B对Mo等元素在奥氏体钢/Cr2O3界面占位倾向影响的理论研究

超级奥氏体不锈钢中因含有更高铬、钼含量,具有极高的耐点蚀、晶间腐蚀性能,这与Mo等合金元素对钝化膜结构的影响密切相关,尤其含硼超奥钢钝化层表面Cr、Mo含量明显增加,但其原子层次的微观作用机制尚不清楚.本文采用第一性原理方法,研究了置换原子(Mo、Mn、Ni、Si),及间隙原子B在fcc-Fe/Cr₂O₃界面占位倾向,并分析了可稳定存在于界面B对这些元素偏析倾向的影响.结果表明:Mo、Mn、Ni、Si、B均可与fcc-Fe/Cr₂O₃界面结构体系形成稳定结构;Mo、Ni倾向分布于界面基体侧,Mo有向氧化层扩散的趋势,B处于fcc-Fe/Cr₂O₃界面基体侧更稳定,Mn、Si易分布于氧化层中;存在于界面B对四种元素在fcc-Fe/Cr₂O₃界面体系中的占位影响不同,有利于Mn、Mo偏析于界面基体侧,但抑制Mo向界面基体侧的偏析程度,使得Si、Ni更均匀的分布于基体. Mo等合金元素分布于界面时的态密度来看,界面处M...     

Ar的类氦和类锂离子与Mo表面相互作用过程中的x射线发射

在兰州重离子加速器国家实验室电子回旋共振离子源上用Si(Li)探测器观测到了不同动能的Ar¹⁵⁺和Ar¹⁶⁺离子与Mo表面相互作用过程产生的x射线.在不同动能 的Ar¹⁶⁺与Mo表面作用过程中不仅能观测到Ar的K层x射线而且能观测到Mo的L层x 射线.在不同动能的Ar¹⁵⁺入射下只能观测到Mo的L层x射线.实验结果表明，Ar的 K层x 射线的产额与入射离子的动能、作用过程中形成的空心原子携带的势能以及入射离子和靶原 子x射线的竞争等有关，Mo的L层x射线随入射离子动能的增加而增加. 关键词： x射线发射 高电荷态离子 Mo表面     

γ-Fe中氢扩散行为的第一性原理研究

不锈钢中氢脆问题一直是研究者们关注热点,然而至今为止,对于钢中合金元素及空位与H原子之间的作用机理依然不清晰.采用第一性原理方法研究了H原子在不同体系下γ-Fe(Fe₈H、Fe₇Cr/MoH、Fe₇H)的扩散激活能、扩散系数以及扩散过渡态,对比了H原子在不同体系γ-Fe中的扩散难易程度,并从电子结构层次解释其相互作用.研究结果表明,空位的存在会改变H原子在γ-Fe中的扩散路径.在含空位的晶胞中H原子稳定存在于空位附近的近四面体间隙中,并沿空位附近的四面体间隙或八面体到四面体间隙路径扩散. γ-Fe中空位对H原子的影响是局域性的,一方面是捕获H原子的陷阱;另一方面降低了H原子的扩散激活能,促进H原子的扩散.而Cr/Mo的掺杂会降低空位对H原子的束缚,也会抑制H原子的扩散.     

不同玻璃组分对β-NaYF4:Yb3+,Er3+/Tm3+粉体的侵蚀性研究及对发光性能的影响

选用硅酸盐、硼酸盐以及磷酸盐3种常用的玻璃体系,与β-NaYF₄:Yb³⁺,Er³⁺/Tm³⁺粉体均匀混合压片后在不同的温度(400～700 ℃)下进行热处理。采用X射线衍射技术和荧光光谱技术等测试手段研究不同玻璃形成体以及碱金属离子对β-NaYF₄:Yb³⁺,Er³⁺/Tm³⁺粉体的侵蚀情况以及对发光性能的影响。研究结果表明,在硼酸盐玻璃体系与β-NaYF₄:Yb³⁺,Er³⁺/Tm³⁺粉体复合热处理过程中,Li⁺和K⁺离子会取代β-NaYF₄晶体中Na原子的位置。 在相同热处理温度下,不同玻璃体系与β-NaYF₄晶体反应剧烈程度:磷酸盐>硼酸盐>硅酸盐。     

