质子辐照对Yb掺杂ZnO稀磁半导体薄膜缺陷与磁性的影响

采用电感耦合等离子体增强物理气相沉积法制备了Yb掺杂ZnO薄膜, 并采用不同剂量质子对薄膜进行了辐照实验, 重点采用X射线衍射、光电子能谱、正电子湮灭图谱和磁测量系统对Zn_0.985Yb_0.015O薄膜的缺陷和磁性能进行了研究。磁性测试结果表明: Zn_0.985Yb_0.015O薄膜经质子辐照后其饱和磁化强度随辐照剂量的增加逐渐增大, 当辐照剂量为6 × 10¹⁵ ions/cm²时, 其饱和磁化强度达到最大, 随着辐照剂量的进一步增加, 其饱和磁化强度反而变小。正电子湮灭图谱结果显示薄膜中主要存在锌空位相关的缺陷, 并且锌空位相关的缺陷随辐照剂量的变化与饱和磁化强度随辐照剂量的变化相一致。本研究从实验上揭示了在含有各种缺陷的Yb掺杂ZnO薄膜中, 锌空位缺陷是影响质子辐照Zn_0.985Yb_0.015O薄膜磁性的主要原因。     

Study of Nitrogen Implanted in Aluminum at Various Doses

Experimental and theoretical studies are carried out to understand transport of nitrogen in aluminum during implantation process. 60 keV and 120 keV N₂⁺ ion are implanted in pure Al substrates at doses ranging from l×l0¹⁷ to 9×l0¹⁷ N-atoms per cm². RBS and Glancing angle XRD studies are carried out. RBS studies show that the depth profiles are gaussian in nature at low doses and gradually become rectangular in shape as the dose increases. XRD analysis reveals that AlN is formed even at low doses. Theoretical simulations of depth profiles at low dose, include displacement mixing and radiation enhanced diffusion, which are modelled to be described by a diffusion like process. Effective diffusion coefficient in radiation environment is found to be equal to 8×l0^-16 cm².sec^-1. At high doses, when new N-atoms are added during implantation their transport gets linked with the already formed AlN. This leads to a rectangular shape of depth profiles observed at high doses.     

掺铈多组分硅酸盐玻璃电子辐照着色研究

采用吸收光谱、电子顺磁共振谱和光致发光谱对掺Ce多组分硅酸盐玻璃K509在10 MeV电子辐照下的色心动力学进行了研究。结果表明, 电子辐照引起K509玻璃可见光透过率降低的色心类型为非桥氧空穴色心HC1和HC2。在剂量率一定的情况下, 色心浓度随总剂量的增大呈指数函数增大; 在总剂量一定的情况下, 色心浓度随剂量率增大呈指数函数减小。Ce³⁺荧光强度的变化表明辐照过程中Ce³⁺浓度与辐照总剂量负相关, 与辐照剂量率正相关, 验证了掺Ce玻璃耐辐照机理: Ce³⁺吸收辐照产生的空穴从而抑制空穴色心HC1和HC2的形成, 且不引入额外的可见光波段吸收。通过对Ce³⁺宽带荧光峰进行高斯拟合, 得到了K509中Ce³⁺能级结构图。     

The effect of copper implantation on the mechanical, structural properties and residual stress of polycrystalline alumina

The effect of copper implantation on the mechanical properties, such as hardness, fracture toughness, and residual stress of alumina is addressed herein. The implantation conditions are conducted at room temperature on the polycrystalline alumina with doses ranged from 3 × 10¹⁶ to 10¹⁷ Cu cm⁻² (110 keV). The ion profile distribution was examined by Rutherford backscattering spectroscopy. Surface morphology was observed directly using scanning electron microscopy. Using the X-ray diffraction, we determined the crystallographic nature of the precipitates formed after heat treatment. The residual surface compressive stresses produced by these implantations, as determined by an indentation technique, ranged from 950 to 1720 MPa. Implantation caused a modification in the mechanical properties and an increase in the residual stress. The average residual compressive stress in the implanted region increases with fluence.     

