降, 而在外加磁场下的临界电流密度得到了明显的提高,同时样品的上临界磁场也得到了提高. 在温度5 K, 外加垂直磁场为4 T的情况下, Ti离子辐照剂量为1× 10¹³/cm²的样品的临界电流密度达到了1.72× 10⁵ A/cm², 比干净的MgB₂要高出许多,而其超导转变温度仍能维持在39.9 K的较高水平.     

Si离子注入和H等离子体处理对单晶Si中空腔生长的影响研究

室温下首先采用160keVHe离子注入单晶Si样品到剂量5×10¹⁶ions/cm²,部分样品再接受80keVSi离子辐照到较高的剂量5×10¹⁵ions/cm²或接受高密度H等离子体处理.应用透射电镜观测分析了800℃高温退火引起的空腔的形成形貌.结果表明,附加Si离子辐照或H等离子体处理会影响Si中空腔的生长.就Si离子附加辐照而言,由于辐照引入富余的间隙子型缺陷,因此,它会抑制空腔的生长,而高密度H等离子体处理则有助于空腔的生长.定性地讨论了实验结果.     

110keV质子辐照温控涂层性能变化的XPS分析

实验研究了注量在1.0×10¹¹—1.0×10¹⁶p/cm²范围依次变化时110keV质子辐照引起的温控涂层热光性能的变化,并使用XPS谱仪分析了辐照样品化学态的变化. 实验结果表明,质子注量不高于1.0×10¹⁴p/cm²时,同种材料的温控涂层样品的相对光反射率变化很小,同时同种材料样品的表面化学结构如化学位移和元素的比例变化很小.当注量高于1.0×10¹⁴p/cm²时, 样品的相对光反射率变化明显,样品表面的原子化学结构变化大, 化学位移明显增加, 元素比例变化显著,所有样品表面的C元素比例明显增大而O元素比例明显减小.一定注量的低能质子辐照能够使某些低太阳吸收率α_s的温控涂层的太阳吸收率变得更低, 具有改善热光性能的效果.质子辐照之后温控涂层样品表面化学结构的变化与样品的物理性能的变化存在直接的关联.     

电子通量对ZnO/K2SiO3热控涂层光学性能的影响

 研究了电子通量对ZnO/K₂SiO₃热控涂层光学性能的影响。分别采用通量为5×10¹¹/cm²·s，8×10¹¹/cm²·s，1×10¹²/cm²·s 和5×10¹²/cm²·s的电子对试样进行辐照。电子辐照下涂层的光学性能发生了退化，并且发现了退化涂层在空气中的“漂白”现象。分析了ZnO/K₂SiO₃热控涂层光学性能的退化机制，同时讨论了电子通量对太阳光谱吸收系数的影响。实验结果发现，在5×10¹¹～1×10¹²/cm²·s的电子通量范围内，电子通量对ZnO/K₂SiO³热控涂层光学性能的影响相同。因此在这个电子通量范围内，采用加速地面试验来模拟空间的电子辐照效应是有效的。     

国产高Z闪烁晶体的辐照损伤研究

在总强度为10⁵Ci^的60Co γ射线辐照装置上开展了国产高Z闪烁晶体的辐照损伤研究.在5×10³—7.5×10⁵rad剂量范围内测量了小尺寸BGO晶体样品的辐照损伤效应,观察到损伤随剂量增加逐渐趋于饱和的现象;辐照损伤的自然恢复过程可用三组时间常数表征的指数函数描述.在5×10⁵rad剂量下,考察了BaF₂,CsI(Tl)以及ZnWO₄晶体小尺寸样品的辐照损伤效应.发现了BaF₂的严重损伤情况,初步分析原因可能是晶体中某些微量杂质的存在.     

Ti-2Al-2.5Zr合金He离子辐照效应研究

 在Ti-2Al-2.5Zr合金中注入能量为75 keV的He离子，注入剂量分别为5×10¹⁶cm^-2，1×10¹⁷ cm^-2。通过显微硬度测量和剖面电子显微观察，研究了He离子对Ti-2Al-2.5Zr合金力学性能和显微组织的影响。结果表明:样品的显微硬度随He离子注量的增加而升高，在温度为350和550 ℃的Ar气中退火后硬度有所下降。剖面电子显微观察发现有位错环和He气泡生成，退火后He气泡有长大、缺陷有回复的趋势。辐照产生的位错环是辐照后硬度升高的直接原因，其退火发生回复又引起硬度随退火温度的升高而降低。     

