Refractive index change mechanisms in swift-heavy-ion-implanted Nd:YAG waveguide

A buried planar Nd:YAG waveguide has been fabricated by 20-MeV N-ion implantation. From Raman and optical characterization, it has been found that the refractive index has a larger increase when the crystal damage is heavier. According to our analysis, this crystal damage is caused by the electronic energy loss in the first several micrometers of irradiated regions, while nuclear energy loss also acts on the damage near the end of the ion range. This work is helpful to understand the mechanisms of swift-heavy-ion-implanted Nd:YAG waveguide formation.     

Cu2+离子注入的石英光波导的特性研究

利用Cu2+离子注入的方式在熔融石英和石英晶体上分别制备了平面光波导结构.通过棱镜耦合实验测试了两种光波导的导模特性,结果表明:在同样的注入条件下熔融石英上形成了增加型的光波导结构,而石英晶体上形成了位垒型的光波导结构.研究了退火温度对两种光波导导模折射率的影响,熔融石英光波导中导模的折射率随着退火温度的升高而降低,而石英晶体光波导中导模的折射率随着退火温度的升高先增加后降低.为了进一步分析离子注入两种材料形成光波导的微观机理,利用SRIM模拟了Cu2+离子注入两种材料的电子能量损失和核能量损失,并且模拟了两种光波导结构的折射率分布.模拟结果表明:熔融石英光波导的主要形成原因是离子注入表面的折射率大于其体材料的折射率,而石英晶体光波导的主要形成原因是离子射程末端的折射率小于其体材料的折射率.因此,在熔融石英光波导的形成中电子能量损失起主要作用,而在石英晶体光波导的形成中核能量损失起主要作用.     

Assessment of damage ranges by measurements of the refractive index in ion implanted LiNbO3 and LiTaO3

Ion implantation in LiNbO₃ and LiTaO₃ produces radiation damage by nuclear collisions. The amorphisation of the lattice reduces the refractive index of the material. In the case of fast ion bombardment with helium this damage layer is buried below the surface. The refractive index profile which then exists is suitable for an optical waveguide on the surface which supports several modes. Analysis of the refractive index profile yields the damage distribution in the crystal and this in turn can be compared with theoretical estimates of the damage production and ion ranges.

Our analyses show that in the high energy range from 0.5 to 2.0 MeV the depth of the damage is predominantly controlled by the electronic stopping.     

Double optical waveguide in Cu-doped KNSBN crystal formed by MeV boron ion implantation

We reported for what is to be believed the first time a double optical waveguide in a Cu-doped potassium sodium strontium barium niobate (KNSBN) crystal formed by double boron ion implantation. The energy and dose of B⁺ and B³⁺ ions were (3+6) MeV and (2+2)×10¹⁴ ions/cm², respectively. The refractive index profile of the waveguide showed a double-barrier confined shape, which suggested the formation of a two-layer waveguide structure. The two waveguide layers were with thickness of 2.6 and 2 μm, respectively, which was in a good agreement with the parameters obtained from transport and range of ions in matter 98 (TRIM) code simulation. The nuclear energy loss distribution of the MeV B ions implanted into this crystal had a similar shape to that of the waveguide index profile, which means an inherent relationship between the waveguide formation and the energetic energy deposition.     

重离子辐照SiO2通过能量损失产生发光色心的研究

通过红外光谱和荧光发射光谱分别对600 keV、4 MeV和5 MeV Kr离子辐照的SiO2进行发光特性的研究。在低能量辐照体系中,简单色心(F2色心)的形成在损伤过程中占据主导地位,其主要诱发蓝光发射带;在高能离子辐照条件下,离子径迹上的能量密度较大,因此缺陷浓度的增大产生了一些缺陷团簇和离子径迹,形成了复杂的色心(F2+和F3+色心等)并诱发了强烈的绿光发射带和红光发射带。该实验结果与能量损失过程中统一热峰理论模型(一个综合的基于电子能损与核能损的非弹性碰撞模型和弹性碰撞模型)的模拟结果能够很好地吻合,表明在keV～MeV能区上存在电子能损过程与核能损过程的协同效应。     

