Modelling of deposition processes on the TiO2 rutile (1 1 0) surface

Deposition of Ti_xO_y clusters onto the rutile TiO₂ (1 1 0) surface has been modelled using empirical potential based molecular dynamics. Deposition energies in the range 10-40 eV have been considered so as to model typical deposition energies of magnetron sputtering. Defects formed as a function of both the deposition energy and deposition species have been studied.The results show that in the majority of cases Ti interstitial atoms are formed, irrespective of whether Ti was contained within the deposited cluster. Furthermore that the majority of these interstitials are formed by displacing a surface Ti atom into the interstitial site. O surface atoms are also relatively common, with Ti and TiO₂ surface units often occurring when the deposited cluster contains Ti but becoming less frequent as the deposition energy is increased. Structures that would give rise to the growth of further layers of rutile are not observed and in the majority of the simulations the energy barriers for diffusion of the end-products is high.     

Evaluation of radiation environment in the target area of fragment separator HFRS at HIAF

In this work, the radiation environment in the target area of a fragment separator is evaluated using FLUKA code. The energy deposition in quadrupole coils is presented to provide guidance for a radiation-resistant magnets design. Results show that neutrons dominate in the prompt radiation field. A compact shielding design is recommended for high radiation areas along with the minimization of air activation in the tunnel in order to minimize the radiation effect on nearby beam lines. The displacements per atom results for the graphite target and copper coils indicate that the effect is insignificant. In addition, the activation level of the target is estimated for workers under possible hands-on maintenance condition.     

Cross-section for D(p,p)D elastic scattering from 1.8 to 3.2 MeV at the laboratory angles of 155° and 165°

The D(p,p)D cross-sections for elastic scattering of proton on deuterium over incident proton energy range from 1.8 to 3.2 MeV at both laboratory angles of 155° and 165° were measured. A thin solid state target Ni/TiD_x/Ta/Al used for cross-section measurement was fabricated by firstly depositing layers of Ta, Ti and Ni film on the Al foil substrate of about 7 μm in turn using magnetron sputtering and then deuterating under the deuterium atmosphere. The areal density of metal element in each layer of film was measured with RBS analysis by using a 4.0 MeV ⁴He ion beam, while the areal density of the deuterium absorbed in the Ti film was measured with ERD analysis by using a 6.0 MeV ¹⁶O ion beam. The results show that the cross-sections of p-D scattering under this experimental circumstance were much enhanced over the Rutherford cross-section value. It was found that the enhancement increases linearly as the energy of the incident beam increases. The total uncertainty in the measurements was less than 7.5%.     

贮氢金属多层膜制备技术及吸氢性能研究

研究了用电子束蒸发方法在Mo底衬上制备Ti-Ni复合膜和在SiO2底衬上制备Mo-Ti-Ni复合膜的方法,用离子束分析方法测量了各膜层的厚度,并对样品的吸氢性能进行了分析。研究发现,Ti膜表面镀Ni后,其吸氢温度降低,吸氢总量增加,表明其吸氢活性增强;Mo-Ti-Ni复合膜在Ti氢化后与SiO2底衬结合良好,并具有较高的强度,但这种膜对底衬的清洁度要求更高;50nm的Ti膜难以吸氢,原因可能是膜制备过程中温度过高,导致Mo-Ti-Ni之间扩散加深,形成相对过厚的过渡层,这还需进一步研究。     

Reactive DC Magnetron Sputter Deposited Titanium-Copper-Nitrogen Nano-Composite Thin Films with an Argon/Nitrogen Gas Mixture

