Interaction of hydrogen and deuterium with intrinsic atomic defects in high-purity electron-irradiated nickel

Abstract

High-purity nickel was irradiated with 2 MeV electrons at temperatures below 80 K to a dose of 1 × 10²³ e^?/m² in the as-prepared state and after charging with H or D. By means of magnetic after-effect measurements relaxations of anisotropic radiation-induced defects and of defect-hydrogen complexes were investigated in the temperature range between 4.2 and 500 K. The isochronal annealing behaviour of these relaxations and the isochronal recovery of the residual resistivity was measured simultaneously on the same specimens. At temperatures below the hydrogen mobility (< 160 K) in charged irradiated specimens relaxation maxima are observed at 45, 100, 115 and 140 K which show no isotope shift for H and D charging. The maxima below 160 K are explained by defect-hydrogen complexes, where radiation-induced defects reorient around immobile hydrogen atoms. Above 160 K, where hydrogen atoms get mobile, in charged irradiated specimens a broad relaxation maximum appears at 170 K which shows an inverse isotope shift for H and D charging. This 170 K maximum anneals in Stage III. A hydrogen diffusion maximum observed in charged specimens at 215 K prior to irradiation is missing after electron irradiation. The 170 K relaxation is explained by defect-hydrogen complexes, where hydrogen atoms reorient around immobile radiation-induced defects while the long-range hydrogen diffusion is suppressed by these defects. In such relaxation measurements hydrogen and deuterium atoms are used as a “probe” to investigate radiation-induced defects.     

The bulk effect of point defects on young's modulus in electron irradiated copper

Abstract

Pairs of copper samples—one for electrical resistivity, the other for Young's modulus measurements - were irradiated simultaneously at 120°K with 3 MeV electrons up to an integrated dose of 2 × 10²⁰ el/cm². The effect of dislocation pinning and the bulk effect of point defects on Young's modulus E could clearly be separated. The following relation between the bulk effect ΔE/E and the resistivity increase Δρ[Ωcm] was found: ΔE/E = ?25 × 10⁴ × Δρ. Besides strong annealing in stages II and III (180–300°K) and some annealing between 300–500°K, stage V annealing (500–600°K) also was found. In stage III the resistivity annealed more than Young's modulus. whereas the converse occurred in stage V. These measurements are discussed in connection with the electron microsopical observation of point defect clusters after electron irradiation at 120°K and heating to room temperature.

Probenpaare, bestehend aus einer Widerstandsprobe und einer Probe zur Messung des Elastizitätsmoduls, wurden gleichzeitig bei 120°K mit 3 MeV-Elektronen bis zu einer Dosis von 2 × 10²⁰ el/cm² bestrahlt. Die direkte Reein-flussung des E-Moduls durch die im Gitter verteilten Punktdefekte (Volumeneffekt) konnte getrennt von der Beeinflussung durch Versetzungsverankerung gemessen werden. Es ergab sich dabei folgende Beziehung zwischen relativer Modulanderung ΔE/E und strahlungsinduziertem Widerstand Δρ[Ωcm]: ΔE/E = ?25 × 10⁴ × Δρ. Neben starker Erholung in den Stufen II und III (180–300 °K) und schwacher Erholung zwischen 300–500°K wurde auβerdem Stufe V (500–600°K) beobachtet. In Stufe III erholte sich der Widerstand starker als der E-Modul, wahrend in Stufe V das umgekehrte der Fall war. Die Messungen werden diskutiert in Zusammenhang mit der elektronenmikroskopischen Beobachtung von Punktdefektclustern nach Elektronenbestrahlung bei 120°K und anschlieβender Erwärmung auf Raumtemperatur.     

Adsorption of nitrogen on platinum

The adsorption and desorption of nitrogen on a platinum filament have been studied by thermal desorption techniques. Nitrogen adsorption becomes significant only after any carbon contamination is removed from the surface by heating the platinum filament in oxygen, and after the CO content in the background gas is reduced substantially. At room temperature nitrogen populates an atomic tightly bound β-state, E^≠ = 19 kcal mole^?1. The saturation coverage of the (3-state is 4.5 × 10¹⁴ atoms cm^?2. Formation of the (β-state is a zero order process in the pressure range studied. At 90 K two additional α₁- and α₂-desorption peaks are observed. The activation energy for desorption for the α₂-state is 7.4 kcal mole^?1 at low coverage decreasing to 3 kcal mole^?1 at saturation of this state, 6 × 10 molecules cm^?2. The maximum total coverage in the α-states was 1.2 × 10¹⁵ molecules cm^?2. A replacement process between the β- and α-states has been observed where each atom in the (β-state excludes two molecules from the α-state.     

