Spectrum Simulation of Li-Like Aluminium Plasma

X-ray emission spectra for L-shell of Li-like aluminium ions are simulated by using the flexible atomic code based on the collisional radiative model. Atomic processes including radiative recombination, dielectronic recombination, collisional ionization and resonance excitation from the neighbouring ion （Al^9＋ and Al^11＋ ） charge states of the target ion （Al^10＋） are considered in the model. In addition, the contributions of different atomic processes to the x-ray spectrum are analysed. The results show that dielectronic recombination, radiative recombination, collisional ionization and resonance excitation, other than direct collisional excitation, are very important processes.     

Magnetic susceptibility and magnetic resonance study of acceptor doped fullerenes C60(MF6)2 (M=As, Sb, P)

In order to check whether superconductivity occurs in the acceptor doped fullerenes C₆₀(MF₆)₂ (M=As, P, Sb) and to study their magnetic and structural properties, we have carried out magnetic, EPR and NMR measurements of these compounds. Temperature dependences of magnetic susceptibility down to 5 K and field dependences of magnetic moment at 5 K show no ‘bulk’ transition in superconducting state. Some reasons of the absence of superconductivity, such as insufficient charge transfer between C₆₀ and intercalated species and inhomogeneity of the compounds under study, are discussed.     

MXene-碳黑/硫复合材料在锂硫电池一体式电极的研究

锂硫电池的实际能量密度不高和多硫化物（LiPSs）的穿梭效应等问题严重影响了该电池的实际应用。本文通过将二维的Ti₃C₂T_x Mxene纳米片与碳黑/硫（CB/S）材料进行混合,制备了Ti₃C₂T_x-CB/S正极材料并将其涂覆在商业隔膜（PP）上,最终获得了Ti₃C₂T_x-CB/S-PP一体式电极并用于锂硫电池。利用Ti₃C₂T_x纳米片对CB/S进行修饰,不仅能提高活性物质硫的导电性,还能对扩散的LiPSs进行物理阻挡和化学吸附。而一体式电极的设计有利于提高电池的能量密度。恒流充放电测试结果表明,Ti₃C₂T_x-CB/S-PP电极在0.1 C电流下的初始放电容量为1028.8 mAh·g^-1,高于不含Ti₃C₂T_x的CB/S-PP电极的896.8 mAh·g^-1。Ti₃C₂T_x-CB/S-PP电极还展示出了比基于传统铝箔集流体的Ti₃C₂T_x-CB/S-Al电极更好的循环稳定性,前者在0.5 C下400圈长循环测试中的每圈衰减率为0.072%,而后者则为更高的0.10%。本文利用Ti₃C₂T_x-CB/S构建一体式电极的策略为实现高性能和高能量密度的锂硫电池提供了新的研究方向。     

Simultaneous Delamination and Rutile Formation on the Surface of Ti3C2Tx MXene for Copper Adsorption

In this work, we studied the formation of the rutile phase of titanium dioxide (TiO₂) on delaminated MXene (d‐Ti₃C₂T_x) flakes by the reaction of Ti₃C₂T_x with amino acids in water. Three types of amino acids with varied side‐chain polarity were used to delaminate Ti₃C₂T_x. d‐Ti₃C₂T_x flakes formed stable colloidal solutions due to the negative surface charges of chemisorbed amino acids on the d‐Ti₃C₂T_x. Rutile formed on d‐Ti₃C₂T_x at room temperature upon the intercalation of aromatic amino acids and subsequent sonication of the solution, while flakes intercalated with aliphatic amino acids did not oxidize. X‐Ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy revealed the nanosize rutile formation on the surface of Ti₃C₂T_x flakes. The XPS results indicated the surface functionalization of histidine on d‐Ti₃C₂T_x flakes. As‐synthesized histidine functionalized rutile TiO₂@d‐Ti₃C₂T_x hybrid was used for adsorption of Cu²⁺ ions from aqueous solution with a maximum uptake of 95 mg g^?1.     

Debye series expansion of shaped beam scattering by GI-POF

We derive Debye series expansion (DSE) for infinitely long multilayered cylinders normally incident by shaped beam. Typically the interaction between multilayered cylinders and Gaussian beam is derived in detail, and localized approximation is introduced to calculate the beam shaped coefficients. Finally DSE is employed to the study of rainbow scattering by graded-index polymer optical fiber (GI-POF).     