Microstructural changes in oxygen-irradiated zirconium-based alloy characterised by X-ray diffraction techniques

We have carried out irradiation with 116 MeV O⁵⁺ ions on Zr–1Sn–1Nb–0.1Fe (ZIRLO) alloy at different doses and the microstructural parameters of the irradiated samples have been characterised by X-ray Diffraction Line Profile Analysis (XRDLPA). The average volume-weighted and surface-weighted domain size, microstrain and dislocation density have been estimated as a function of dose. There was a drastic decrease in domain size from unirradiated sample to the sample at a dose of 1 × 10¹⁷ O⁵⁺/m², but these values saturated with increasing dose of irradiation. The values of microstrain were found to increase with dose. The dislocation density increased almost by an order of magnitude for the samples irradiated with 1 × 10¹⁸ O⁵⁺/m² and 5 × 10¹⁸ O⁵⁺/m² as compared to the unirradiated samples.     

Implantation effect of diamond-like carbon films by 110 keV nitrogen ions

Diamond-like carbon films, grown on microscope slides by a dual-ion beam sputtering system, were implanted by 110 keV N⁺ under the doses of 1 × 10¹⁵, 1 × 10¹⁶ and 1 × 10¹⁷ions cm⁻² respectively. The implantation induced changes in electrical resistivity of the films and in infrared (IR) transmittance of the specimens were investigated as a function of implantation dose. The structural changes of the films were also studied using IR spectroscopy and Raman spectroscopy. It was observed that, with the increase of implantation dose, the diamond-like carbon films display two different stages in electrical and optical behaviours. The first is the increase of both the film resistivity and the IR transmittance of specimen at the dose of 1 × 10¹⁵ ions cm⁻² which, we consider, is attributed to the implantation-induced increase sp³ C---H bonds. However, when the doses are higher than 1 × 10¹⁵ ions cm⁻², the film resistivity and the IR transmittance of specimen decrea significantly and the decrease rates at dose range of 1×10¹⁶ to 1×10¹⁷ ions cm⁻² are smaller than those between 1×10¹⁵ and 1 × 10¹⁶ ions cm⁻². We conclude that the significant reductions of the two parameters at high doses are caused by the decreases of bond-angle disorder and of sp³ C---H bonds, the increases of sp² C---C bonds dominated the crystallite size and/or number and also the sp² C---H bonds. The smaller decrease rates at a dose range of 1 × 10¹⁶ to 1 × 10¹⁷ ions cm⁻² may be caused by further recombination of some retained hydrogen atoms to carbon atoms.     

单晶硅低能电子束辐照效应

利用Monter-Carlo方法,模拟低能一维平面电子束在本征、不同掺杂类型、掺杂浓度下的单晶Si中能量沉积分布情况。采用电子顺磁共振(EPR)技术测量了(111)晶向、两种掺杂类型下的掺杂浓度分别为1×1015cm-3、1×1017cm-3的单晶硅片在一定电子注量下辐照前后缺陷顺磁吸收谱,比较了样品辐照前后缺陷顺磁中心强度的变化,并用X光电子能谱(XPS)对Si-SiO2系统原子化学态的变化进行分析。结果表明,相比于P型Si,N型Si、特别是高掺杂的N型Si,在低能电子一定注量下,界面区内易引起辐射感生缺陷,主要来自于键合于磷的非桥联氧对空穴的诱捕作用,表现为POHC中心明显的变化,P2P芯能级谱突变。并根据理论和实验结果,对电子能量沉积、电离缺陷和辐照效应间的相互关系进行了分析。     

A study on the applicability of solid state, real-time dosimeters to the CMS experiment at the large hadron collider

MOSFET dosimeters have been exposed to a large range of radiation fields: 192 MeV positive pions, 500 MeV electrons, 23 GeV protons and a wide energy-spectrum of neutrons. This is the first time that pion dosimetry with MOSFETs is presented. The response curves of the devices are given, together with an evaluation of their dynamic range, showing that these dosimeters can be successfully used to monitor radiation fields up to very high doses and fluences. In the 500 MeV electron beam, an irradiation of p⁺/n/n⁺ diodes together with MOSFETs was also performed. The results of this irradiation show that both types of dosimeters can be used in CMS to monitor in real time the radiation environment.     

