Formation of nanotubes in Cz Si wafers using He+ implantation and subsequent O+- or N+-plasma treatment

Standard 4.5 Ω cm n-type and 12 Ω cm p-type Cz Si wafers were implanted with helium ions of 300 keV energy and the fluences of 1 × 10¹⁵, 5 × 10¹⁵, 1 × 10¹⁶ or 2 × 10¹⁶ at/cm² at room temperature. The implanted wafers were then annealed in vacuum at 650, 700, 750 or 800 °C. Then oxygen or nitrogen ions of the fluence of 2 × 10¹⁷ cm^?2 were introduced to the silicon wafers from a plasma source followed by annealing the samples in vacuum at 900 °C.The structural properties of the samples were investigated using SEM. To control the treatment's influence on the electrical properties of the wafers, the measurements of charge carriers' lifetime were carried out.1D defects (nanotubes) normal to the sample surface with defect's length equal to the projected range of the implanted ions were formed in the Cz Si wafers following He⁺ implantation with subsequent vacuum annealing and plasma treatment. The surfaces of wafers contained a small density of defects.     

The absolute detection efficiency of vacuum electron multipliers,to keV protons and Ar+ ions

The single-ion detection efficiency of two types of electron multipliers is provided for incident energies reaching 10 keV. Absolute efficiencies above 90% were measured for a discrete dynode electron multiplier (DDEM), in response to Ar⁺ ions and protons, above an energy of 5 keV. The efficiency to detect protons is consistently higher than that of Ar⁺ ions, due to a higher secondary electron emission yield. For a channel electron multiplier we have measured a similar maximal detection efficiency for Ar⁺ ions; though strongly varying across the detector surface.     

The electromagnetic response of the heavy electron superconductor URu2Si2

We report measurements of the surface resistance and skin depth in single crystals of the heavy electron superconductor URu₂Si₂. The measurements were made in all-copper helical resonators in the frequency range 0.19 GHz to 0.54 GHz with the ac fieldB a-axis and the induced current,J, alternately along the a- and c-axes. The surface resistance appears to exhibit the nonexponential behavior expected for a heavy electron superconductor; however, the behavior of the skin depth is more anomalous: The ac magnetic field penetrates more deeply into the superconducting sample at higher frequencies.     

The combined use of He back-scattering and He-induced X-rays in the study of anodically grown oxide films on GaAs

Anodic oxide films on GaAs have been studied by the combined use of He back-scattering and He-induced X-rays. Back-scattering is hampered by the lack of mass resolution between Ga and As. X-ray analysis has excellent mass resolution but poor depth resolution. This poor depth resolution is overcome by increasing the effective thickness of the films by entering at grazing angles and making use of the property that the He-induced X-ray cross sections fall steeply with decreasing energy. This technique and the methods of data analysis are discussed in detail. The anodic oxide films are found to be deficient in As within 200 Å of the surface and to have a Ga:As ratio of approximately 1:1 for the rest of the oxide. On heating to 650°C most of the As diffuses out of the films.     

Effect of Si and He implantation in the formation of ultra shallow junctions in Si

He, Si and B implantation are successively combined in order to produce ultra shallow junctions (USJs). Si is implanted at 180 keV to create a ‘vacancy-rich’ layer. Such a layer is however followed by a deeper interstitial rich one. He implantation is performed at a dose high enough (5 × 10¹⁶ cm^− 2) to create a cavity layer in Si sample. Eventually, B is introduced by low energy ion implantation. Since cavities are known to be sinks for self-interstitials (Is), they might be able to decrease the transient enhanced diffusion (TED) of B during the dopant activation annealing in all processes investigated in this study. The samples are divided in two groups (named S1 and S2) to check the benefits of defect engineering of each implantation element. Hence, sample 1 is first implanted with He, followed by cavity formation annealing and second with B. Si implantation is performed on S2 after cavity formation, and followed by B implantation in the same condition as S1. All samples are characterized by secondary ion mass spectrometry (SIMS), transmission electron microscopy (TEM) and Hall effect measurements. Results show that, in all cases, boron TED is suppressed while working with a cavity layer created before activation annealing. This layer acts as an Is barrier. Finally, an USJ with a low junction depth (X_j = (13 ± 1) nm, determined at 10¹⁸ cm^− 3 boron level) is successfully realized.     

Study of radiation resistance to helium swelling of AlN ceramics in case of irradiation with low-energy He2+ ions with energy of 40 keV

Journal of Materials Science: Materials in Electronics - In recent years, ceramic materials based on nitrides are of particular interest, which have great potential to be used as the basis of...     

Swift heavy ion induced formation of nanocolumns of C clusters in a Si based polymer

The formation of nanocolumns of C clusters in thin films of a Si based inorganic polymer, allylhydridopolycarbosilane (HPCS), as a result of irradiation of the films with 100?MeV Au ions at fluences of 2 × 10(12) and 5 × 10(12)?ions?cm(-2) is demonstrated. The evolution and arrangement of the C?clusters while subjected to the irradiation fluence is investigated by energy filtered cross-sectional transmission electron microscopy. Irradiation results in evolution of C clusters of sizes ≤5?nm, and their alignment along channels of ～10?nm diameter, which are essentially the latent tracks created by the Au ions in the polymer. At the fluence of 5 × 10(12)?ions?cm(-2), these clusters become densely packed in the channels. The growth of such C cluster filled nanocolumns is shown to be a consequence of two simultaneous diffusion processes taking place during the transient molten phase of the latent tracks.     