重离子背散射——测量表面与近表面痕量元素的一种新方法

本文报道了用重离子背散射探测表面、近表面微量重元素的新方法。通过选择入射离子种类,使入射离子原子量M₁等于或略大于基体原子量M₂,利用弹性散射运动学实现自动排除探测系统的脉冲堆积现象。实验结果表明利用能量为3MeVSi离子背散射,测量基体Si中注As的灵敏度优于2×10¹²原子/cm²;对基体Si表面的杂质元素Au,探测灵敏度高达2.2×10⁹原子/cm²。     

高能Pb离子辐照注碳SiO2的红外谱研究

室温下，先用120keV的C离子注入二氧化硅薄膜样品至剂量2.0×1017、5.0×1017或8.6×1017ions/cm2，再用950MeV的Pb离子分别辐照至剂量5.0×1011、1.0×1012或3.8×1012 ions/cm2，然后测量样品的傅里叶变换红外(FTIR)光谱. 通过分析测量得到的傅里叶变换红外谱，发现Pb离子辐照在注碳SiO₂样品中可引起大量的Si－C和Si (C)－O－C等化学键的形成，大剂量Pb离子辐照可在大剂量注碳的SiO₂中产生分子CO₂. 大量的Si－C键的存在和分子CO₂的形成，预示着高能Pb离子辐照在注碳SiO₂样品中有可能形成了纳米Si团簇和/或SiC晶粒.     

LiNbO3和LiTaO3晶体Er3+/Yb3+掺杂水热外延层室温吸收光谱分析

本文引入与浓度和厚度有关的k_NL待定参数, 在J-O理论基础上, 对Er³⁺/Yb³⁺掺杂的LiNbO₃和LiTaO₃单晶衬底上 的多晶水热外延样品进行了基于吸收光谱的拟合计算. LiNbO₃:Ω₂=2.34× 10^-20 cm², Ω₄=0.77× 10^-20 cm², Ω₆=0.31×10^-20 cm², k_NL=4.32× 10^-2 mol·m^-2. LiTaO₃:Ω₂=1.68×10^-20 cm², Ω₄=0.84×10^-20 cm², Ω₆=0.45×10^-20 cm², k_NL=9.17×10^-3 mol· m^-2. 该方法可尝试推广到粉体或胶体等难以直接获得浓度和厚度数据的体系. 经上转换发光测试及光谱参数计分析认为Er³⁺/Yb³⁺离子的掺杂浓度比为1:1的情况下, 样品呈现绿色上转换发光光谱; 可尝试以降低基质声子能量的方法提高⁴I_13/2能级 对²H_11/2和⁴S_3/2能级的量子剪裁效率.     

Spectroscopic ellipsometric evidence of the solid-state reactions in Ni/Si multilayered films,induced by ion-beam mixing and thermal annealing

Solid-state reactions, induced by ion-beam mixing (IBM) and thermal annealing, in Ni/Si multilayered films (MLF) with an overall stoichiometry of Ni2Si, NiSi and NiSi2, while keeping the nominal thickness of Ni sublayer constant (3.0 nm), were studied by using spectroscopic ellipsometry as well as X-ray diffraction (XRD). The mixing was performed with Ar+ ions of an energy of 80 keV and a dose of 1.5× 1016 Ar+/cm2. Unlike the results of our previous study on Fe/Si MLF [Y.V. Kudryavtsev et al., Phys. Rev. B 65, 104417 (2002)], it was shown that an amorphous phase of NiSi in the B20 phase was formed during deposition independent of the overall stoichiometry of MLF, i.e., the nominal thickness of Si sublayer. IBM leads to some structural changes in the Ni/Si MLF, which cannot be detected by XRD but are confidently recognized by optical tools. A thermal annealing at 673 K of the Ni/Si MLF with an overall stoichiometry of NiSi and NiSi2 causes formation of the -NiSi phase. The first trace of NiSi2 phase on the background of the -NiSi phase was detected by XRD after an annealing at 1073 K, while, according to the optical results, NiSi2 turned out to be the dominant phase for the annealed Ni/Si MLF with an overall stoichiometry of NiSi2.     

