Swift heavy ion induced structural modifications in indium oxide films

Sub-stoichiometric indium oxide (In_xO_y) films were fabricated by electron-beam evaporation method. One set of films was irradiated with 120 MeV Ag⁹⁺ ions of varying fluences. Another set was thermally annealed and subsequently irradiated. Irradiation of the as-deposited In_xO_y films leads to a phase separation resulting in In and In₂O₃ and the formation of nanometer crystalline In clusters. The In cluster size is in the range of 35-45 nm. Elastic recoil detection analysis indicates a decrease in the O/In ratio with an increase in ion fluence, suggesting oxygen loss during irradiation. On the other hand, thermal annealing of the as-deposited In_xO_y films leads to a complete conversion into stoichiometric In₂O₃. The structure of the stoichiometric films is further resistant to irradiation. Preliminary electrical investigations indicate a decrease in the resistivity of the as-deposited sub-stoichiometric In_xO_y films with irradiation, but a very large increase after irradiation of the stoichiometric thermally annealed films. Thus, structural and electrical modifications induced by swift heavy ions depend upon the stoichiometry of the film.     

Incorporation of oxygen during oxidative annealing of thermally evaporated In films

The paper describes studies on compositional, morphological and optical characteristics of thin indium oxide films prepared by annealing thermally evaporated indium metal films in 423-723 K temperature range in air. The incorporation of oxygen in the films has been probed by depth profiling oxygen using ¹⁸O(p, α)¹⁵N nuclear reaction and 3.05 MeV ¹⁶O(α, α)¹⁶O resonant scattering. The morphology of the films has been examined by atomic force microscopy while their structure by glancing incidence X-ray diffraction. As grown In films are polycrystalline and consist of well-aligned (In) hillocks. The hillocks in thin films (∼12 nm) are nanosized and conical in shape while those in thicker films (∼130 nm) are micron-sized with rather flat tops. Nanosized hillocks impart films enhanced reactivity towards oxygen. Consequently thinner films contain high amount of adsorbed oxygen in as-deposited state and undergo facile oxidation. The hillocks are obliterated in the process. The enhanced reactivity is attributed to high surface energy, generally associated with nanoparticles, and residual stress. These films exhibit high transmission (>90%) on annealing beyond 473 K. Micro-sized hillocks, on the other hand lend pronounced roughness to the films. Roughness and lower surface free energy which manifests in the form of flatter hillock tops, make the films oxidation-resistant. Depth profile measurements in thicker films show that oxidation starts at the surface and proceeds into the interiors of the film with increase in the duration of annealing. The films are deficient in oxygen, even as X-ray diffraction shows the formation of polycrystalline indium oxide. These have low transmission (<30%) and their band gaps increase with the temperature and duration of annealing. The increase in band gap is attributed to the gradual oxidation of interior regions that are initially significantly deficient in oxygen and improvement in crystallinity.     

Effects of O swift heavy ion irradiation on indium oxide thin films

Indium oxide thin films deposited by spray pyrolysis were irradiated by 100 MeV O⁷⁺ ions with different fluences of 5 × 10¹¹, 1 × 10¹² and 1 × 10¹³ ions/cm². X-ray diffraction analysis confirmed the structure of indium oxide with cubic bixbyite. The strongest (2 2 2) orientation observed from the as-deposited films was shifted to (4 0 0) after irradiation. Furthermore, the intensity of the (4 0 0) orientation was decreased with increasing fluence together with an increase in (2 2 2) intensity. Films irradiated with maximum fluence exhibited an amorphous component. The mobility of the as-deposited indium oxide films was decreased from ∼78.9 to 43.0 cm²/V s, following irradiation. Films irradiated with a fluence of 5 × 10¹¹ ions/cm² showed a better combination of electrical properties, with a resistivity of 4.57 × 10⁻³ Ω cm, carrier concentration of 2.2 × 10¹⁹ cm⁻³ and mobility of 61.0 cm²/V s. The average transmittance obtained from the as-deposited films decreased from ∼81% to 72%, when irradiated with a fluence of 5 × 10¹¹ ions/cm². The surface microstructures confirmed that the irregularly shaped grains seen on the surface of the as-deposited films is modified as “radish-like” morphology when irradiated with a fluence of 5 × 10¹¹ ions/cm².     