The interaction of magnesium in hydration of C3S and CSH formation using 29Si MAS-NMR

Hydration of tricalcium silicate in hydrothermal conditions in the presence of magnesium oxide has shown changes in the formation of CSH gel structure (Calcium silicate hydrates). The new CSH incorporates magnesium ions, brucite, but a weak presence of portlandite. The magnesium oxide would hinder the precipitation of portlandite. The characterization of CSH gel by ²⁹Si MAS-NMR with various CaO/SiO₂ ratios would point out that: (1) A dreierketten structure of the CSH for low CaO/SiO₂ < 1, with some defects (Q³ defect and Q^2v) in its structure is confirmed. Some magnesium ions are incorporated in the octahedral sites, in the interlayer space of the dreierketten pattern. (2) For the CSH gels with CaO/SiO₂ ratios > 1, magnesium ions would be incorporated in the silicate chains of the CSH gel in a tetrahedral coordination. Although, the low MgO/CaO ratios of CSH gels indicate that the magnesium incorporation in CSH chain is low.     

密封器件压氦和预充氦细检漏过程中环境氦分压的影响

分别推导和分析了环境大气氦分压对压氦法的影响,地球干洁大气氦分压对预充氦法和预充氦密封器件压氦法复检的影响.证明对于压氦法,不需要考虑地球干洁大气氦分压的影响.但是如果候检室环境大气氦分压显著升高,对于内腔有效容积大,且等效标准漏率小的密封器件,会加大测量漏率值,所以压氦后,被检器件应尽快离开压氦设备所在的房间.对于预充氦法,地球干洁大气氦分压会使测量漏率通过极大值后出现极小值,且当候检时间与内腔有效容积之比大于100 h/cm3时,极小值点的气流仍处于分子流状态,不能靠粗检鉴别,所以需压氦法复检加粗检,才能防止漏检.另外,地球干洁大气氦分压会使预充氦法候检时间的第一特征点变大,从而扩大了需压氦法复检加粗检的范围,但第二特征点不变,也不影响压氦法复检加粗检的结果.     

The detection of rare earth impurities in ionic materials by X-ray-stimulated luminescence

The application of X-ray-stimulated luminescence to the detection of trivalent rare earth impurities in ionic materials is discussed. Characteristic luminescent wavelengths allow the identification of individual rare earths. The lower limit of impurity detectable in the particular case of the fluorides is found to be about 0.01 ppm if no positive identification of the rare earth ion is required. This is increased to 1 ppm when positive identification of the specific impurity is required. The application of the technique to the assessment of single crystals and the appropriate starting material is discussed.     

Transport properties under magnetic fields of the heavy fermion system CeRu2Si2 and related compounds (Ce,La)Ru2Si2

Measurements of thermoelectric power (TEP) and thermal conductivity of single crystals CeRu₂Si₂ and Ce_1–x La _x Ru₂Si₂ are reported with special emphasis on the effect of the magnetic field. The roles of the crystal electric field splitting and the Kondo effect on TEP curves are debated. The TEP results at low temperature are analyzed with a two-band model, and the parameters are compared with those extracted from the thermodynamic measurements. In CeRu₂Si₂ the occurrence of a coherent regime at very low temperature discussed. The influence of the magnetic field on the TEP and the thermal conductivity is investigated and related with the occurrence of the metamagnetic-like transition already reported in magnetization measurements.     

Processes of Charge State Change at Collisions of He2+ and ArZ+ Ions with Fullerenes

Using coincidence technique the relative cross-sections of charge state change and fragmentation at one and two electron capture processes have been measured for the first time at collisions of He²⁺ and Ar^z+ projectiles with fullerenes in the energy range (3-35)z keV.     

Processes of Charge State Change at Collisions of He2+ and ArZ+ Ions with Fullerenes

Abstract

Using coincidence technique the relative cross-sections of charge state change and fragmentation at one and two electron capture processes have been measured for the first time at collisions of He²⁺ and Ar^z+ projectiles with fullerenes in the energy range (3-35)z keV.     

The effect of He or Ar/O2 plasma treatment on Si surface prior to chemical vapor deposition of SiO2

The effect of O₂ plasma pretreatment on the SiO₂/Si interface property was studied using direct plasma varying the plasma power, He or Ar/O₂ ratio and the pretreatment time. The decrease of the pretreatment plasma power decreased the plasma damage and improved the interface property. The addition of He in O₂ glow discharge improved the electrical and the interface properties and there was an optimum He/O₂ ratio. The improvement of the interface property by Ar/O₂-plasma pretreatment was better than that by He/O₂, which is believed to be due to the lower oxidation rate of the Si surface. C–V analysis showed that the P_b center defect density was influenced by plasma pretreatment process parameters. To investigate the oxidation states near to and at the SiO₂/Si interface, X-ray photoelectron spectroscopy depth analysis was used and the gas phase in the glow discharge was investigated using optical emission spectroscopy analysis at various experimental conditions.     