B和H离子顺次注入单晶Si 引起的缺陷及其热演变(英文)

室温下将130 keV,5x1014 cm-2 B离子和55 keV,1x1016 cm-2 H离子单独或顺次注入到单晶Si中,采用横截面试样透射电子显微镜(XTEM)和慢正电子湮没技术(SPAT) 研究了离子注入引起的微观缺陷的产生及其热演变。XTEM观测结果显示,B 和H 离子顺次注入到单晶Si 可有效减少(111) 取向的H板层缺陷,并促进了(100) 取向的H板层缺陷的择优生长。SPAT 观测结果显示,在顺次注入的样品中,B 离子平均射程处保留了大量的空位型缺陷。以上结果表明,B离子本身及B 离子注入所产生的空位型缺陷对板层缺陷的生长起到了促进作用。Abstract:Cz n-type Si (100) wafers were singly or sequentially implanted at room temperature with 130 keV B ions at a fluence of 5x1014 cm-2 and 55 keV H ions at a fluence of 1x1016 cm-2. The implantation-induced defects were investigated in detail by using cross-sectional transmission electron microscopy (XTEM) and slow positron annihilation technique (SPAT). XTEM results clearly show that sequential implantation of B and H ions into Si could eliminate the (111) platelets and promote growth of (100) platelets during annealing. SPATmeasurements demonstrate that in B and H sequentially implanted and annealed Si, more vacancy-type defects could remain in sample region around the range of B ions. These results indicat e that the promotion effect shouldbe attributed to the role of both B and B implanted induced vacancy-type defects.     

He 离子注入引起的高纯钨硬化

完成了不同注量或温度下100 keV 的He 离子注入高纯钨的实验,并利用纳米压痕技术测量了材料的微观力学性能。所有注入样品的纳米硬度值都高于未注入样品的纳米硬度值。对于室温注入样品,随着注量的增加,样品抗弹性变形能力下降;当注量不高于5x1017 ions/cm2 时,钨的纳米硬度峰值随着注量的增加而增加;注量为1x1018 ions/cm2 的钨样品的纳米硬度峰值反而降低。高温注入样品的抗弹性变形能力优于室温注入样品的抗弹性变形能力;随着注入温度的增加,样品的平均纳米硬度值和弹性模量略有下降。分析讨论了He 注入钨硬化和抗弹性形变能力降低的可能原因。Tungsten has been selected as divertor materials in fusion reactors because of its high thermal conductivity,high melting point, low expansion coefficient and high threshold energy for sputtering etc. The paper presents the hardening behaviour of high pure tungsten by 100 keV He+ with different fluences from 5x1016 ions/cm2 to 1x1018ions/cm2 at room temperature, and with fluence of 1x1018 ions/cm2 at higher temperatures (400, 600 and 800 °C). The microscopic mechanical properties of these samples were investigated by nano-indentation technology. The results show that all of the implanted samples harden obviously. The reason for hardening may be that defects of interstitial dislocation loops or dense helium bubbles etc induced by helium implantation obstacle the movement of dislocation. The peak nanohardness of the samples increased with the fluences increasing when the fluence is not more than 5x1017 ions/cm2, while the nano-hardness value of the implanted sample with the fluence of 1x1018 ions/cm2 decreases and the nano-hardness changes little in the region of 50 nm to 200 nm from surface. For all the implanted samples with 1x1018 ions/cm2 at higher temperatures, their nano-hardness values are similar, but show a trend of decrease with increasing temperature.The reason may be the decrease of the defects’ density during implantation at higher temperatures. In addition, the capability of resisting deformation for the implanted tungsten reduces with increasing fluence and increases a little at higher temperatures.     

Ar离子辐照非晶态合金表面发泡和针孔形成研究

150keV和195keVAr离子室温下辐照非晶态合金(Co₉₄Fe₄Cr₂)₇₈Si₈B₁₄,表表面发泡和溅射腐蚀是两种主要的表面损伤过程.针孔出现较表面发泡要晚,它的密度随剂量增加迅速地增加,并且在一定的辐照剂量时趋向饱和,这时,一种多孔粗糙的表面损伤结构形成.针孔的形成影响了表面发泡,导致了发泡密度随剂量增加急剧地减小.用溅射和气泡破裂解释了针孔形成和在高剂量时趋向饱和的原因.     

The role of phase separation for self-organized surface pattern formation by ion beam erosion and metal atom co-deposition

We investigate the ripple pattern formation on Si surfaces at room temperature during normal incidence ion beam erosion under simultaneous deposition of different metallic co-deposited surfactant atoms. The co-deposition of small amounts of metallic atoms, in particular Fe and Mo, is known to have a tremendous impact on the evolution of nanoscale surface patterns on Si. In previous work on ion erosion of Si during co-deposition of Fe atoms, we proposed that chemical interactions between Fe and Si atoms of the steady-state mixed Fe _x Si surface layer formed during ion beam erosion is a dominant driving force for self-organized pattern formation. In particular, we provided experimental evidence for the formation of amorphous iron disilicide. To confirm and generalize such chemical effects on the pattern formation, in particular the tendency for phase separation, we have now irradiated Si surfaces with normal incidence 5 keV Xe ions under simultaneous gracing incidence co-deposition of Fe, Ni, Cu, Mo, W, Pt, and Au surfactant atoms. The selected metals in the two groups (Fe, Ni, Cu) and (W, Pt, Au) are very similar regarding their collision cascade behavior, but strongly differ regarding their tendency to silicide formation. We find pronounced ripple pattern formation only for those co deposited metals (Fe, Mo, Ni, W, and Pt), which are prone to the formation of mono and disilicides. In contrast, for Cu and Au co-deposition the surface remains very flat, even after irradiation at high ion fluence. Because of the very different behavior of Cu compared to Fe, Ni and Au compared to W, Pt, phase separation toward amorphous metal silicide phases is seen as the relevant process for the pattern formation on Si in the case of Fe, Mo, Ni, W, and Pt co-deposition.     

