Substrate effect on electronic sputtering yield in polycrystalline fluoride (LiF, CaF2 and BaF2) thin films

Influence of substrate on electronic sputtering of fluoride (LiF, CaF₂ and BaF₂) thin films, 10 and 100 nm thin, under dense electronic excitation of 120 MeV Ag²⁵⁺ ions irradiation is investigated. The sputtering yield of the films deposited on insulating (glass) and semiconducting (Si) substrates are determined by elastic recoil detection analysis technique. Results revealed that sputtering yield is higher, up to 7.4 × 10⁶ atoms/ion for LiF film on glass substrate, than that is reported for bulk materials/crystals (∼10⁴ atoms/ion), while a lower value of the yield (2.3 × 10⁶ atoms/ion) is observed for film deposited on Si substrate. The increase in the yield for thin films as compared to bulk material is a combined effect of the insulator substrate used for deposition and reduced film dimension. The results are explained in the framework of thermal spike model along with substrate and size effects in thin films. It is also observed that the material with higher band gap showed higher sputtering yield.     

Photoluminescence properties of SHI induced F2 and F3 color centers in nano-granular LiF thin films

Photoluminescence (PL) properties of swift heavy ions-induced F₂ and F₃⁺ color centers in nano-granular lithium fluoride (LiF) thin film were studied. LiF films were deposited on glass and silica substrates and irradiated with various ion species (Ag, Ni and Au) at different irradiation temperatures. The role of ion species, their fluence and the irradiation temperature on the PL intensity of color centers induced in LiF thin films is discussed.     

Proton-induced F-centers in LiF and MgF2

The growth of F-centers in LiF irradiated at room temperature with 40- and 85-MeV protons and with ⁹⁰Sr electrons was found to be proportional to the square root of the absorbed energy over the range 0.5 to 2.3 Mrad which corresponds to an F-center density range of 1 × 10¹⁶ to 1.5 × 10¹⁷ per cm³. The production efficiency was 5 × 10³eV per F-center at an absorbed energy of 2.3 Mrad. The density of F-centers produced in MgF₂ by 40- and 85-MeV protons was measured over an absorbed energy range of 0.2 to 29 Mrad which corresponds to a maximum F-center density of 2 × 10¹⁶ per cm³. The production efficiency for MgF₂ was 4 × 10⁵eV per F-center at an absorbed energy of 16 Mrad.     

MgF2作为镁离子内扩散LiNbO3单晶扩散源的研究

利用ＭｇＦ₂作为扩散源进行镁离子内扩散ＬｉＮＯ₃单晶基片的研究．经电子探针显微镜分析表明，镁的扩散层镁离子浓度分布具有近似半抛物形和阶跃形分布，并得到镁的激活能为１０４ＫＪ／mol.X射线衍射分析发现，当镁离子内扩散超过一定程度时，在镁的扩散层出现具有ＬｉＮｂ₃Ｏ₈的物相结构，并发现该物相结构的出现与ＬｉＮＯ₃体内锂离子的外扩散和扩散表面氟离子的存在有关．由扫描电子显微镜观察到氟离子以ＬｉＦ的形式出现，并随着扩散程度的增大，挥发和脱离开扩散层表面． 关键词：     

Effect of deposition method on the optical and microstructural properties of vacuum-deposited MgF2 thin films

The optical and structural properties of magnesium fluoride films deposited by conventional e-beam evaporation and sputtering have been investigated herein. Deposition processes were carried out on the glass substrates in the absence of any reactive gases. The results show that the deposition method has a considerable effect on the optical and microstructural properties MgF₂ film. Also, the results show that the deposition parameters of the sputtered MgF₂ films can be easily controlled to yield the desired layer. The optical, chemical, and structural properties of the deposited MgF₂ films were characterized by using spectrophotometer, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, and atomic force microscopy.     