含钛氧化物弥散强化钢的微观组织和力学性能

采用粉末冶金工艺制备了含Ti氧化物弥散强化钢。使用电子背散射衍射方式研究了这种钢的晶粒形貌,使用透射电镜和高分辨率透射电镜表征了钢中析出相的形貌及种类,使用以同步辐射装置作为光源的小角度X射线散射技术和X射线吸收精细结构技术研究了钢中纳米尺寸析出相的分布特征和氧化物弥散强化钢中Y元素的存在形式,并测量了钢的力学性能。结果表明,含Ti氧化物弥散强化钢的晶粒多呈等轴状、平均晶粒尺寸为1.24 μm。钢中富Y、Ti、O纳米尺寸析出相的分布密度为1.39×10²⁴/m³,平均直径为2.23 nm。向材料中添加Ti元素改变了材料中Y原子的存在形式,生成了具有烧绿石结构的Y₂Ti₂O₇相和少量的富Cr、Mn相。这种钢的室温抗拉强度达到1324 MPa,随着测试温度的提高抗拉强度逐渐降低,延伸率逐渐提高。     

Underlying mechanisms for unique elastic properties of nanocrystalline Au

In order to get an insight into the grain boundaries (GBs) in nanocrystalline (n-) metal, we prepared the high-density n-Au with ρ/ρ₀>99% by the gas-deposition method and carried out the vibrating reed measurements, where ρ/ρ₀ is the relative density referring to the bulk density. The strain amplitude dependence (SAMD) of the resonant frequency (f) and the internal friction (Q⁻¹) was measured for the strain () amplitude between 10⁻⁶ and 2×10⁻³ and for temperature between 5 and 300 K. No plastic deformations are detected for the present strain range, where f decreases for up to 10⁻⁴ and then turns to increase, showing saturation for between 10⁻⁴ and 2×10⁻³. The low temperature irradiation by 2 MeV electrons or 20 MeV protons causes an increase in the Young’s modulus at 6 K, which is surmised to reflect a modification of the anelastic process in the GB regions. In contrast, the SAMD of f is hardly modified by irradiation, suggesting that it is indicative of a collective motion of atoms in n-Au.     

Radiation and cryogenic test results with a monolithic GaAs preamplifier in C-HFET technology

We report test results with a monolithic GaAs preamplifier fabricated in industrial C-HFET technology irradiated with a total dose of 10¹⁴ neutrons/cm² and 100 Mrad γ radiation and operated under cryogenic conditions. The measured gate current of the input transistor of a few nA increases by < 10% after irradiation. For a 330 μm input FET width, the equivalent noise charge (ENC) is typically 145 electrons per pF total input capacitance at a shaping time of 25 ns (bipolar) before irradiation and changes approximately by 10% after irradiation. Under cryogenic operation the corresponding input referred noise decreases by roughly a factor of two.     

γ辐照及热退火对光热折变玻璃光学性能的影响

对光热折变(Photo-thermal-refractive, PTR)玻璃在总剂量分别为0.35、1、10及100 kGy的γ射线下辐照, 并进行热退火处理, 采用吸收光谱、光致发光光谱及EPR电子顺磁共振谱研究了光热折变玻璃在γ射线辐照下的辐照机理。研究结果表明, γ辐照后的PTR玻璃在可见波段的吸收主要由银原子Ag⁰、银分子簇Ag₂、银分子簇Ag₃、银纳米颗粒Ag_m⁰及非桥氧空穴中心HC₁及HC₂引起; 在不同剂量γ射线辐照下, 玻璃基质中的变价离子(Ag⁺、Ce³⁺)价态先发生变化, 同时玻璃基质中的非桥氧键发生电离, 形成了非桥氧空穴型缺陷中心HC₁、HC₂。进一步增加辐照剂量, 产生了银的分子簇Ag₂和Ag₃; 同时玻璃基质中非桥氧空穴中心HC₂的浓度增大, 导致在639 nm附近的吸收增强。分别在不同温度下对辐照后的PTR玻璃进行相同时间的热处理及在低于T_g(玻璃转变温度)的温度下进行不同时间的热处理, 观察到250 ℃退火后PTR玻璃中HC₁及HC₂缺陷中心发生漂白; 并在430 ℃退火后出现了银纳米颗粒的吸收峰, 该吸收峰随退火时间的延长发生了红移及展宽。     