Molecular dynamic simulation of secondary ion emission from an Al sample bombarded with MeV heavy ions

Spluttering yields and kinetic energy distributions (KED) of Al atomic ions ejected from a pure aluminium sample under MeV silicon ion bombardment were simulated with the molecular dynamic method.Since the electronic energy loss Se is much higher than the nuclear energy loss Sn when the incident ion energy is as high as several MeV,the Se effect was also taken into consideration in the simulation.It was found that the simulated sputtering yield fits well with the experimental data and the electronic energy loss has a slight effect at incident ion energies higher than 4MeV.The simulated secondary ion KED spectrum is a little lower in the peak energy and narrower in the peak width than that in the experiment.     

Formation of optical waveguide in KNSBN crystal by low dose MeV H-ion implantation

The first H-ion implanted Cu-doped (K_0.5Na_0.5)_0.2(Sr_0.75Ba_0.25)_0.9Nb₂O₆ crystal planar waveguide is reported in this paper. Low dose MeV H ion implantation into a crystal of KNSBN has been used to fabricate the waveguide by generating a buried layer of lowered refractive index. Both TE and TM modes are observed. The reconstructed refractive index profiles in the waveguide are obtained using a parametrized index profile reconstruction method. The simulated results of TRIM show that the nuclear collision influences most the ordinary index profile, but in the region of the guide the extraordinary index profile may be related to the electronic energy loss.     

快重离子辐照C60薄膜的强电子激发效应研究

利用能量为2.0GeV的¹³⁶Xe和2.7GeV的²³⁸U离子对C₆₀薄膜进行了辐照,并用傅立叶变换红外光谱、X射线衍射谱和拉曼散射技术分析了辐照过的C₆₀样品,在傅立叶变换红外光谱上,首次观察到一个位于670cm^－1处的,表征未知结构的新峰,研究了其强度随电子能损和辐照剂量的变化规律.分析结果表明,电子能量转移主导了C₆₀薄膜的损伤过程;而损伤的部分恢复是由强电子激发的退火效应引起的;另外,离子的速度在损伤的建立过程中也起了一定的作用     

On generation of electromagnetic waves in the terahertz frequency range in a multilayered open dielectric waveguide

We show that it is possible to produce terahertz wave generation in an open waveguide, which includes a multilayer dielectric plate. The plate consists of two dielectric layers with a corrugated interface. Electrons, drifting in the potential well, interact with the non-uniform electric field which is induced near the dielectric interface by the natural wave of the waveguide. The corrugated period and parameters of the electronic system are chosen in order to ensure the most effective interaction of electrons with a wave. Generation of electromagnetic waves is achieved by converting the electrons? energy into the electromagnetic wave energy.     

金属材料中高能重离子辐照效应的理论描述

简要介绍了高能重离子在金属材料中引起辐照效应的主要理论 ,特别是与电子能损引起的缺陷产生与演化、离子潜径迹形成、辐照相变以及各向异性塑性形变等效应相应的理论描述.Experimental results showed that, for high energy heavy ion irradiations, electronic energy loss could play a dominant role in damage process in solid materials. In order to explain the experimental phenomena and results, a series of theoretical models based on Coulomb explosion or thermal spike mechanisms have been proposed. In the present paper, more attention was paid to theoretical expressions of high energy heavy ion irradiation induced effects in metallic materials ...     

Conductivity of irradiated Kapton in relation to energy loss of ions and electrons

Abstract

We have studied the effects of 2.5 MeV electron irradiation and ion (C, N, F, Si and Kr) bombardment on the electrical conductivity of a polyimide (Kapton-H) with ion energies ranging between 320 keV (N) and 1.25 GeV (Kr). In this wide range of situations we have tried to sort out the respective effects of nuclear and electronic excitation energy losses.