Crystallinity and interdiffusion in InP/InGaAs quantum wells grown by Hydride VPE

This paper reports the results of a study on interfacial quality and thermal interdiffusion for InP/InGaAs Quantum Wells (QW) grown by hydride VPE. By controlling well layer as thin as 25 Å, it was estimated that island and valley, whose height was one monolayer and whose lateral size was one third of exciton radius, existed at the interface. For the first time, interdiffusion coefficients for InP/InGaAs QW were obtained from 77K PL peak energy shift. Typical values were 2.5×10⁻¹⁹ cm²/sec and 1.5×10⁻¹⁸ cm²/sec for the annealing temperature of 700°C and 750°C, respectively. These values are over 10² times larger than that in AlGaAs/GaAs QW, and less 10⁻² times smaller than that in InAlAs/InGaAs QW.     

Superior tolerance of Ag/Ni multilayers against Kr ion irradiation: an in situ study

Monolithic Ag and Ni films and Ag/Ni multilayers with individual layer thickness of 5 and 50?nm were subjected to in situ Kr ion irradiation at room temperature to 1 displacement-per-atom (a fluence of 2?×?10¹⁴?ions/cm²). Monolithic Ag has high density of small loops (4?nm in diameter), whereas Ni has fewer but much greater loops (exceeding 20?nm). In comparison, dislocation loops, ～4?nm in diameter, were the major defects in the irradiated Ag/Ni 50?nm film, while the loops were barely observed in the Ag/Ni 5?nm film. At 0.2?dpa (0.4?×?10¹⁴?ions/cm), defect density in both monolithic Ag and Ni saturated at 1.6 and 0.2?×?10²³/m³, compared with 0.8?×?10²³/m³ in Ag/Ni 50?nm multilayer at a saturation fluence of ～1?dpa (2?×?10¹⁴?ions/cm²). Direct observations of frequent loop absorption by layer interfaces suggest that these interfaces are efficient defect sinks. Ag/Ni 5?nm multilayer showed a superior morphological stability against radiation compared to Ag/Ni 50?nm film.     

Ni离子注入多晶ZrO2的表面电性能和结构

对氧化钇(Y₂O₃)部分稳定氧化锆(ZrO₂)样品在室温下进行了Ni离子注入(140kev,5×10¹⁵-2×10¹⁷ios/cm²)和热退火处理.应用电学测量,Rutherford背散射技术(RBS),X射线光电子能谱(XPS)和喇曼光谱方法研究了Ni离子注入多晶ZrO₂的表面电性能,注入层结构及其热退火的影响。     

Exchange of injected hydrogen isotopes between diffusing and trapped states in Al

Abstract

Exchange of hydrogen isotopes between diffusing and trapped populations was found with successive injections of 25 keV D₂ ⁺ and 100 or 140 keV H₂ ⁺ into Al surface by simultaneously detecting elastically recoilled hydrogen and deuterium using 2 MeV He⁺.

When backward diffusion of injected hydrogen toward surface was supposed to be impeded or by-passed by structural changes in the subsurface layer due to ion bombardment, effective replacement cross-section of about 1.4 × 10^?18 cm² was observed. Otherwise, namely when the hydrogen backward diffusion is supposed to be rather free, the effective cross section of about 7.8 × 10^?18 was observed.

Due to the difference in energy of the first and second injections, this phenomenon is different from that so called “isotopic exchange”, which occurs through collisional process.     

Effect of bombardment with iron ions on the evolution of helium,hydrogen, and deuterium blisters in silicon

The effect of bombardment with iron ions on the evolution of gas porosity in silicon single crystals has been studied. Gas porosity has been produced by implantation hydrogen, deuterium, and helium ions with energies of 17, 12.5, and 20 keV, respectively, in identical doses of 1 × 10¹⁷ cm^–2 at room temperature. For such energy of bombarding ions, the ion doping profiles have been formed at the same distance from the irradiated surface of the sample. Then, the samples have been bombarded with iron Fe¹⁰⁺ ions with energy of 150 keV in a dose of 5.9 × 10¹⁴ cm^–2. Then 30-min isochoric annealing has been carried out with an interval of 50°C in the temperature range of 250–900°C. The samples have been analyzed using optical and electron microscopes. An extremely strong synergetic effect of sequential bombardment of silicon single crystals with gas ions and iron ions at room temperature on the nucleation and growth of gas porosity during postradiation annealing has been observed. For example, it has been shown that the amorphous layer formed in silicon by additional bombardment with iron ions stimulates the evolution of helium blisters, slightly retards the evolution of hydrogen blisters, and completely suppresses the evolution of deuterium blisters. The results of experiments do not provide an adequate explanation of the reason for this difference; additional targeted experiments are required.     