Optimized 3D structures and energy bands of peanut-shaped C60 polymers

Optimized three-dimensional (3D) cell structures and energy bands of fused (peanut-shaped) C₆₀ polymers (p55 and p66) have been investigated using the first-principles pseudopotential approach within the local density approximation of the density functional theory. We found that the resulting electronic structure is either metal or semiconductor depending on the shape of the polymer chains and the unit cell structure.     

Microscopic growth mechanisms for carbon and boron-nitride nanotubes

Received: 27 November 1998 / Accepted: 18 December 1998     

X-ray and UV photoelectron spectroscopy study of Na-halogen-graphite intercalation compounds. Comparison between donor- and acceptor-graphite compounds

New results obtained with XPS and UPS on ternary Na-halogen-graphite intercalation compounds (GICs) complement previous ones obtained on binary alkali- and ternary alkali-oxygen-GICs yet published, to give a general overview about what can be learned from photo-electron spectroscopy. In addition to surface stoichiometry, the charge transfer, the Fermi level energy shift and the band structure are estimated thanks to the observation in UP spectra of the unoccupied Π^∗ level peak.     

Electronic structure of solid C48N12 aza-fullerene

I report electronic structures and the cohesive energy for face-centered-cubic (fcc) solid C₄₈N₁₂ using generalized-gradient density-functional theory. The full vibrational spectrum of the C₄₈N₁₂ cluster is calculated within the harmonic approximation at the B3LYP/6-31G* level of theory. The results show that fcc is energetically preferred and a more stable crystal form than body-centered-cubic (bcc). C₄₈N₁₂ clusters are found to condense by a weak (0.29 eV) van der Waals force. The band gap of fcc C₄₈N₁₂ is calculated to be 1.3 eV at the GGA-PW91 level, whereas the HOMO-LUMO gap is calculated to be 2.74 eV using B3LYP/6-31G*.     

Modeling of Cu gettering in p- and n-type silicon and in poly-silicon

Based on experimental findings we set up calculations of numerical modeling of gettering efficiencies for Cu in various silicon wafers. Gettering efficiencies for Cu were measured by applying a reproducible spin-on contamination in the 10¹² atoms/cm² range, followed by a thermal treatment to redistribute the metallic impurity. Subsequently, the wafers were analyzed by a novel wet chemical layer-by-layer etching technique in combination with inductively coupled plasma mass spectrometry. We investigated p/p+ and n/n+ epitaxial wafers with different doping levels and different substrate-doping species. We have also investigated gettering efficiencies of phosphorus-diffused p- and n-type wafers. Heavilyboron doped silicon exhibited a gettering efficiency of ∼100%, while gettering by n+ silicon occurred for doping levels >3×10¹⁹ atoms/cm³ only. In another set of experiments we investigated the dependence of the gettering efficiency of p-type wafers with poly-silicon back sides for different cooling rates and Cu spiking levels. A strong dependence on both parameters was found. Cu gettering in p/p+ epitaxial wafers was modeled by calculating the increased solubility of Cu in p+ silicon compared to non-doped silicon taking into account the Fermi-level effect, which stabilizes donors in p+ silicon, and the pairing reaction between Cu and B. Calculated gettering efficiencies were in very good agreement with experimental results. Gettering in n+ silicon was similarly modeled in terms of pairing reactions and the Fermi-level effect. But, for n-type silicon, many experimental uncertainties existed; thus, we applied our expressions to solubility data of Hall and Racette to obtain the unknown parameters. The empirical calculations were in good agreement even with results on n/n+ wafers. For phosphorus-diffused wafers we had to consider an excess vacancy concentration of 1.2–5.5 times the equilibrium concentration to explain the experimental findings by the model. Gettering by poly-silicon back sides was simulated by solving the time-dependent diffusion equation with boundary conditions that take into account different surface reaction rates of silicon point defects. Using this advanced model, the experimentally measured gettering efficiencies were reproduced within the uncertainty of the measurement. Received: 3 September 2001 / Accepted: 4 September 2001 / Published online: 20 December 2001