Depth dependent lattice disorder and strain in Mn-implanted and post-annealed InAs thin films

The lattice order degree and the strain in as-grown, Mn-implanted and post-implanted annealed InAs thin films were investigated with depth resolution by means of Rutherford backscattering spectrometry in channeling conditions (RBS/C). Three main crystallographic axes were analyzed for both In and As sublattices. The behaviour of the induced defects was evaluated in two regions with different native defects: the interface and the surface. The results show that Mn implantation and post-implantation annealing are anisotropic processes, affecting in a different way the In and As sublattices. The mechanisms influencing the enhancement and deterioration of the crystal quality during the implantation are discussed in relation to the as-grown defects and the segregation of the elements.     

Characterization of silicon oxynitride films using ion beam analysis techniques

Heavy-ion elastic recoil detection analysis (HIERDA) is the ideal technique for quantitative analysis of silicon oxynitride films on silicon because of its unique ability to measure simultaneously all elements of interest (i.e., H, C, N, O and Si), thereby permitting key parameters such as the O/N-ratio to be determined in a single measurement. However, high-energy accelerators suitable for such HIERDA measurements are becoming much less readily available. Hence, the present paper investigates and calibrates an alternative IBA technique for simultaneous O, N and C analysis – namely, the use of (d,p) and (d,) nuclear reactions. Under optimum analysis conditions (850 keV deuterons and 150° detector angle), the Si background level sets a lower detection limit of 1×10¹⁶ nitrogen atoms/cm² and 3×10¹⁵ oxygen atoms/cm². H analysis is carried out separately, using low-energy ERDA and a 2 MeV ⁴He beam. Absolute cross-sections have been obtained for each of the (d,p) and (d,) groups. Comparison with data in the recent Handbook of Modern Ion Beam Materials Analysis shows reasonable agreement (10–15%) for the (d,p) reactions on oxygen and carbon. However, in the case of nitrogen, the measured cross-section values are 70% larger than the Handbook data. Several silicon oxynitride samples have been analyzed, first at UWO using 850 keV deuterons, and subsequently at ANU using HIERDA and a 200 MeV Au beam. The resulting O/N-ratios agree to within 10%. The relative importance of radiation damage effects is briefly discussed.     

Preparation and characterization of zirconium films for first mirror application in fusion devices

The nanostructured zirconium (Zr) films deposited on Al₂O₃ substrate are obtained by pulsed laser deposition (PLD) for the application of first mirror. Structural features, optical properties and surface morphologies of as-grown Zr films are systematically investigated as a function of pulse repetition rate. It is found that the Zr films show a typical hexagonal close packed structure and all deposited films exhibit a very smooth surface. There are no voids and folds on the surface of Zr films. The root mean square roughness (RMS) values increase with increasing pulse repetition rate. The variation of pulse repetition rate has no obvious effects on the reflectivity because of the smooth film surface. Up to the wavelength of 800 nm, the reflectivity is higher than 70%, which is excellent for the application of first mirror.     

Study of 200 MeV Ag ion induced amorphisation in nickel ferrite thin films

Thin films of nickel ferrite of thickness ∼100 and 150 nm were deposited by pulsed laser deposition. The films were irradiated with a 200 MeV Ag¹⁵⁺ beam of three fluences 1 × 10¹², 2 × 10¹² and 4 × 10¹² ions/cm². X-ray diffraction showed a decrease in the intensity of peaks indicating progressive amorphisation with increased irradiation fluence. Fourier transform infra-red and Raman spectra of pristine and irradiated films were also recorded which showed a degradation of the crystallinity of the samples after irradiation. The damage cross section of the infra-red bands was determined. It was found that the two bands at 557 and 614 cm⁻¹ did not show similar behaviour with fluence.     

Scanning X-ray microfluorescence in a SEM for the analysis of very thin overlayers

In this paper, we used back-foil scanning X-ray microfluorescence (SXRF) and we examined the sensitivity of the technique for the analysis of very thin overlayers, where electron probe X-ray microanalysis (EPMA) reaches its detection limits. The lateral resolution of back-foil SXRF is also calculated for all the systems used. Both experimental results and Monte-Carlo calculations are used in this respect. Back-foil SXRF used in optimized experimental conditions, is found to be more sensitive than EPMA, especially in the case of very thin overlayers. The lateral resolution of back-foil SXRF is of the order of some micrometers. This is much better than the lateral resolution in conventional XRF and of the same order of magnitude as in EPMA.     