A sintered Ti13Cu87 target was sputtered by reactive direct current (DC) magnetron sputtering with a gas mixture of argon/nitrogen for different sputtering powers. Titanium-copper-nitrogen thin films were deposited on Si (111), glass slide and potassium bromide (KBr) substrates. Phase analysis and structural properties of titanium-copper-nitrogen thin films were studied by X-ray diffraction (XRD). The chemical bonding was characterized by Fourier transform infrared (FTIR) spectroscopy. The results from XRD show that the observed phases are nano-crystallite cubic anti rhenium oxide (anti ReO3) structures of titanium doped Cu3N (Ti:Cu3N) and nano-crystallite face centered cubic (fcc) structures of copper. Scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDX) were used to determine the film morphology and atomic titanium/copper ratio, respectively. The films possess continuous and agglomerated structure with an atomic titanium/copper ratio ( 0.07) below that of the original target ( 0.15). The transmittance spectra of the composite films were measured in the range of 360 to 1100 nm. Film thickness, refractive index and extinction coefficient were extracted from the measured transmittance using a reverse engineering method. In the visible range, the higher absorption coefficient of the films prepared at lower sputtering power indicates more nitrification in comparison to those prepared at higher sputtering power. This is consistent with the formation of larger Ti:Cu3N crystallites at lower sputtering power. The deposition rate vs. sputtering power shows an abrupt transition from metallic mode to poisoned mode. A complicated behavior of the films’ resistivity upon sputtering power is shown.     

钇离子束动态增强沉积氮化钛膜

在膜层上接收注入钇离子和沉积钛原子比例Y^ :Ti=1:2的条件下，采用钇离子束动态增强沉积方法，在纯铁等基体上制备氮化钛膜层试样。对试样予以电化学测试和AES、XRD分析。XRD结果未发现钇单质或氮化钇的衍射峰。载能金属离子的动态增强沉积作用产生了界面混合效果，形成较宽的过渡层。动态增强沉积试样比非增强沉积试样有更强的抗电化学腐蚀能力。     

低能高束流氩离子源的结构及性能

离子源技术是等离子体研究中的一项重要内容,而低能大束流源则是离子源技术研究中的一个重要方向,因为这样的源在离子束刻蚀、离子束溅射镀膜以及荷能粒子与物质相互作用方面都有广泛的应用;本文采用空心阴极空心阳极结构,用热阴极电子发射弧放电驱动并用磁场约束产生等离子体,用曲面发射引出离子束,研制成了氩气放电溅射离子源;研究了灯丝加热电流、弧压对弧流的影响和弧流与工作气体压力对离子束引出的影响规律.离子源的引出电压在0-4.0 kV之间连续可调,最大引出束流为100 mA,束斑面积为φ6.0 cm,以Ti为溅射靶时的最大溅射沉积率为0.45 nm/s,离子源可连续工作160 h.     

RBS study of Ti/ZnO interface

We have studied the interface stability of the Ti(overlayer)/ZnO(substrate) system. Ti thin film was grown on the Zn face of single crystal ZnO(0 0 0 1) substrate by the vacuum deposition technique. The Ti film thickness was typically 16 nm. Then the samples were annealed in air at 300 and 400 °C for 15 min, respectively. The deposition and annealing effects on the interface structure were investigated with Rutherford backscattering and channeling spectroscopy using 2 MeV He⁺ ion beam. After Ti deposition the minimum yield from the ZnO substrate increased from 2% to 7%. This suggests severe damage caused by deposition, i.e. the interface reaction between Ti and ZnO (even at room temperature). A significant amount of Zn (approximately 6.4 × 10¹⁶ atoms/cm²) moved onto the surface after post-annealing at 400 °C. Since Ti has a stronger tendency to react with O than Zn, it is expected that Ti reacts with substrate oxygen leaving behind free Zn atoms, which can easily migrate onto the surface. We discuss how the Ti/ZnO interface reaction in detail, and seek to find another good metallic contact for ZnO devices, which are attracting much attention recently for practical applications as well as scientific aspects.     