Absolute coverages of CO and O on Pt(111); Comparison of saturation CO coverages on Pt(100), (110) and (111) surfaces

Nuclear microanalysis (NMA) has been used to determine the absolute coverages of oxygen and CO adsorbed on Pt(111). The saturation oxygen coverage at 300 K is 3.9 ± 0.4 × 10¹⁴ O atoms cm^?2 (θ = 0.26 ± 0.03), confirming the assignment of the LEED pattern as p(2 × 2). The saturation CO coverage at 300 K is 7.4 ± 0.3 × 10¹⁴ CO cm^?2 (θ = 0.49 ± 0.02). The low temperature saturation CO coverages on Pt(100), (110) and (111) surfaces are compared.     

高电子迁移率晶格匹配InAlN/GaN材料研究

文章基于蓝宝石衬底采用脉冲金属有机物化学气相淀积(MOCVD)法生长的高迁移率InAlN/GaN材料,其霍尔迁移率在室温和77 K下分别达到949和2032 cm²/Vs,材料中形成了二维电子气(2DEG). 进一步引入1.2 nm的AlN界面插入层形成InAlN/AlN/GaN结构,则霍尔迁移率在室温和77 K下分别上升到1437和5308 cm²/Vs. 分析样品的X射线衍射、原子力显微镜测试结果以及脉冲MOCVD生长方法的特点,发现InAlN/GaN材料的结晶质量较高,与GaN晶格匹配的InAlN材料具有平滑的表面和界面. InAlN/GaN和InAlN/AlN/GaN材料形成高迁移率特性的主要原因归结为形成了密度相对较低(1.6×10¹³-1.8×10¹³ cm^-2)的2DEG,高质量的InAlN晶体降低了组分不均匀分布引起的合金无序散射,以及2DEG所在界面的粗糙度较小,削弱了界面粗糙度散射. 关键词： InAlN/GaN 脉冲金属有机物化学气相淀积 二维电子气 迁移率     

Electrical transport measurements in a quasi-onedimensional semiconductor ZrS3

We have used the technique of chemical vapour transport to prepare needle shaped single crystal of ZrS₃. Results of the measurements of d.c. resistivity. Hall coefficient and thermoelectric power of the temperature range 100–500 K are reported. All the samples exhibited semiconducting behaviour with a room temperature resistivity of about 15 Ω-cm and an activation energy of 0.20±0.02 eV. Room temperature thermoelectric power is -850 μVK^?1 and the dominant carriers are electrons. The thermoelectric power varies as (1/T), a behaviour associated with a typical semiconductor. Mobility at low temperatures is limited by ionized impurity scattering and is given by μ₁ = 6.5 × 10^?2T^3/2 cm²V^7-1 sec^?1. At high temperatures, phonon scattering is dominant and the mobility is given by μ₂ = 1.35 × 10⁺⁵T^?32 cm²V^?1 sec^?1.     

New measurement of the elastic scattering cross section of μd muonic atoms off deuterons

We have measured the elastic scattering cross section for the process μd + d → μd + d in ultrapure gaseous deuterium at 14 atm and at room temperature. The results is σ_dd = (8 ± 2) × 10^?20 cm².     

Absolute coverage and isostemc heat of adsorption of deuterium on Pt(111) studied by nuclear microanalysis

The absolute coverage (θ) of deuterium adsorbed on Pt(111) in the ranges 180< T<440 K and 5 × 10^?6 < P < 5 × 10^?2 Pa D₂ has been determined by nuclear microanalysis using the D(³He, p)⁴He reaction. From these data, the isosteric heat of adsorption (E_a) has been determined to be 67 ± 7 kJ mol^?1 at θ ? 0.3. This heat of adsorption yields values of the pre-exponential for desorption (10^?5 to 10^?2 cm² atom^?1 s^?1) that lie much closer to the normal range for a second order process than those determined from previous isosteric heat measurements. The E_a versus θ relationship indicates that the adsorbed D atoms are mobile and that there is a repulsive interaction of 6–8 kJ mol^?1 at nearest neighbour distances. At 300 K the coverage decreases to ? 0.05 monolayer (? 8 × 10¹³ D atoms cm^?2) as P→ 0, apparently invalidating a recent model of site exchange in the adsorbed layer.     

Mössbauer study of the modification of iron during bombardment with deuterium at low temperature

Mossbauer spectra of a vacuum deposited 95 nm thick⁵⁷Fe film sandwiched between 35 nm copper layers on a beryllium substrate were measured during and after implantation with 60 keV D₃ ⁺ ions to a fluence of 1.2×10¹⁸ D⁺/cm². The modifications of the spectra indicate that at the target temperature of 100 K deuterium is mainly trapped at defects in the α-iron lattice or reemitted. Hydride formation is observed only weakly when the fluence exceeds 10¹⁸ D⁺/cm². After annealing at room temperature, a complete recovery of the ordinary α-iron spectrum is observed.     