For all ion irradiation the conductivity is found to scale with the electronic excitation absorbed dose: i.e. a power law of conductivity versus absorbed dose with an exponent around 9 is observed. At a given absorbed dose (in Gray units) the efficiency of each ion to enhance conductivity is found to be proportional to the electronic energy loss; electrons are much less efficient than ions and thus collective excitations are required to achieve this process.

The nuclear energy loss can perhaps play some role at conductivities higher than 100 Ω^?1 m^?1, but its effects are negligible in the range explored here.     

用离子辐照模拟研究反应堆结构材料中金属/金属界面原子扩散行为

介绍了利用载能离子辐照模拟研究反应堆结构材料中金属／金属界面原子扩散行为的实验进展,特别是辐照参数（如辐照剂量、辐照温度、核能损、电子能损以及膜结构等）对界面原子扩散行为的影响,并对可能的机理进行了简要的评述。 Atom diffusion at metal/metal interfaces is very important for property of reactor structural materials, which can be simulated by using energetic ion irradiations. The present situation of experimental studies on atom diffusion at metal/metal interfaces induced by energetic ion irradiations is reviewed. The influence of experimental parameters such as the irradiation dose, irradiation temperature, electronic energy loss, nuclear energy loss and the interface structure on the intermixing is emphatically introduced. In addition, the possible mechanisms of metal/ metal intermixing are also briefly described.     

Ranges and standard deviations of implanted ions

This paper presents a theoretical analysis and simple expressions for the calculation of ranges and standard deviations of implanted ions in amorphous targets. Nuclear energy loss models are discussed to introduce an approximation formula for the nuclear stopping cross section appropriate for Thomas-Fermi, Lenz-Jensen and intermediate type potentials. The Firsov electronic stopping model has been used to show its successful application. Algebraical expressions for the total range of ions in monoatomic and biatomic targets as a function of ion energy result from the considerations presented. A quasi-elastic multiscattering model is suggested, which permits an easy estimate of projected ion ranges. The standard range deviation is obtained by determining the total average-square energy loss fluctuations. Finally a comparison of calculated and experimental results is made to show that calculations based on the Firsov electronic stopping model and the nuclear stopping cross section proposed here provide a better agreement with the experimental results than the wellknown Johnson-Gibbons LSS-calculations.     

加速器束流脉冲化及氢二次离子发射研究

详细介绍了快速高压晶体管开关在加速器束流脉冲化和用于二次离子测量的加速器飞行时间谱仪上的应用. 利用飞行时间法研究了碳纳米管在不同能量的Si和Si2团簇离子轰击下氢二次离子的发射. 实验结果表明， 在每个原子质量单位的速度为2.5×108 cm/s以上， Si和Si2离子引起的氢二次离子的发射主要受电子阻止过程控制； 在每个原子质量单位的速度为2.5×108 cm/s以下和Si2团簇离子轰击的情况下， 氢二次离子的发射产额明显增加， 团簇离子在靶表面的核能损增强效应起主要作用. The application of Fast High Voltage Transistor Switches (HTS) in pulsed ion beam and the time of flight(TOF ) setup is described. Secondary ion emissions from carbon nanotubes under bombardments of MeV Si and Si2 clusters are measured by using TOF. The measurements indicate that the yield of the secondary ion emissions of hydrogen increases with increasing energy of Si and it is attributed to the electronic processes. The yield of the secondary ions of hydrogen decreases with increasing energy of Si2 clusters and the enhancement of nuclear energy loss of cluster constituents at the surface of sample plays a more significant role in the secondary ion emission of hydrogen at the low energies.     