Microstructure and properties of tungsten–samarium oxide composite prepared by a novel wet chemical method and spark plasma sintering

W–1 wt% Sm₂O₃ powders doped with highly uniform Sm₂O₃ were successfully synthesized by a novel wet chemical method followed by hydrogen reduction. The powders were consolidated by spark plasma sintering (SPS) at 1800 °C to suppress grain growth during sintering. The FE-SEM and HRTEM analysis, tensile test and thermal conductivity measurements were used to characterize these samples. The grain size, relative density of the bulk samples fabricated by SPS sintering were 4 μm and 97.8%, respectively. The tensile strength values of Sm₂O₃/W samples were higher than those of pure W samples. As the temperature rises from 25 to 800 °C, the thermal conductivity of pure W and W–1 wt% Sm₂O₃ composites decreased with the same trend and the thermal conductivity of both samples was above 160 W/m K at room temperature.     

Numerical analysis of MD events and preliminary thermal calculation for KTX vacuum vessel

KTX is a new reversed field pinch (RFP) magnetic confinement device which is under design in ASIPP and USTC. Major disruption (MD) events may occur in future operating process, which is simulated with the finite element (FE) method. The results present that the peaks of eddy currents on vessel and conductor shell are respectively 11.791 kA and 68.637 kA with maximum stress 67.1 MPa due to high transient electromagnetic (EM) force. It is confirmed that the structure is still strong enough to bear the electromagnetic loads even if the worst case. Besides, as KTX vacuum vessel will take the method of natural cooling for heat dissipation during plasma discharge (0.5–1.0 MA), a preliminary thermal calculation was implemented in normal condition to decide suitable time parameters such as duration and interval. It is suggested that the discharge interval should be no less than 5 min for the complete 1 MA plasma with 100 ms duration, which can guarantee the temperature of vacuum vessel below 200 °C.     

Ti离子注入SiO_2合成TiO_2纳米颗粒及其光学性质

将105 keV的Ti离子注入到SiO_2玻璃至1×10~(17)、2×10~(17) cm~(-2),并在氧气气氛下进行热处理,借助紫外可见分光光度计、掠入射X射线衍射光谱仪、透射电子显微镜、原子力显微镜等多种测试仪器,详细研究了Ti O2纳米颗粒的形成、结构、分布及其光吸收和催化性能。研究结果表明,高注量Ti离子注入结合氧气气氛热处理可以在SiO_2基底中形成TiO_2纳米颗粒,并以金红石相为主。合成的TiO_2纳米颗粒的形貌明显依赖于离子的注量,随离子注量增加,形状不规则且分散排列的TiO_2纳米颗粒会转变成尺寸较为均匀、分布致密的纳米颗粒,进而形成了TiO_2类颗粒膜结构。另外,光催化降解实验结果表明,合成的纳米颗粒对罗丹明B溶液具有一定的降解作用。     

Improvements in performance and microstructure of doped graphites as plasma-facing materials by a new process

Multi-elemental (B, Si and Ti) doped graphite was prepared from fillers of petroleum coke, dopants and binder of coal tar pitch by a new liquid mixing method. Such composite has not only high thermal conductivity (233 W/m K) but also excellent mechanical strength compared with the material prepared by the conventional solid mixing method. Scanning electron microscopy (SEM) results show that such material has a fine-grained structure as well as little pore diameter. The effects of the manufacturing procedure of doped graphites on the performance and microstructure are investigated. In addition, correlations between properties and microstructure are also discussed in detail.     

红外吸收法与热导法同时测定铀硅化合物中氧、氮含量

采用氧/氮分析仪对铀硅化合物中氧、氮含量的测定方法进行了研究,以红外吸收法和热导法测定了铀硅化合物中氧、氮的含量。考察了取样量、助熔剂、加热功率、分析时间等参数对氧、氮含量测定的影响,并优化了相关的工作参数。当取样量为0.10 g(准确至0.0001 g)时,在以镍篮为助熔剂、4200 W的加热功率条件下,氧的质量分数测定范围为0.00050%～0.365%,氮的质量分数测定范围为0.00050%～0.026%,线性相关系数均大于0.999,测定相对标准偏差均优于10%。     

反应堆脉冲中子和γ射线辐照SiGe HBT器件的退火因子及典型直流参数测量分析

本工作测量了反应堆脉冲中子、γ辐照SiGe HBT典型直流电参数和退火因子.在反应堆1×1013 cm2的脉冲中子注量和257 Gy(Si)γ总剂量辐照后,SiGe HBT静态共射极直流增益减小了20%.辐照后基极电流、结漏电流增大,集电极电流、击穿电压减小.初步分析了SiGe HBT瞬态中子、γ辐射损伤机理.     

