Exploring reciprocity as a tool in low-energy electronic stopping

A computer code has been developed to explore reciprocity, i.e. the equivalence of electronic stopping cross sections for the ion-target pair A in B with that for B in A in the regime around and below the Bohr speed. With the aim of establishing reciprocity as a tool for identifying reliable experimental data and interpolating between them, we have studied stopping cross sections involving carbon, aluminium and gold either as projectile ions or as target materials. The case of carbon - where numerous data are available - is used to illustrate in detail various options to establish a body of credible data. Aluminium and gold serve to illustrate the case where these elements mostly are found as target materials in available data.     

Dependence of electronic stopping powers on incident ions using new Firsov formula

The dependence of the electronic stopping powers on the incident ions of the atomic number Z₁ in the materials of carbon, aluminum, nickel, silver and gold has been evaluated by using the new Firsov formula included the Sugiyama potential for the Firsov model and the screening length with the shell effect of electrons. It was found that the calculated results based on the new Firsov formula show the experimentally well-known Z₁-oscillation in the electronic stopping powers. The electronic stopping powers measured in carbon, aluminum, nickel and silver are reasonably reproduced by the new Firsov formula for the ZBL potential.     

Finite element analysis of ion-implanted diamond surface swelling

We present experimental results and numerical finite element analysis to describe surface swelling due to the creation of buried graphite-like inclusions in diamond substrates subjected to MeV ion implantation. Numerical predictions are compared to experimental data for MeV proton and helium implantations, performed with scanning ion microbeams. Swelling values are measured with white-light interferometric profilometry in both cases. Simulations are based on a model which accounts for the through-the-thickness variation of mechanical parameters in the material, as a function of ion type, fluence and energy. Surface deformation profiles and internal stress distributions are analyzed and numerical results are seen to adequately fit experimental data. Results allow us to draw conclusions on structural damage mechanisms in diamond for different MeV ion implantations.     

Modification of N-doped carbon induced by 30 MeV C60 ions

In the present work, 120 keV N-ion doped and 30 MeV C₆₀ ion irradiated graphite-like-carbon samples were characterized by RBS, micro-FTIR, micro-Raman, XPS spectroscopy and the variation of the properties of the samples with the N-dopant and/or C₆₀ irradiation fluence have been studied. The RBS spectra showed that C₆₀ irradiation can induce a partial diffusion of N atoms to the surface and the amount of the diffused N atoms increases slightly with increasing C₆₀ irradiation fluence. The FTIR and Raman spectra exhibit characteristic bands of carbon nitrogen bonds showing that the C and N atoms are chemically bonded. The amount of chemically bonded C and N atoms increases with increasing N-dopant. By deconvolution of the XPS spectra, the atomic concentration of N and C atoms were obtained and it was identified that the samples mainly consist of three phases, namely, C₃N₄, CN_x and tetrahedral amorphous carbon. The effect of N-dopant and C₆₀ irradiation fluence on the modification of the properties of the samples is also discussed.     

Focused ion beam fabrication and IBIC characterization of a diamond detector with buried electrodes

This paper reports on the fabrication and characterization of a high purity monocrystalline diamond detector with buried electrodes realized by the selective damage induced by a focused 6 MeV carbon ion beam scanned over a pattern defined at the micrometric scale. A suitable variable-thickness mask was deposited on the diamond surface in order to modulate the penetration depth of the ions and to shallow the damage profile toward the surface. After the irradiation, the sample was annealed at high temperature in order to promote the conversion to the graphitic phase of the end-of range regions which experienced an ion-induced damage exceeding the damage threshold, while recovering the sub-threshold damaged regions to the highly resistive diamond phase. This process provided conductive graphitic electrodes embedded in the insulating diamond matrix; the presence of the variable-thickness mask made the terminations of the channels emerging at the diamond surface and available to be connected to an external electronic circuit. In order to evaluate the quality of this novel microfabrication procedure based on direct ion writing, we performed frontal Ion Beam Induced Charge (IBIC) measurements by raster scanning focused MeV ion beams onto the diamond surface. Charge collection efficiency (CCE) maps were measured at different bias voltages. The interpretation of such maps was based on the Shockley-Ramo-Gunn formalism.     

The characterization of low energy molecular hydrogen ion—induced defects in synthetic diamond by optical absorption

The results of optical absorption analysis of the synthetic diamonds(type Ib) which were implanted with 40 keV molecular hydrogen ions at doses of 10^15-10^17H/cm^2(at 100K),showed that the increase of optical density(OD) of modified layer(-140nm) in UV-VIS region was dependent upon the damage level caused by ion implantation process.The range of relative optical band gap(Er.opt) around 2.0eV suggested that an amorphous carbon network structure like a-C film,which probably contains some localized subtetrabedral-coordinated clusters embedded in the fourflod(sp^3) sites.was tentatively found in this layer,basing on the optical gap of carbon materials.The evolution of Er,opt with ion fluence indicated that no more hydrogenated carbon compositions were produced in as -implanted samples,while the increase of Er,opt with annealing temperature was very similar to that of hydrogen content dependence of Eopt in hydrogenately amorphous carbon(a-C:H):In addition the optical inhomogeneity of type Ib diamond has been revealed by a 2-dimension topograph in transmission mode at λ=430nm。     

Ion implantation damage recovery in GaN

We present a method of ion implantation doping of GaN, which permits reduced residual damage. The method consists of performing implantation in several steps with annealing between each step. Residual damage was analyzed by RBS/channeling and compared to a traditional implantation and annealing procedure. Better lattice recovery is clearly achieved using the alternating implantation and annealing approach. We attribute the efficient recovery to smaller damage amounts introduced during each implantation step, as well as to suppression of secondary defect formation.     