Absolute quantum yields of Cr3+2E → 4A2 emission in solids

The absolute quantum yields of powders have been obtained. The correction factors involved in using this method are described. The room temperature yield of ruby, 0.63 (⁴T₂←⁴A₂ excitation), is in good agreement with the previously reported single crystal results. No change in ruby quantum yield accompanies temperature reduction to 80°K. The absolute quantum yields of dilute (1–2%) Cr³⁺ in NaMgAl (C₂O₄)₃?9H₂O powders are 0.27 at 80°K. A small but measurable concentration dependence is observed with this system. Evidence to support an intramolecular intersystem crossing efficiency of unity is presented.     

Sputtering yields of PMMA films bombarded by keV C60 ions

A quartz crystal microbalance (QCM) has been used to determine total-mass sputtering yields of PMMA films by 1-16 keV C₆₀^+,2+ ion beams. Quantitative sputtering yields for PMMA are presented as mass loss per incident ion Y_m. Mass-lost rate QCM data show that a 13 keV C₆₀ cluster leads to emission equivalent to 800 PMMA molecules per ion. The power law obtained for the increase in sputtering yield with primary ion energy is in good agreement those predicted by “thermal spike” regime and MD models, when crater sizes are used to estimate sputtering.     

超新星爆发环境核素56,57,59,60Co的电子俘获

基于壳模型与Random Phase Approximation理论, 利用Shell-Model Monte Carlo方法, 研究了超新星爆发环境核素^56,57,59,60Co的电子俘获与电子丰度变化率. 我们的结果与利用Aufderheide方法计算的结果进行了误差对比. 结果表明: 电子俘获率受温度和密度的影响大大增加, 甚至增加达6个数量级以上(如在ρ₇=0.43, Y_e=0.48核素^57,59,60Co). 另一方面, 随着温度和密度的增大, 电子丰度变化率大大降低, 甚至减小达5个数量级以上(如在ρ₇=5.86, Y_e=0.47核素⁵⁹Co). 通过对误差因子的分析表明, 在低温低密度环境二种结果误差较大; 而在高温高密度环境, 二种结果误差相对较小. 关键词： 电子俘获 超新星     

35MeV/u40Ar+197Au中的熵产生

根据量子统计模型(QSM)的计算分析,找到了一个提取核反应过程中熵产生的新的可观测量.核反应过程中约化d的产额d/(d+t+³He+⁴He)和熵有单调的函数关系,并且和体系的碎裂密度(ρ/ρ₀)及体系的N/Z都无关,可以作为提取核反应过程中熵产生的一个观测量.和目前已经有的其他方法相比,约化d产额这一提取熵方法可以用于较低能量的重离子核反应中,并且数据处理分析简单.对于35MeV/u⁴⁰Ar+¹⁹⁷Au的核反应过程所提取的熵和利用约化带电粒子多重性提取的熵结果一致.结合后角类靶热核发射体系实验提取的同位素核温度为4.7±1.2MeV及S/A=2.5±0.5,根据熵和核温度的关联关系,可以确定其Break up密度接近但小于0.1(ρ/ρ₀) 关键词： 熵 约化d产额 核温度 统计发射     

129Xeq+轰击N型和P型Si表面时的电子发射产额研究

在兰州重离子加速器国家实验室测量了1.8 MeV Xeq+离子分别轰击N型和P型Si两种靶材表面时的电子发射产额。实验中,通过改变入射离子的电荷态,研究了入射离子势能沉积对两种靶材表面电子发射产额的贡献。结果发现同一离子入射时,N型Si表面的电子发射产额高出P型Si表面的电子发射产额约12.5%;对于具有相同入射动能的Xeq+离子,两种靶材表面的电子发射产额均随着入射离子势能的增加而线性增加。此外,还测量了3.4 MeV Xeq+离子分别轰击以上两种靶材时的电子发射产额,得到了类似的结果。本文利用功函数分别从动能电子发射和势能电子发射两个角度对实验结果进行了分析讨论。The electron emissions from N-type Si and P-type Si induced by 1.8 MeV 129Xeq+are measured in the National Laboratory of Heavy Ion Research Facility in Lanzhou,The contribution to electron emission yield from potential energy of incident ions is studied through changing the charge state of incident ions.The results show that for the same incident ion,electron emission yield of N type Si surface is higher than that of P-type Si surface about 12.5%.For incident ions with the same kinetic energy,both electron emission yields of two targets increase linearly with incident ion energy.In addition,the electron emissions induced by 3.4 MeV 129Xeq+from N-type Si and P-type Si mentioned above are measured,which give similar results.The experimental results are analyzed and discussed using work function from two angles of the kinetic electron emission and the potential energy electron emission.     