Ejection of H2O,O2, H2 and H from water ice by 0.5–6 keV H+ and Ne+ ion bombardment

The ejection of H₂O, O₂, H₂ and H from water ice at 30–140 K, bombarded by 0.5–6 keV H⁺ and Ne⁺ was studied experimentally. Neon ions in this energy range deposit their energy in the ice by nuclear collisions, whereas with protons of 0.5 to 6 keV the energy deposition mechanism shifts gradually from predominantly nuclear collisions to predominantly electronic processes. The existing theory of nuclear sputtering predicts very well the yield of ejected water molecules and the experimental results in the region of electronic processes agree well with the experimental results of Lanzerotti, Brown and Johnson. However, the major mass loss from water by ion bombardment is via the ejection of O₂, H₂ and H atoms, which exceed the ejection of water molecules. O₂ and H₂ production is markedly enhanced at temperatures exceeding ~100 K, whereas H₂O and H production are temperature independent, suggesting that O₂ and H₂ are produced in the bulk of the ice whereas H₂O and H atoms are ejected from the surface or near surface layers.     

GeV能量的Fe离子在C60薄膜中的辐照效应研究

利用傅立叶转换红外光谱和Raman谱仪分析了0.98 GeV的Fe离子在电子能损Se为3.5 keV/nm时， 不同辐照剂量（5×1010 —8×1013 ions/cm2)下， 在C60薄膜中引起的辐照损伤效应。 分析表明， Fe离子辐照引起了C60分子的聚合与损伤。 在辐照剂量达到一中间值1×1012 ions/cm2， C60分子的损伤得到部分恢复， 归因于电子激发引起的退火效应。 通过对Raman数据的拟合分析， 演绎出Fe离子辐照在C60材料中形成的潜径迹截面或引起损伤的截面约为1.32×10-14 cm2。     

Waveguide effect in ZnO crystal by He+ ions implantation: Analysis of optical confinement from implant-induced lattice damage

Waveguide effect was observed in He⁺ implantation ZnO with different energies and doses. Computer code was used to simulate the process of ion implantation into ZnO crystal and the implantation-produced damage distribution is extracted according to RBS experimental result. The prism coupling and end-face coupling technique are used to investigate the waveguide properties. The reconstructed refractive index profile shows that the ordinary index decreases at the near surface region after He⁺ implantation under different conditions. The damage layer, which is governed by nuclear energy deposition of He⁺ ions, makes itself a reduced index barrier for guiding light. Ion-implantation, generally used for electrical isolation, may play a role for optical confinement in ZnO light emitting devices.     

快重离子在凝聚态物质中引起的效应——电子能损效应

简述了快重离子在凝聚态物质中引起的效应——电子能损效应,主要包括缺陷的产生和潜径迹的形成、各向异性的塑性形变、由弹性碰撞产生的缺陷的部分退火、相变（非晶化）,以及尝试性的理论解释．     

高能铁离子在水介质中核反应过程所导致的能量沉积

在银河宇宙射线中,400MeV/nucleon的铁离子通量相对来讲是较高的,400MeV/nucleon的铁离子对空间辐射引起的损伤和辐射剂量有重要的贡献.本文以Geant4为基础,对400MeV/nucleon Fe离子与物质相互作用后通过核反应过程产生的次级碎片进行模拟分析.对铁离子在水中产生的能量沉积和铁离子与水介质发生核反应后产生的次级碎片的能量沉积进行了模拟研究,得到了通过核反应过程产生次级粒子所导致的剂量贡献. 关键词： 能量沉积 剂量 碎片     

Nanostructuring and hardening of LiF crystals irradiated with 3–15 MeV Au ions

Modifications of the structure and mechanical properties in LiF crystals irradiated with MeV-energy Au ions have been studied using nanoindentation, atomic force microscopy and optical spectroscopy. The nanostructuring of crystals under a high-fluence irradiation (above 10¹³ ions/cm²) was observed. Nanoindentation tests show a strong ion-induced increase of hardness (up to 150–200%), which is related to the high volume concentration of complex color centers, defect aggregates, dislocation loops and grain boundaries acting as strong barriers for dislocations. From the depth profiling of the hardness and energy loss it follows that both nuclear and electronic stopping mechanisms of MeV Au ions contribute to the creation of damage and hardening. Whereas the electronic stopping is dominating in the near-surface region, the effect of elastic displacements prevails in deeper layers close to the projectile range.