MoO_3/Si界面区钼掺杂非晶氧化硅层形成的第一性原理研究

采用基于密度泛函理论的第一性原理计算方法,通过模拟MoO_3/Si界面反应,研究了MoO_x薄膜沉积中原子、分子的吸附、扩散和成核过程,从原子尺度阐明了缓冲层钼掺杂非晶氧化硅(a-SiO_x(Mo))物质的形成和机理.结果表明,在1500 K温度下, MoO_3/Si界面区由Mo, O, Si三种原子混合,可形成新的稳定的物相.热蒸发沉积初始时, MoO_3中的两个O原子和Si成键更加稳定,同时伴随着电子从Si到O的转移,钝化了硅表面的悬挂键. MoO_3中氧空位的形成能小于SiO_2中氧空位的形成能,使得O原子容易从MoO_3中迁移至Si衬底一侧,从而形成氧化硅层;替位缺陷中, Si替位MoO_3中的Mo的形成能远远大于Mo替位SiO_2中的Si的形成能,使得Mo容易掺杂进入氧化硅中.因此,在晶硅(100)面上沉积MoO_3薄膜时, MoO_3中的O原子先与Si成键,形成氧化硅层,随后部分Mo原子替位氧化硅中的Si原子,最终形成含有钼掺杂的非晶氧化硅层.     

Cu/CeO2(110)界面特性的第一性原理研究

Cu-CeO₂体系因其特殊的催化能力而在固体氧化物燃料电池和水煤气转化反应等多个催化领域有重要应用. 采用基于密度泛函理论的第一性原理方法, 在原子和电子层面上系统地研究了单个Cu原子及Cu小团簇在CeO₂(110)面上的吸附构型, 价键特性和电子结构, 结果表明: 1) 单个Cu原子的最稳定吸附位是两个表面O的桥位; 2) Cu团簇的稳定吸附构型为扭曲的四面体结构; 3) Cu原子及Cu团簇的吸附在CeO₂(110)面的gap区域引入了间隙态, 这些间隙态主要来自于Cu及其近邻的O和表层还原形成的Ce³⁺, 间隙态的出现表明Cu的吸附增强了CeO₂(110)表面的活性; 4) 吸附的单个Cu原子及Cu团簇分别被CeO₂(110)面表层的Ce⁴⁺离子氧化形成了Cu^δ+和Cu₄^δ+, 并伴随着Ce³⁺离子的形成, 这个反应可归结为Cu_x/Ce⁴⁺→Cu_x^δ+/Ce³⁺; 5) Cu团簇的吸附比Cu单原子的吸附引入了更多的Ce³⁺离子, 进而形成了更多的Cu^δ+-Ce³⁺催化活性中心. 结合已报道的Cu/CeO₂(111)界面特性, 更加全面地探明了Cu与CeO₂(111)和(110)两个较稳定低指数表面的协同作用特性, 较为系统地揭示了Cu增强CeO₂催化特性的原因及Cu与CeO₂协同作用的内在机理. 关键词： 2')" href="#">Cu/CeO₂ U')" href="#">DFT+U 吸附 电子结构     

吸附Al,Sn后Si(111)面的电子结构及其比较

通过对吸附原子和衬底Si原子由于相互作用而产生的轨道交叠占有几率(OOP)和集团态密度的分析发现吸附Al和吸附Sn的Si(111)面能带中电子的占据状态很不一样,Si(111)3^1/2×3^1/2-Sn中有一个半充满的表面带,从而使体系具有表面金属性。而Si(111)3^1/2×3^1/2-Al中电子填满吸附原子和表面Si原子成键的表面态,反键的表面态全空,因此吸Al后的Si(111)面可能出现半导体特性。计算结果与实验结果 关键词：     

高剂量离子注入形成的非晶层重新结晶过程中杂质外扩散的物理模型

本文提出了一个杂质沉淀引起位错生成、位错-杂质相互作用、杂质原子沿晶粒间界快速扩散的模型,用以解释高剂量离子注入形成的非晶层在重新结晶的退火过程中杂质外扩散和缺陷运动现象。给出了在位错的合应力场的影响下杂质的扩散方程。以能量为80keV,剂量为10¹⁶cm^-2的Pb⁺注入Si(111)面为例,对扩散方程进行了数学物理处理,从而给出了根据实验测量推演表观扩散系数随时间变化及位错的合应力场对杂质的作用力的纵向分布的方法。实验测得的位错合应力场对杂质的作用系数α≈8.4×10^-28dyn·cm³,退火时间在5×10³sec至8.25×10³sec内,表观扩散系数D随时间的变化为一指数关系。 关键词：     