Enhancement of immunoassay's fluorescence and detection sensitivity using three-dimensional plasmonic nano-antenna-dots array

Protein detection is universal and vital in biological study and medical diagnosis (e.g., cancer detection). Fluorescent immunoassay is one of the most widely used and most sensitive methods in protein detection (Giljohann, D. A.; Mirkin, C. A. Nature2009, 462, 461-464; Yager, P.; et al. Nature2006, 442, 412-418). Improvements of such assays have many significant implications. Here, we report the use of a new plasmonic structure and a molecular spacer to enhance the average fluorescence of an immunoassay of Protein A and human immunoglobulin G (IgG) by over 7400-fold and the immunoassay's detection sensitivity by 3,000,000-fold (the limit of detection is reduced from 0.9 × 10(-9) to 0.3 × 10(-15) molar (i.e., from 0.9 nM to 300 aM), compared to identical assays performed on glass plates). Furthermore, the average fluorescence enhancement has a dynamic range of 8 orders of magnitude and is uniform over the entire large sample area with a spatial variation ±9%. Additionally, we observed that, when a single molecule fluorophore is placed at a "hot spot" of the plasmonic structure, its fluorescence is enhanced by 4 × 10(6)-fold, thus indicating the potential to further significantly increase the average fluorescence enhancement and the detection sensitivity. Together with good spatial uniformity, wide dynamic range, and ease to manufacture, the giant enhancement in immunoassay's fluorescence and detection sensitivity (orders of magnitude higher than previously reported) should open up broad applications in biology study, medical diagnosis, and others.     

Thickness effect on the formation of SiC nanoparticles in sandwiched Si/C/Si and C/Si multilayers

The effect of carbon (C) and amorphous silicon (a-Si) thicknesses on the formation of SiC nanoparticles (np-SiC) in sandwiched Si/C/Si and C/Si multilayers on Si(100) substrates were investigated using ultra-high-vacuum ion beam sputtering system and vacuum thermal annealing at 500, 700, 900 °C for 1.0 h. Three-layer a-Si/C/a-Si structures with thicknesses of 50/200/50 nm and 75/150/75 nm and a two-layer C/a-Si structure of 200/50 nm were examined in this study. The size and density of np-SiC were strongly influenced by the annealing temperature, a-Si thickness and layer number. Many np-SiC appeared at 900 °C at a density order about 10⁸ cm^− 2 in both three-layer structures while no particles formed in the two-layer structure. The thick a-Si structure (75/150/75 nm) produces a particle density approximately 1.8 times higher than thin structure (50/200/50 nm). This implies that thick a-Si structure had a lower activation energy of SiC formation compared to the thin a-Si structure. Few particles were found at 700 °C and no particles at 500 °C in both three-layer structures. The np-SiC formation is a thermally activated reaction. The higher temperature leads to higher particle density. A mechanism of np-SiC formation in thermodynamic and kinetic viewpoints is proposed.     

Influence of various divalent impurities on dislocation density in KCl:Mg2+, Ca2+, Sr2+ or Ba2+ single crystals

Single crystals of nominally pure KCl and KCl doped with Mg²⁺, Ca²⁺, Sr²⁺ or Ba²⁺ were deformed by compression at 77–254 K; during the tests strain-rate cycling was conducted in association with ultrasonic oscillation. The data were analyzed in terms of strain-rate sensitivity ((/ln)) versus stress decrement (). The curve for KCl doped with the divalent impurities has two bending points and two plateau regions. It is proposed that the variation of strain-rate sensitivity at the second plateau place on the curve with shear strain ((/ln)/) is due to a change in forest dislocation density with shear strain. The forest dislocation density for the specimens seemed to increase by the divalent additions in the compression test on account of the jogs on the screw dislocations. It depended on the concentration of impurities and also on the size of impurity in the specimens at a given temperature. Unfortunately, it was not possible to determine whether a change in the size of impurity influences mobile dislocation density, , from the values of / for KCl doped with Ca²⁺, Sr²⁺ or Ba²⁺.     

中心切割气相色谱分析烃类气体中微量烃类杂质

利用多维色谱的中心切割技术与三氧化二铝毛细柱配合检测烃类气体中的烃类杂质,此法也适于检测高浓度气体中的微量杂质     

Diffusion of Mn2+ impurities in alkali halides and its influence in epitaxy phenomena

A previous paper reported that Mn²⁺ impurities contained in NaCl tend to migrate from the volume to the surface when the crystals are heated to temperatures between 400° and 550°C in air. Once on the surface, the impurities react with oxygen and an epitaxial oxide film is produced on the NaCl substrate. In the present work new data about this oxide film are reported. It has been found that diffusion to the surface can also be observed for KCl:Mn²⁺, LiF:Mn²⁺ and LiCl:Mn²⁺ crystals, at several impurity concentrations, and when heating is carried out in a vacuum of 10^-6 torr. It is shown that this effect has a strong influence in the epitaxy of metal films on alkali halide substrates.