Potassium adsorption on Fe(110)

LEED, AES, UPS and XPS were used to study submonolayer coverages of potassium on Fe(110). At room temperature the maximum potassium coverage is characterized by a LEED superstructure. This LEED pattern is interpreted as being due to a hexagonal close-packed K layer on Fe(110), resulting in a maximum atom density of 5.3 × 10¹⁴ cm^?2, i.e.θ k = 0.31. The work function change and the shift of the K(2p) and K(3p) core levels with potassium coverage indicate a charge transfer from potassium to iron at low potassium coverages.     

硫在镍(100)表面偏析动力学研究

本文使用AES-LEED联合装置研究了650—800℃温度范围内硫在镍(100)表面上的偏析动力学。结果表明,在较短退火时间内硫的表面浓度正比于退火时间的平方根,与McLean的动力学模型是一致的。扩散系数与温度的关系为D(cm²/s)=5×10^-3exp(-44600/RT)。硫偏析在镍(100)表面达到饱和值,LEED观察指出形成了硫的c(2×2)结构。深度剖面分析,硫/镍俄歇峰高比随氩离子剥离时间指数降低。 关键词：     

Hall effect in the natural glassy carbon of schungites

The temperature dependences (80–500 K) of the Hall coefficient and the resistivity of samples of schungite of types I and III (schungite I and schungite III), as well as a commercial glassy carbon, with carbon contents equal to 98, 30, and 99.99%, respectively, are measured. The character of the dependences of the resistivity and its numerical values are similar to those observed in polycrystalline graphites with a high degree of disorder and in synthetic glassy carbon. Conversely, the Hall coefficient in the schungite samples, as in high-quality single crystals and n-type intercalated compounds of graphite, is found to be negative, small in magnitude, and weakly dependent on the temperature. At room temperature it is equal to 2.83×10⁻²² and 0.305 cm³/C in schungite I and schungite III, respectively, the Hall mobility of the charge carriers in these materials is 8.0 and 9.2 cm²/V·s, and the Hall carrier concentration is 2.2×10²⁰ and 2.0×10¹⁹ cm⁻³. Fiz. Tverd. Tela (St. Petersburg) 39, 1783–1786 (October 1997)     

Simultaneous and sequential adsorption of deuterium and nitrous oxide by rhenium

The addition of nitrous oxide to a stream of deuterium passing over a rhenium filament reduced the initial sticking probability of the latter gas from 0.24 to 0.09 when the proportion of N₂O exceeded 40%. For the addition of deuterium to nitrous oxide the equivalent figures were 0.45 and 0.30 when deuterium exceeded 30% of the gas phase. These results are attributed to a competition between the two gases for places in the precursor state on the surface. The replacement of adsorbed deuterium from a saturated layer by the oxygen atom of nitrous oxide proceeded initially with a high probability, 0.27, at room temperature and with each oxygen atom replacing one deuterium atom. However, the reaction was incomplete, about 2 × 10¹⁴ atoms cm^?2 of deuterium remaining on the surface. It is suggested that kinetic rather than thermodynamic factors are responsible for the incomplete reaction, possibly as the result of a high activation energy for the migration of deuterium atoms over an oxygenated rhenium surface.     

The transport properties of Dirac fermions in chemical vapour-deposited single-layer graphene

Abstract

The electronic transport properties of Dirac fermions in chemical vapour-deposited single-layer epitaxial graphene on anSiO₂/Si substrate have been investigated using the Shubnikov–de Haas (SdH) oscillations technique. The magnetoresistance measurements were performed in the temperature range between 1.8 and 43 K and at magnetic fields up to 11 T. The 2D carrier density and the Fermi energy have been determined from the period of the SdH oscillations. In addition, the in-plane effective mass as well as the quantum lifetime of 2D carriers have been calculated from the temperature and magnetic field dependences of the SdH oscillation amplitude. The sheet carrier density (1.42 × 10¹³ cm^?2 at 1.8 K), obtained from the low-field Hall Effect measurements, is larger than that of 2D carrier density (8.13 × 10¹² cm^?2). On the other hand, the magnetoresistance includes strong magnetic field dependent positive, non-oscillatory background magnetoresistance. The strong magnetic field dependence of the magnetoresistance and the differences between sheet carrier and 2D carrier density can be attributed to the 3D carriers between the graphene sheet and the SiO₂/Si substrate.     

Temperature-dependent luminescence of GaAs doping superlattices

The photon energy of the luminescence between spatial separated n- and p-type doped layers of GaAs doping superlattices shifts with excitation density. At room temperature we observe a shift of the luminescence maximum in samples with high doping concentrations (n=4×10¹⁸cm⁻³), whereas for n=1×10¹⁸cm⁻³ this shift is observed at temperatures below 150K only. Temperature-dependent measurements between 4 and 700K show that the tunability disappears near a critical temperature, which is proportional to the doping concentration. A simple model including thermally activated direct transitions and tunable luminescence describes this temperature dependence.