The temperature dependence of penning ionization electron energy spectra: He(23S)—ar,N2, NO,O2, N2O,CO2

Using two intense thermal energy He(2³S) sources of different temperatures (≈400 and ≈ 1000 K, resp.) and a transmission-calibrated electron energy analyzer with about 30meV resolution, the dependence of He(2³S) Penning ionization electron spectra on collision energy for the target species Ar, N₂, NO, O₂, N₂O and CO₂ have been studied. The energy shifts of the Penning electron energy distributions and the branching ratios for the population of different electronic states in the molecular ions are determined quantitatively and compared for the two different collision temperatures. These results and the shapes of the observed Penning electron energy distributions are discussed in the light of current models for the Penning procen; the observed temperature dependences are correlated with the nature of the ionized orbitals in cases of only one entrance channel (closed shell targets) and, in addition, to the existence of qualitatively different entrance channels (open shell targets).     

MeV氢微团簇离子与固体介质的电荷交换

利用静电加速器提供的0.6—1.8MeV的H⁺，H⁺₂，H⁺₃离子，轰击不同厚度的碳膜，分别测量这些离子通过碳膜后各种产物的产额. 得到了不同能量的H⁺通过碳膜后中性原子H和负离子H^-的产额随入射质子速度的变化关系；分别得到能量为1.2MeV,1.8MeV的H⁺₂，H⁺₃团簇离子通过不同厚度碳膜的透射产额及其与团簇离子在碳膜中驻留时间的关系；对结果进行了理论分析与讨论. 关键词： 团簇离子 电荷交换     

射频反应性溅射沉积的Cd2SnO4薄膜物理性质与缺陷特性研究

在Ar+O₂混合气氛中射频反应性溅射Cd-Sn合金靶制备了透明导电Cd₂SnO₄(简称CTO)薄膜。用X射线衍射测量了CTO膜的结构。实验结果表明,这种薄膜的电学和光学性质依赖于混合气体中的氧浓度、衬底温度以及沉积后的热处理。获得的CTO膜最低电阻率为1.74×10^-6Ω·cm,可见光光谱区最高透射率为95％。对于氧浓度为6％、衬底温度为400℃时沉积的CTO膜,经热处理后,其光隙能由热处理前的2.37eV增大为2.6 关键词：     

立方体AgCl微晶中［Fe(CN)6］4-引入的浅电子陷阱阱深与俘获截面的动力学模拟

为了描述在晶体生长阶段掺入［Fe(CN)₆］^4-的立方体AgCl微晶中 光电子的产生与 衰减过程，建立了一种由三个固有中心和一个浅电子陷阱(SETs)组成的动力学模型，并引出一组微分方程.通过求解微分方程得到与实验结果相符合的光电子衰减曲线及其寿命.调整相 关模拟参数，于常温下得到由［Fe(CN)₆］^4-引入的SETs阱深为0.1 15eV，电子俘获截面为2.136×10^-17cm². 关键词： 光电子 浅电子陷阱 俘获截面 AgCl微晶     

The (d, 6Li) reaction on 12C, 16O, 24Mg, 40Ca and 58Ni at 54.25 MeV

The (d, ⁶Li) reaction was studied at E_d = 54.25 MeV on the target nuclei ¹²C, ¹⁶O, ²⁴Mg, ⁴⁰Ca and ⁵⁸Ni. The data were analyzed with finite-range DWBA calculations. The absolute values of the α-cluster spectroscopic factors and the target mass dependence of the relative S_α were in agreement with those in the (p, pα) reaction at E_p = 100 and 157 MeV. The theoretical calculations of the relative S_α were in better agreement with the experimental data at higher energy than at the lower energies.     