BF2+注入多晶硅栅常规热退火氟迁移特性的二次离子质谱分析

借助二次离子质谱（SIMS）技术，深入地、系统地分析了80keV，2×10¹⁵ cm^-2BF₂⁺注入多晶硅栅在常规热退火条件下，F在多晶硅栅中的分布及迁移特性．F在多晶硅栅中的迁移，不但存在着扩散机制，而且还存在着发射和吸收机制，据此成功地解释了实验结果 关键词：     

CrHn(n=0,+1,+2)分子及离子的势能函数

用原子分子反应静力学原理推导出CrHⁿ(n=0，+1，+2)的电子状态及其离解极限. 对H原子采用6-311++G^**基组，对Cr原子采用SVP(split valence polarization)全电子基组，用B3PW91方法计算了它们的平衡几何、电子状态，在此基础上分别计算CrH，CrH⁺的Murrell-Sorbie解析势能函数和CrH²⁺的解析势能函数及其对应的力常数、光谱参数，理论计算值与实验值和文献计算值符合较好. 从离解极限和通道解释了不同的势能函数形状. 计算表明：CrH⁺的势能曲线均具有对应于稳定平衡结构的极小点，说明CrH⁺可稳定存在. 而CrH²⁺离子的势能曲线对应于不稳定的排斥态，说明CrH²⁺是不稳定的. 关键词： n(n=0')" href="#">CrHⁿ(n=0 +2) 势能函数 光谱参数 稳定性     

Mechanism of ion-induced mixing phenomena in Gold–Nickel bilayer on Si substrate

Gold/Nickel bilayer thin films deposited on Si(100) substrates are bombarded by 100 keV ⁴⁰Ar⁺, 260 and 300 keV ⁸⁴Kr²⁺ and 400 keV ¹³²Xe³⁺ ions which deposit maximum energy across the Gold/Nickel interface and hence produce maximum atomic transport within two sides of the interface. However, due to the energy of the projectile ions some Si atoms have also gained energy, which, in turn, displaces the atoms. The atomic displacements caused by the projectile in the system has been analyzed using RBS, XRD, SEM/EDS and AFM/MFM techniques. The relative change in the variance of the intermixed region across the Au–Ni–Si interfaces excluding the irradiation-induced surface roughness has been calculated and it was observed that it increases linearly with ion fluence. The measured athermal mixing rates which vary between 3.7 and 6.9 nm⁴, have been explained by various existing phenomenological models. It shows that local or global thermal spike models are most suitable for explaining the ion beam-induced mixing of systems with strong thermochemical properties of the constituents. The mixing efficiency of this system has been calculated and found to be 1.2 nm⁵/keV.     

Synthesis of molybdenum silicide by both ion implantation and ion beam assisted deposition

Two groups of Mo/Si films were deposited on surface of Si(1 0 0) crystal. The first group of the samples was prepared by both ion beam assisted deposition (IBAD) and metal vapor vacuum arc (MEVVA) ion implantation technologies under temperatures from 200 to 400 °C. The deposited species of IBAD were Mo and Si, and different sputtering Ar ion densities were selected. The mixed Mo/Si films were implanted by Mo ion with energy of 94 keV, and fluence of Mo ion was 5 × 10¹⁶ ions/cm². The second group of the samples was prepared only by IBAD under the same test temperature range. The Mo/Si samples were analyzed by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), sheet resistance, nanohardness, and modulus of the Mo/Si films were also measured. For the Mo/Si films implanted with Mo ion, XRD results indicate that phase of the Mo/Si films prepared at 400 and 300 °C was pure MoSi₂. Sheet resistance of the Mo/Si films implanted with Mo ion was less than that of the Mo/Si films prepared without ion implantation. Nanohardness and modulus of the Mo/Si films were obviously affected by test parameters.     