塔里木盆地轮南一井磷灰石裂变径迹年龄及其热历史

通过轮南一井中的磷灰石裂变径迹分析表明,裂变径迹年龄随井深逐渐降低,到5500m时年龄降为零。生油窗为3100—6300m,成油期为40—180Ma。     

膜态沸腾条件下高温颗粒周围流体热动力特性的实验研究

利用已有的实验和理论基础 ,对高温球体与冷液在膜态沸腾条件下的多相混合结构进行详细的小规模实验研究 ,分析了单个高温颗粒在水中阻力受力的情况。发现高温小球在冷却剂中的速度比冷球的低 ,且随球温的升高而减小。目的是利用小规模实验研究单个高温颗粒的传热和阻力特性 ,可以分割各种在膜态高速沸腾条件下干扰换热与运动的影响因素 ,从而从本质上了解该结构条件下的热动力特性。     

Annihilation characteristics of positrons in free-standing thin metal and polymer films

Annihilation characteristics of positrons and positronium (Ps) in thin metal and polymer films were studied. Monoenergetic positrons were implanted into free-standing thin W and Au films and the annihilation γ-rays of positron-electron pairs were measured as a function of the incident energy of positrons. At the front-side surfaces of the films, an emission of Ps into vacuum and a resultant self-annihilation of ortho-Ps (o-Ps) were observed. At the backside surfaces, the Ps emission was found to be enhanced by an increase in the numbers of epithermal positrons and/or secondary electrons introduced by the impact of energetic positrons. For thin polymer films (polyester and polystyrene), the emission rate of o-Ps from the backside surfaces was higher than that from the metal films, which was attributed to the out-diffusion of o-Ps formed in the films. Those results suggested that the emission rate of Ps into vacuum was sensitive to the Ps formation process in the bulk and at the surface.     

Corrosion characteristics and oxide microstructures of Zircaloy-4 in aqueous alkali hydroxide solutions

The corrosion characteristics of Zircaloy-4 have been investigated in various aqueous solutions of LiOH, NaOH, KOH, RbOH and CsOH with equimolar M⁺ and OH⁻ at 350°C. The characterization of the oxides was performed using transmission electron microscope (TEM) and scanning electron microscope (SEM) on the samples which were prepared to have an equal oxide thickness in pre-transition and post-transition regimes. At a low concentration (4.3 mmol) of aqueous alkali hydroxide solutions, the corrosion rates decrease gradually as the ionic radius of cation increases. At a high concentration (32.5 mmol), the corrosion rate increases significantly in LiOH solution and slightly in NaOH solution, but in the other hydroxide solutions such as KOH, RbOH and CsOH, the corrosion rate is not accelerated. Even if the specimens have an equal oxide thickness in LiOH, NaOH and KOH solutions, the oxide microstructure formed in the LiOH solution is quite different from those formed in the NaOH or the KOH solutions. In the LiOH solution, the oxides grown in the pre-transition regime as well as in the post-transition regime have an equiaxed structure including many pores and open grain boundaries. The oxides grown in the NaOH solution have a protective columnar structure in the pre-transition regime but an equiaxed structure in the post-transition regime. On the other hand, in the KOH solution, the columnar structure is maintained from its pre-transition regime to the post-transition regime. On the basis of the above results, it can be suggested that the cation incorporation into zirconium oxide would control the oxide microstructure, the oxide growth mechanism at the metal–oxide interface and the corrosion rate in alkali hydroxide solutions.     

Modeling and analysis of thermal damping in heat exchanger tube bundles

Most structures and equipment used in nuclear power plant and process plant, such as reactor internals, fuel rods, steam generator tubes bundles, and process heat exchanger tube bundles, are subjected to flow-induced vibrations (FIV). Costly plant shutdowns have been the source of motivation for continuing studies on cross-flow-induced vibration in these structures. Damping has been the target of various research attempts related to FIV in tube bundles. A recent research attempt has shown the usefulness of a phenomenon termed as ‘thermal damping’. The current paper focuses on the modeling and analysis of thermal damping in tube bundles subjected to cross-flow. It is expected that the present attempt will help in establishing improved design guidelines with respect to damping in tube bundles.