低束流钕离子注入外延硅薄层的结构研究

采用金属蒸气真空弧（MEVVA）离子源以低束流方式将Nd离子注入到外延硅片中,经高温快速退火处理,制备了结晶良好的钕硅掺杂层。用扫描电子显微镜（SEM）、反射式高能电子衍射（RHEED）和X射线衍射（XRD）分析了在不同退火条件下样品注入层相结构的变化。研究结果表明,经高温热处理,注入层形成结晶良好的钕硅化合物,出现由Nd5Si4相向NdSi相转变的趋势。并对其转变过程进行了初步探讨。     

Pb离子辐照注碳a-SiO2薄膜的光致发光性能

用湿氧化法在单晶硅表面生长了非晶态SiO2薄膜,进行120 keV C离子注入和950 MeV Pb离子辐照,用荧光光谱分析样品发光特性的改变.结果发现,C离子注入和高能Pb离子辐照均能显著影响样品的发光特性,且荧光光谱的改变强烈依赖于注入和辐照剂量,预示不同注入和辐照剂量将导致不同的发光结构形成.对注入和辐照造成薄膜...     

金刚石薄膜为掩膜离子束室温溅射可控制备硅纳米圆锥阵列

以金刚石薄膜为掩膜,采用低能Ar+室温倾角溅射的方法制备密度和形貌可控的硅纳米圆锥阵列.扫描电子显微镜(SEM)结果表明,离子束溅射后得到的硅纳米圆锥密度与作为掩膜的金刚石薄膜颗粒密度相当;硅纳米圆锥的形貌与离子束入射角有密切关系,随着入射倾角由30°增大到75°;得到的硅纳米圆锥的锥角由73°减小到23°,其长径比从500 am/360 nm增大到2400nm/600nm.由于金刚石比硅材料的溅射速率更低,因此以金刚石薄膜为掩膜可以制备较大长径比的硅纳米圆锥阵列;随着入射角的增大,离子束溅射诱导的表面原子有效扩散系数减小和溅射速率增大是硅纳米圆锥的锥角减小、长径比增大的主要原因.     

Simulation of damage induced by ion implantation in Lithium Niobate

A simulation tool has been developed to engineer the damage formation in Lithium Niobate by ion irradiation with any atomic number and energy. Both nuclear and electronic processes were considered and, in particular, the dependence on the ion velocity of the electronic excitation damage efficiency has been taken into account. By using this tool it is possible both to draw damage nomograms, useful to qualitatively foresee the result of a given process, and to perform reliable simulations of the defect depth profiles, as demonstrated by the good agreement with the experimental data available in the literature.     

Size dependent hcp-to-fcc transition temperature in Co nanoclusters obtained by ion implantation in silica

In this work we present in situ investigations on the increase of the hcp-to-fcc transition temperature for Co with respect to the bulk value (420 °C) when nanoclusters are considered. Starting from Co:SiO₂ composites obtained by ion implantation with average Co cluster size of about 5 nm, a transition temperature between 800 °C and 900 °C is found upon thermal annealing in vacuum by in situ transmission electron microscopy. Preliminary results on electron irradiation to promote the transition at lower temperatures are presented.     

In~+离子注入蓝宝石(α-A1_2O_3单晶)的表面改性研究

研究了＜０００１＜和＜１２１０＞晶向蓝宝石（α－Ａｌ２Ｏ３单晶）在注入３６０ｋｅＶ．１×１０￣１６ｃｍ￣－２或１００ｋｅＶ、６×１０￣１６ｃｍ￣－２的Ｉｎ￣＋后产生的损伤、注入层的性能变化和退火行为。实验结果表明，退火过程中损伤的恢复和Ｉｎ的分布与退火气氛有关：在１００ｋｅＶ、６×１０￣１６ｃｍ￣－２的Ｉｎ￣＋注入时，注入层电阻率降低了１０个量级，大小为６．８×１０￣３·ｃｍ，表面损伤层的显微硬度提高了９２％；在３６０ｋｅＶ，１×１０￣１６ｃｍ￣－２的Ｉｎ＋注入时，其表面损伤层的显微硬度提高了４５％，在空气中不同温度下退火后，其显微硬度的变化和损伤的变化具有相同的规律。     

Initial damage processes for diamond film exposure to hydrogen plasma

Diamond is considered to be a possible alternative to other carbon based materials as a plasma facing material in nuclear fusion devices due to its high thermal conductivity and resistance to chemical erosion. In this work CVD diamond films were exposed to hydrogen plasma in the MAGnetized Plasma Interaction Experiment (MAGPIE): a linear plasma device at the Australian National University which simulates plasma conditions relevant to nuclear fusion. Various negative sample stage biases of magnitude less than 500 V were applied to control the energies of impinging ions. Characterisation results from SEM, Raman spectroscopy and ERDA are presented. No measureable quantity of hydrogen retention was observed, this is either due to no incorporation of hydrogen into the diamond structure or due to initial incorporation as a hydrocarbon followed by subsequent etching back into the plasma. A model is presented for the initial stages of diamond erosion in fusion relevant hydrogen plasma that involves chemical erosion of non-diamond material from the surface by hydrogen radicals and damage to the subsurface region from energetic hydrogen ions. These results show that the initial damage processes in this plasma regime are comparable to previous studies of the fundamental processes as reported for less extreme plasma such as in the development of diamond films.     

碳团簇Cn+(n=1-5)注入CR39树脂的吸收光谱研究

利用2×1.7串列加速器产生的团簇离子Cn+(n=l-5)注入到CR39树脂中,树脂的光吸收性质因注入的团簇离子的剂量、剂量率以及团簇中所含原子的个数不同而有不同的变化.该项研究表明团簇与固体相互作用时团簇效应是通过电子阻止来体现的.