AES analysis of nitridation of Si(100) by 2–10 keV N+2 ion beams

Ion beam nitridation of Si(100) as a function of N⁺₂ ion energy in the range of 2–10 keV has been investigated by in-situ Auger electron spectroscopy (AES) analysis and Ar⁺ depth profiling. The AES measurements show that the nitride films formed by 4–10 keV N⁺₂ ion bombardment are relatively uniform and have a composition of near stoichiometric silicon nitride (Si₃N₄), but that formed by 2 keV N⁺₂ ion bombardment is N-rich on the film surface. Formation of the surface N-rich film by 2 keV N⁺₂ ion bombardment can be attributed to radiation-enhanced diffusion of interstitial N atoms and a lower self-sputtering yield. AES depth profile measurements indicate that the thicknesses of nitride films appear to increase with ion energy in the range from 2 to 10 keV and the rate of increase of film thickness is most rapid in the 4–10 keV range. The nitridation reaction process which differs from that of low-energy (< 1 keV) N⁺₂ ion bombardment is explained in terms of ion implantation, physical sputtering, chemical reaction and radiation-enhanced diffusion of interstitial N atoms.     

Mixing of Au in Si induced by secondary and high-order recoil implantation

The mixing of Au in Si induced by secondary and high-order recoil implantation was investigated using 350 keV Ar⁺ and 350 keV Kr⁺ ions to fluences from 1?×?10¹⁶ to 3?×?10¹⁶ ions/cm² at room temperature. The thickness of the Au layer evaporated on Si substrate was ～2400 Å.The ranges of the Ar and Kr ions were chosen to be lower than the thickness of the Au layer in order to avoid the ballistic mixing produced by the primary knock-on atoms. Rutherford backscattering spectrometry (RBS) experiments were carried out to study the effects induced by Ar and Kr irradiation at the interface of Au–Si system. We observed that in the case of the irradiation with Ar⁺ ions, a broadening of the Au–Si interface occurred only at the fluence of 3?×?10¹⁶ Ar⁺/cm² and it is attributed to the surface roughening induced by ion bombardment. In contrast, the RBS analysis of a sample irradiated with 2?×?10¹⁶ Kr⁺/cm² clearly showed, in addition to the broadening effect, the formation of a mixed zone of Au and Si atoms at the interface. The mixing of Au in Si atoms can be explained by the secondary and high-order recoil implantation followed by subsequent collision cascades.     

Ion beam mixing of Al/Fe binary systems

Ion beam mixing of Al layers on Fe and Fe layers on Al are studied by irradiation with 200 keV Xe⁺-ions at room temperature as a function of the thickness of the top layer and of the ion fluence from 5×10¹⁵ to 7.5×10¹⁶ions/cm². Deconvolution procedures are needed to separate the influence of the ion sputter profiling by AES from the ion beam induced mixing effects. Auger electron spectroscopy data reveal that the mixing induced diffusivity ought to be considered as a function of concentration. The diffusion coefficients are evaluated by the Boltzmann-Matano method. A strong dependence of the diffusion coefficients and also the mixing efficiencies from the ion dose, the depth of the interface and the nuclear energy deposition were observed. Results are discussed in terms of the diffusional and collisional mixing as well as chemical affinity of both Fe and Al.     

Processing for optically active erbium in silicon by film co-deposition and ion-beam mixing

Techniques of film deposition by co-evaporation, ion-beam assisted mixing, oxygen ion implantation, and thermal annealing were been combined in a novel way to study processing of erbium-in-silicon thin-film materials for optoelectronics applications. Structures with erbium concentrations above atomic solubility in silicon and below that of silicide compounds were prepared by vacuum co-evaporation from two elemental sources to deposit 200-270 nm films on crystalline silicon substrates. Ar⁺ ions were implanted at 300 keV. Oxygen was incorporated by O⁺-ion implantation at 130 keV. Samples were annealed at 600 °C in vacuum. Concentration profiles of the constituent elements were obtained by Rutherford backscattering spectrometry. Results show that diffusion induced by ion-beam mixing and activated by thermal annealing depends on the deposited Si-Er profile and reaction with implanted oxygen. Room temperature photoluminescence spectra show Er³⁺ transitions in a 1480-1550 nm band and integrated intensities that increase with the oxygen-to-erbium ratio.     