Depth resolved structural study of heavy ion induced phase formation in Si/Fe/Si trilayer

Intermixing in Si/Fe/Si trilayer induced by 120 MeV Au ions has been studied. X-ray fluorescence provides information about the depth distribution of Fe atoms, while Mössbauer spectroscopy and XAFS provide information about the changes in the local structure. In the as-deposited film Fe layer is amorphous in nature with a significant Si content in it. Irradiation to a fluence of 1 ×10¹³ ions/cm² results in formation of non-magnetic intermixed layer with its hyperfine parameter close to those of Fe_0.5Si with CsCl structure. XAFS measurements under X-ray standing wave condition provide depth resolved structural information.     

Control of interlayer exchange coupling in Fe/Cr/Fe trilayers by ion beam irradiation

The manipulation of the antiferromagnetic interlayer coupling in epitaxial Fe/Cr/Fe(001) trilayers by 5 keV He ion beam irradiation has been investigated. It is shown that even for irradiation with low fluences a drastic change in strength of the coupling appears. For thin Cr spacers (below 0.6-0.7 nm) it decreases with fluence, becoming ferromagnetic for fluences above 2x10(14) ions/cm(2). The effect is connected with the creation of magnetic bridges in the layered system due to atomic exchange events caused by the bombardment. For thicker Cr spacers an enhancement of the antiferromagnetic coupling strength is found. A possible explanation of the enhancement effect is given.     

Transmission measurement based on STM observation to detect the penetration depth of low-energy heavy ions in botanic samples

The penetration depth of low-energy heavy ions in botanic samples was detected with a new transmission measurement. In the measurement, highly oriented pyrolytic graphite (HOPG) pieces were placed behind the botanic samples with certain thickness. During the irradiation of heavy ions with energy of tens of keV, the energetic particles transmitted from those samples were received by the HOPG pieces. After irradiation, scanning tunneling microscope (STM) was applied to observe protrusion-like damage induced by these transmitted ions on the surface of the HOPG. The statistical average number density of protrusions and the minimum transmission rate of the low-energy heavy ions can be obtained. The detection efficiency of the new method for low-energy heavy ions was about 0.1-1 and the background in the measurement can be reduced to as low as 1.0 x 10(8) protrusions/cm2. With this method, the penetration depth of the energetic particles was detected to be no less than 60 micrometers in kidney bean slices when the slices were irradiated by 100 keVAr+ ion at the fluence of 5 x 10(16) ions/cm2.     

Swift heavy ion beam mixing at V/Si interface

Vanadium silicides are of increasing interest because of applications in high temperature superconductivity and in microelectronics as contact materials due to their good electrical conductivity. In the present work ion beam induced mixing at Si/V/Si interface has been investigated using 120 MeV Au ions at 1 × 10¹³ to 1 × 10¹⁴ ions/cm² fluence at room temperature. V/Si interface was characterized by Grazing Incidence X-Ray Diffraction (GIXRD), Atomic Force Microscopy (AFM), Rutherford Backscattering Spectrometry (RBS) and Cross-sectional Transmission Electron Microscopy (XTEM) techniques before and after irradiation. It was found that the atomic mixing width increases with ion fluence. GIXRD and RBS investigations confirm the formation of V₆Si₅ silicide phase at the interface at the highest ion irradiation dose.     

Partial crystallization of an amorphous alloy by electronic energy deposition

The first experimental evidence is reported of crystallization induced in an amorphous alloy by a high density of electronic excitation deposited along the path of swift heavy ions. The formation of nanocrystalline iron boride phases was observed in an amorphous Fe73.5Cu1Nb3Si13.5B9 alloy irradiated at low temperature with 5 GeV Pb ions up to fluences of 1 x 10(11) ions cm-2. No evidence for the formation of the Fe(Si) phase was found. This phenomenon was interpreted in terms of the relaxation of the high level of energy deposited in electronic excitations along the path of Pb ions in the target, which induces extensive stress and strain that could destabilize the amorphous structure.