强流脉冲离子束辐照对钛合金表面相结构的影响

利用X射线衍射(XRD)和能量色散的特征X射线谱(XEDS)扫描,对强脉冲离子束辐照钛合金的表面结构特征和成分分布进行了测试与分析。结果表明,试样钛合金为(α+β)型两相钛合金。当以低能流密度离子束辐照时,材料表面粗糙度的增加导致结构发生明显变化;随着离子束能流密度的增加,材料表面层出现微小非晶相;表面元素呈明显的层状均匀分布;多次脉冲离子束辐照下,表面形成Al2O3等氧化物,从而利于被辐照表面抗氧化性的提高。进一步提高离子束能流密度,多次脉冲辐照,材料表面形成了新相Al6MoTi和AlMoTi2。     

直流磁控溅射钛及钛合金薄膜的性能研究

用直流磁控溅射的方法在Si及Mo基片上制取Ti及其Ti合金薄膜。研究了基片温度等镀膜工艺参数对薄膜性能的影响,并用XPS、XRD、SEM分析薄膜的化学组成和结构特征,对薄膜的生长模式进行分析。结果表明,合金的加入降低了晶粒尺寸;升高温度可增大薄膜晶粒尺寸,改善薄膜结合能力;合金膜的成分与靶材基本一致。     

正电子致电离截面实验中束流强度的在线测量

本文采用HPGe探测器实时收集了正电子碰撞厚Ti靶伴随产生的湮灭光子,并结合HPGe探测器对放置在碰撞点处²²Na标准源产生的511 keV湮灭光子的探测效率刻度值,得到了8~9.5 keV正电子引起Ti原子内壳层电离截面实验中正电子束流强度的实时测量结果。结果表明,在实验测量的38 h内,基于²²Na标准源慢正电子束流装置产生的正电子束流强度不稳定,随时间的变化有着不同程度的衰减,且存在小幅度波动现象。因此,低能正电子致原子内壳层电离截面实验中应采用在线法获取慢正电子束流强度。     

计算脉冲电子束辐照下能量沉积剖面的新方案

脉冲电子束辐照材料试验研究中,束流电子具有不同的速度和角度分布。但数值模拟计算一般都考虑电子束垂直入射靶材料,这可能导致数值计算结果与试验结果不符。针对该问题,提出了一种计算电子束辐照下能量沉积剖面的新方案,利用MCNP(Monte Carlo N Particle Transport Code)软件对铝、铜、钽金属材料在电子束辐照下的能量沉积进行模拟,分析了电子束垂直入射与带有角度分布入射时能量沉积的差异,为解释电子束辐照试验测量数据与理论计算结果之间的差异提供了依据。     

MoS2/Ti multilayer deposited on 2Cr13 substrate by PIIID

Plasma immersion ion implantation and deposition (PIIID) was used to fabricate the MoS₂/Ti multilayer on the 2Cr13 substrate. The Ti layer was deposited by a pulse cathodic arc plasma source and the MoS₂ layer was obtained by a radio-frequency (RF) magnetron sputtering system. Scanning electron microscope (SEM), ball-on-disk, electrochemical and water vapour spray tests were used to characterize the as-deposited multilayer. The SEM result shows that the MoS₂/Ti multilayer has formed a good layered structure. The friction curves of MoS₂/Ti multilayers reveal that the wear resistance and friction coefficient of the multilayer can be improved significantly by a proper structure. The anode polarization curves obtained in 0.5% H₂SO₄ solution show that the corrosion current density of the MoS₂/Ti multilayer can be decreased to 68% of that of the MoS₂ single layer. In addition, results of the water vapour spray test for 48 h show that the surface of the MoS₂/Ti multilayer is smooth and no erosion can be found, where the MoS₂ single layer is partially peeled off from the substrate.     

Improved Design of Beam Tunnel for 42 GHz Gyrotron

In gyrotron, there is the chance of generation and excitation of unwanted RF modes (parasite oscillations). These modes may interact with electron beam and consequently degrade the beam quality. This paper presents the improved design of the beam tunnel to reduce the parasite oscillations and the effect of beam tunnel geometry on the electron beam parameters. The design optimization of the beam tunnel has been done with the help of 3-D simulation software CST-Microwave Studio and the effect of beam tunnel geometry on the electron beam parameters has been analyzed by EGUN code.     