A TaSix barrier for low resistivity and high reliability of contacts to shallow diffusion regions in silicon

It is shown that a thin TaSi_x layer underneath the aluminium-based metallization considerably improves the contacts from the metallization to shallow diffusion regions in silicon. TaSi_x with x < 2 acts as a barrier against aluminium and silicon diffusion at the contacts and thus impedes aluminium spiking as well as silicon precipitates in the contacts. Furthermore the silicon erosion induced by high currents is reduced by one order of magnitude. The contact resistance to n⁺ -Si is decreased by a factor of 3–5. Finally the TaSi_x provides a low barrier Schottky diode on lightly doped n-Si and p-Si.     

硅藻土/g-C3N4复合材料的制备及其可见光增强活性

采用浸渍-焙烧法制备了具有可见光响应活性的硅藻土/g-C₃N₄复合光催化材料。利用TG、XRD、FE-SEM、HR-TEM、FT-IR、XPS、UV-Vis-DRS 和 PL谱等手段对其物相组成、形貌和光吸收特性进行表征。以RhB的光催化降解为探针反应评价催化剂的活性。光催化结果表明, 2.32wt%硅藻土/g-C₃N₄复合材料对RhB有较高的催化活性, 光催化降解的速率常数是纯g-C₃N₄的1.9倍。自由基捕获实验表明, ·O₂^-是RhB在硅藻土/g-C₃N₄复合材料上光催化降解的主要活性物种。光催化活性提高的主要原因在于硅藻土和g-C₃N₄之间静电作用有利于光生电子-空穴在g-C₃N₄表面的迁移, 进而提高g-C₃N₄的光催化活性。     

Phase stability under irradiation

Irradiation of metals and alloys with neutrons, electrons, heavy ions, or γ-rays may introduce up to 10⁸ J/mol of energy in the form of atomic displacements. This energy, which is in the form of vacancies, self-interstitials, and cores of displacement cascades is then available to produce a range of phase changes and microstructural alterations which are not observed under thermal conditions. There exist numerous mechanisms to convert part of this displacement energy into microstructural change, including irradiation-induced solute segregation, Frenkel pair recombination at the particle: matrix interface, irradiation disordering or amorphization, and recoil resolution of atoms from precipitates. In addition, the cores of displacement cascades may act as precipitate nucleation sites and Frenkel pair recombination may trigger spinodal-like instabilities.

The theory of these mechanisms is developed in some detail, and is followed by a systematic review of experimentals observations of irradiation-altered phase stability. The observations include enhanced nucleation on displacement cascades, precipitation induced by solute segregation to defect sinks, nucleation of wrong phases, disordering and amorphization, Frenkel pair recombination driven precipitate, and inverse Ostwald ripening.     

Investigation of Be diffusion in InGaAs using Kick-out mechanism

Be diffusion during post-growth annealing has been investigated in InGaAs epitaxial layers. Kick-out mechanisms considering species charges, build-in electric field and Fermi-level effect have been studied. Several forms of Kick-out mechanism have been implemented in our simulation programs. Experimental concentration profiles obtained by SIMS have been compared systematically with the results of simulations. We have deduced that the Kick-out mechanism Be_i⁰ Be⁻ + I_III⁺ is the dominating diffusion mechanism in InGaAs under our experimental conditions (C₀ = 3 × 10¹⁹ cm⁻³).     

High temperature oxidation of Ni–W coatings electroplated on steel

The high-temperature oxidation of Ni–16 at.% W coating electroplated on the steel substrate was studied at 700 and 800 °C in air. Before oxidation, the coating consisted of supersaturated, nanocrystalline Ni grains. During oxidation, oxygen diffused inward, Ni and the substrate elements such as Fe and Cr diffused outward. The outer NiO layer was not pure but had some dissolved ions of W⁶⁺ and Fe³⁺. Some Fe³⁺ ions were dissolved in the inner (NiO+NiWO₄) mixed layer, below which (W, Fe)-supersaturated, unoxidized Ni grains existed. Below these grains, tiny Ni–W–Fe precipitates, which were formed by the outward diffusion of Fe from the substrate, were surrounded by unoxidized (Fe-enriched, Cr-containing) Ni grains. Detailed oxidation mechanism of Ni–16 at.% W coating is proposed.     