On the fusion cross section for 16O + 12C

The total fusion cross section σ_f for ¹⁶O + ¹²c.m. has been measured in 250 keV steps between 17 and 28 MeV c.m. energy via γ-ray techniques. Individual yields for 10 nuclides in the evaporation chain were determined. The oscillations in σ_f, which agree in gross structure but not in detail with previous work, appear to be most closely associated with reactions leading to ²⁰Ne. It is observed that the reaction yield is >80% dominated by nuclides having at least one α particle in the evaporation chain.     

Ho3+掺杂对ZnO薄膜的微观结构和磁性的影响

研究Ho³⁺掺杂对氧化锌半导体材料的微结构和磁学性质影响. 利用热蒸发技术制备了一系列沉积在Si(100)衬底的Zn_1-xHo_xO(x=0.0、0.04、0.05）薄膜. X射线光谱、表面形貌以及磁性的实验结果表明,Ho³⁺掺杂对ZnO薄膜材料的性能影响很大. X射线衍射图显示峰位出现高角度转变并且趋向于(101)取向,在ZnO晶格显示Ho³⁺置换. 扫描电子显微镜和能谱仪对薄膜的表面形貌以及化学     

电子与类铍N3+和O4+离子碰撞激发截面的相对论扭曲波计算

采用全相对论扭曲波方法,系统地计算了类铍N³⁺和 O⁴⁺离子从基态到2s2p和2p² 的各激发态以及从亚稳态到2p²各激发态的电子碰撞激发截面,详细地讨论了靶态的关联效应对激发截面的影响.结果表明：对于2s-2p的单电子激发,在低能碰撞时,靶态的电子关联效应起非常重要的作用,且使得激发截面降低;而高能碰撞时,靶态波函数的描述对连续态波函数的影响比较小,对激发截面影响也比较小.对于2s²-2p²的双电子激发,其中基态2s²¹S₀到J=0的2p²³P₀,¹S₀的激发截面较大,其主要原因是末离子态波函数与基组态波函数的混合,但是其他几个激发的激发截面较小. 关键词： 全相对论扭曲波方法 电子碰撞激发 电子关联效应     

Ion-induced secondary electron emission from ZnS thin films deposited by closed-spaced sublimation

ZnS thin films were deposited on soda lime glass and aluminum substrates by close-spaced sublimation technique. The change in composition, structural and optical properties of the films was investigated as a function of the substrate temperature. The deposited films were stoichiometric and crystalline in nature having cubic structure oriented only along (1 1 1) plane. The energy band gap of the films deposited at the substrate temperature of 150, 250 and 350 °C was 3.52, 3.58 and 3.63 eV respectively. These films were then bombarded with 2-10 keV energy pulsed Ar⁺ beam and their electron yield was determined from impinging ion and emitted electron currents. The electron yield of ZnS films was much high as compared to the metals. The electron yield of ZnS films increased with energy of the incident ion and got saturated at about 8 keV. The most important result of this study was that the electron yield of ZnS films having same composition was different. Monte Carlo simulations performed to interpret these experimental findings showed that the dissimilar electron yields of ZnS films is due to the combined effect of energy band gap, surface barrier potential and density of the films.     

Superlong pulses of laser oscillation on the 6 1P1-5 1D2 transition of the barium atom

A possibility of CW laser oscillation on atomic transitions between a resonance energy level and a metastable one under conditions when lower laser states are deactivated by electron impacts has been theoretically shown. We determined the plasma parameters so that CW laser action on such transitions of Cu, Au, Ca and Ba atoms may be possible. Superlong laser pulses of 6 μs duration were obtained on the 6 ¹P₁-5 ¹D₂ transition of the barium atom.