用LAHET和MCNP程序研究散裂中子靶的中子学性能

利用LAHET和MCNP程序对ADS散裂中子靶进行模拟计算。因靶的基本物理性质随束流和靶形状的变化而改变,所以首先评估了源强和靶的几何形状对靶性质的可能影响,然后计算长1.2m、直径为0.6m的圆柱形液态铅靶在1GeV质子轰击下,靶内中子的产生和泄漏及能量的沉积等。与文献数据、实验数据进行了比较,符合良好。计算结果还表明:源强和几何的选择对中子产生和泄漏可产生较大影响;用液态铅作散裂靶时,中子产额和泄漏额较高,且泄漏能谱在可利用范围内,但能量沉积在靶中的分布极不均匀,这可能给传热带来问题。     

在电子驻波直线加速器上获得小束斑电子束

近年来高效率探测器阵列数字辐射照相技术已经用于无损探伤实时在线图象处理检测。厚在则重的关键部位的微小缺陷，需要用加速器产生的高能电子束作为焦点打靶产生Ｘ射线进行无损探伤检测。     

Simulation of Multigroup X-Ray,Alpha-Particle and Neutron Transport in Ion Beam Driven ICF Target

A one-dimensional Lagrangian code, MEDUSA-IB for the analysis of ion beam fusion target behavior was developed. The code included multigroup X-ray, α-particle and neutron transport models. Photon transport equation was solved by variable Eddington method. Particle tracking method and collision probability method were used for the simulation of α-particle and neutron transport respectively. Temperature dependent ion beam energy deposition was also considered. Each routine of the code was verified separately. The analysis of a bare 1 mg DT target after ignition showed that only neutron transport slightly decreases fusion yield. The analysis of a reactor-size hollow single shell target containing 4.2 mg DT fuel, UTLIF target showed: Radiation and α-particle transport, temperature dependence of ion beam stopping and the equation of states decreased fusion gain when they were considered accurately. Neutron transport slightly increased the gain. The momentum deposition of ion beam and α-particles had very slight effects.     

Recent Developments in Magnetron Sputtering

The principle of magnetron sputtering is introduced andthe balanced and unbalanced magnetrons are compared andthe necessity of unbalanced magnetrons is explained as well. Several recent developments in plasma magnetron sputtering, i.e., unbalanced magnetron sputtering, pulsed magnetron sputtering and ion assisted sputtering, are discussed. The recent developments of unbalanced magnetron systems and their incorporation with ion sources result in an understanding in growingimportance of the magnetron sputtering technology, which makes the technology an applicable deposition process for a variety of important films, such as wear-resistant films and decorative films.     

A fully three-dimensional reconstruction algorithm with thenonstationary filter for improved single-orbit cone beam SPECT

Conventional single-orbit cone beam tomography suffers from incomplete sampling and an inadequate three-dimensional (3D) reconstruction algorithm. The commonly used Feldkamp reconstruction algorithm simply extends the two-dimensional (2D) fan beam algorithm to 3D cone beam geometry. A truly 3D reconstruction formulation based on the 3D Fourier slice theorem is derived for a single-orbit cone beam SPECT. In the formulation, a nonstationary filter which depends on the distance from the central plane of the cone beam is derived and applied to the 2D projection data in directions along and normal to the axis of rotation. This algorithm was evaluated using both computer simulation and experimental measurements. Significant improvement in image quality was demonstrated in terms of decreased artifacts and distortions in cone beam reconstructed images. However, compared with the Feldkamp algorithm, a fivefold increase in processing time is required     

PIXE measurements of Kr-sputtered TiN coatings

Titanium nitride films of 30–300 nm thickness deposited via dc magnetron sputtering were irradiated with 150–700 keV Kr ions at fluences up to 2.1 × 10¹⁷ cm⁻². These films were then scanned with a well-collimated 400 keV proton beam and the X-ray yield of Ti was measured both in and outside the Kr beam spot. This procedure results in a precision determination of the average film thickness (± 1% in the case of tens of nm films). The PIXE results are found to be consistent with RBS data of the same specimens. Sputtering yields were determined from the variation of X-ray yields assuming unchanged Ti/N stoichiometry in the implanted area. For thick TiN films (d₀ > 100 nm) the sputtering yields are in good agreement with predictions of the collisional cascade model by Sigmund. In contrast, sputtering of thin layers (d₀ = 30 nm) depended sensitively on the ion energy, being a factor of 2 higher at 150 keV than at 500 keV.