Phase transition and pitting corrosion behaviour for Mo—implanted aluminium

Molybdenum ions are implanted into aluminium with high ion flux and high dose at elevated temperatures of 200℃, 400℃ and 500℃. Due to the high temperature and high flux of vacancies and interstitial atoms, the atom diffusion and chemical effects are enhanced during the ion implantation. The effects increase with increasing ion flux and dose, so that new phase formation and phase transition emerge noticeably. X-ray diffraction analysis shows that when the aluminium is implanted with Mo ions at a low ion flux (25μA/cm²), the Al₅Mo alloy is formed. The atomic ratio of Mo/Al of the Al₅Mo phase is close to 20%. When the aluminium is implanted with Mo ions at a high ion flux (50μA/cm²), the phase transition from Al₅Mo to Al₁₂Mo appears, and the latter is dominant, which is determined to be the final phase. The ratio of Mo/Al in Al₁₂Mo is 7.7%. Rutherford backscattering spectroscopy indicates also that the Mo/Al atom ratio is ～7% to ～8% in Mo-implanted aluminium. The atomic ratios of the constituents in Al₅Mo and Al₁₂Mo are of stoichiometric composition for these alloys. The thicknesses of the Al₁₂Mo alloy layers for Mo-implanted Al with ion doses of 3×10¹⁷/cm² and 1×10¹⁸/cm² are 550nm and 2000nm, respectively. The pitting corrosion potential V_p increases obviously. It is clear that due to the formation of Al₁₂Mo alloy layer, the pitting corrosion resistance is enhanced.     

Atomic mixing of Ni2O3/SiO2, NiO/SiO2, and Ni/SiO2 interfaces induced by swift heavy ion irradiation

We have investigated the interface mixing of Ni₂O₃/SiO₂, NiO/SiO₂, and Ni/SiO₂ induced by the irradiation with Ar, Kr and Xe ions of energies ranging from 90 MeV to 260 MeV. Since these energies are in the electronic stopping regime, atomic transport processes will not be directly initiated by elastic ion–target collisions, but need to be excited by secondary processes like electron–phonon coupling or Coulomb explosion. Nevertheless, we have observed a strong mixing effect in the ceramic systems if the electronic energy loss exceeds a certain threshold value. Estimation of an effective diffusion constant indicates that diffusion takes place in the molten ion track. In contrast to the ceramics, the metallic Ni layer is still insensitive even for the highest electronic stopping power used (S_e=28 keV/nm) and does not exhibit mixing with its SiO₂ substrate. In addition, NiO/SiO₂ and Ni/SiO₂ were irradiated in the nuclear stopping regime with 600 keV Kr and 900 keV Xe–ions. Here the intermixing effect is in good agreement with the assumption of ballistic atomic transport. Received: 5 February 2002 / Accepted: 11 February 2002 / Published online: 3 May 2002 RID="*" ID="*"Corresponding author. Fax: +49-711/685-3866, E-mail: bolse@ifs.physik.uni-stuttgart.de     

Interface growth mechanism in ion beam sputtering-deposited Mo/Si multilayers

Despite the technological importance of metal/Si multilayer structures in microelectronics, the interface reactions occurring during their preparation are not yet fully understood. In this work, the interface intermixing in Mo/Si multilayer coatings has been studied with respect to their preparation conditions. Various samples, prepared at room temperature with different Mo deposition rates (0.06–0.43?Å?s^?1) and a constant Si rate, have been investigated by detailed TEM observations. Contrary to the Si-on-Mo interface where no evidence of chemical intermixing could be found, the Mo-on-Si interface presents a noticeable interface zone whose thickness was found to noticeably decrease (from 4.1 to 3.2?nm) when increasing the Mo deposition rate. Such intermixing phenomena correspond to diffusion mechanisms having coefficients ranging from 0.25?×?10^?15 to 1.2?×?10^?15?cm²?s^?1 at room temperature. By assuming a diffusion mechanism mainly driven by Mo–Si atomic exchanges to minimize the surface energy, the diffusion dependence with Mo deposition rate has been successfully simulated using a cellular automaton. A refined simulation including Mo cluster formation is also proposed to explain the scenario leading to the full crystallization of Mo layers.     

Swift heavy ion beam mixing at V/Si interface

Vanadium silicides are of increasing interest because of applications in high temperature superconductivity and in microelectronics as contact materials due to their good electrical conductivity. In the present work ion beam induced mixing at Si/V/Si interface has been investigated using 120 MeV Au ions at 1 × 10¹³ to 1 × 10¹⁴ ions/cm² fluence at room temperature. V/Si interface was characterized by Grazing Incidence X-Ray Diffraction (GIXRD), Atomic Force Microscopy (AFM), Rutherford Backscattering Spectrometry (RBS) and Cross-sectional Transmission Electron Microscopy (XTEM) techniques before and after irradiation. It was found that the atomic mixing width increases with ion fluence. GIXRD and RBS investigations confirm the formation of V₆Si₅ silicide phase at the interface at the highest ion irradiation dose.