High-Sensitivity Temperature Measurement With Miniaturized InSb Mid-IR Sensor

This paper reports the development and evaluation of an InSb photovoltaic infrared sensor (InSb PVS) operating at room temperature. The InSb PVS consists of 700 InSb p⁺ - p^- - n⁺ photodiodes connected in series, on a semi-insulating GaAs (100) substrate. An Al_0.17rIn_0.83Sb barrier layer between p⁺ and p^- layers was used to reduce diffusion of photo-excited electrons. Cutoff wavelength was 6.8 mum and output signal was almost linear with irradiance up to 0.6 mW/cm². Sensitivity of 67 muV/K and noise equivalent temperature difference of 2.2 mK/Hz^1/2 was obtained at room temperature, which shows the sensor to be a suitable for noncontact thermometry.     

加热和光照条件下Ru/TiO2催化二氧化碳甲烷化研究

本研究利用浸渍法制备了Ru/TiO₂催化剂, 并在光照和加热两种条件下考察了其催化二氧化碳与氢的反应, 发现催化剂在两种条件下均可引发显著的甲烷化反应(CO₂ + 4H₂ → CH₄ + 2H₂O)。结果显示, 在光照和加热(150~350℃)条件下, CH₄为唯一含C产物。而在更高温度的加热条件下(>400℃)除了生成CH₄外, 还产生少量CO副产物, 表明反应温度对产物选择性有显著影响。随着反应温度由150℃升高到550℃, 对于不同负载量的担载Ru催化剂, CO₂转化率均先增加后降低, 其中在Ru担载量为1.5wt%Ru/TiO₂催化剂上CO₂转化率在350℃时达到最高, 为77.58%。而在温度>400℃条件下, CO的选择性也随反应温度的升高而逐渐增加。综合反应结果和XRD、XPS和N₂吸附-脱附等表征结果, 发现二氧化碳与氢在光照和加热条件下(150~550℃)反应机制不同。在光照条件下, 光激发电子首先被金属Ru捕获, 进而将吸附在金属Ru上的二氧化碳还原, 活性物种经由RuC中间体形成CH₄。而加热条件下(150~550℃), H₂先被Ru活化成氢原子, 氢原子还原吸附在催化剂表面的CO₂形成RuC中间体, 最后RuC中间体进一步加氢生成CH₄。虽然在两种反应条件下经历相同的中间体, 但是中间体的形成路径不同, 即反应物CO₂被活化的方式不同, 因而产物选择性不同。     

N掺杂TiO2纳米纤维高可见光催化CO2合成甲醇

采用气相生长法在介孔SiO₂球的表面上制备了ϕ 8~10 nm的TiO₂纳米纤维, 采用相同的方法, 还成功地制备了氮掺杂的TiO₂(N-TiO₂) 纳米纤维, 它具有更高的可见光催化活性。采用X射线光电子能谱(XPS)、紫外光电子能谱(UPS)、X射线衍射(XRD)、扫描电镜(SEM)、透射电子显微镜(TEM)、紫外–可见分光光度计(UV-Vis)、荧光分光光度计(PL)等对样品进行了测试分析。TiO₂纳米纤维具有高结晶度的锐钛矿晶型, 掺氮后的TiO₂纳米纤维带隙变窄, 在可见光波段有明显的吸收, 同时, 光生电子还原能力更强, 大大提高了可见光下催化还原CO₂合成甲醇的产率。在300 W氙灯光照2 h后, 用纯TiO₂纤维催化CO₂合成甲醇, 产率为493.4 μmol•g^-1∙h^-1, 转换频率(TOF) 为0.089 h^-1; 以N-TiO₂为催化剂合成甲醇产率提高了40.1%, 达695.1 μmol∙g^-1∙h^-1, 转换频率(TOF) 提高了40.4%, 为0.125 h^-1。