Determination of the nonequilibrium concentration of vacancies in silicon crystals by measuring the concentration of nickel atoms at lattice sites

A method is proposed for determining the nonequilibrium concentration of vacancies and vacancy complexes in silicon crystals by measuring the concentration of electrically active nickel atoms at the sites of the silicon lattice, [Ni _s ], after the diffusion of nickel at temperatures from 550 to 650°C. It is shown experimentally that, after the diffusion of nickel from the surface into silicon samples with different initial nonequilibrium concentrations of vacancy complexes, [V]_init, formed during crystal growth, the concentration [Ni _s ] in the bulk of a sample to a good degree of accuracy corresponds to the vacancy concentration [V]_init determined by a standard method based on the analysis of the concentration profiles of [Au _s ] after the diffusion of gold from the surface. This method for determining the concentration of vacancies is much simpler than the standard method and allows one to use lower temperatures and a lower thermal budget.     

Determination of the Avogadro constant by counting the atoms in a 28Si crystal

The Avogadro constant links the atomic and the macroscopic properties of matter. Since the molar Planck constant is well known via the measurement of the Rydberg constant, it is also closely related to the Planck constant. In addition, its accurate determination is of paramount importance for a definition of the kilogram in terms of a fundamental constant. We describe a new approach for its determination by counting the atoms in 1 kg single-crystal spheres, which are highly enriched with the 28Si isotope. It enabled isotope dilution mass spectroscopy to determine the molar mass of the silicon crystal with unprecedented accuracy. The value obtained, NA = 6.022,140,78(18) × 10(23) mol(-1), is the most accurate input datum for a new definition of the kilogram.     

Determination of the photoionization threshold of the deep donor in Al0.33Ga0.67As:Si

Photoionization of the DX center in Si-doped A1_0.33Ga_0.67As has been studied by means of photoconductivity. The optical cross-section _nd ⁰ shows a threshold at=200 meV and relative maxima (shoulders) around 400, 600, 950, and 1700 meV. The results throw doubt on the validity of the large lattice relaxation model, generally accepted for this class of centers. They can be well accounted for by the small relaxation model, recently proposed by the authors.     

A high resolution investigation of the recombination radiation from Si containing the acceptors B,Al, Ga,In and Tl

A high resolution investigation has been made of the luminescence from Si doped with the acceptors B, Al, Ga, In and Tl in the spectral energy range 0.96–1.16 eV using 50 keV electron excitation. Luminescence from Tl-doped material has not previously been reported. Particular attention is directed to the splitting of the no-phonon and phonon-assisted bound exciton lines which has been detected for the first time in luminescence studies. Thermalizing doublet structure has been observed for Al, Ga and In-doped Si and a thermalizing triplet structure for tl-doped material, and three possible models for the fine structure are considered. Satellite lines on the low energy side of the bound exciton lines, which have previously only been observed in B, P and Li-doped Si and attributed to multiple bound exciton complexes, are reported for Al and Ga-doped material. Recent models for these lines are discussed together with their relationship with electron-hole droplet condensation. Structure associated with free electron to bound hole transitions are reported and discussed.     

ICP-AES测定Beta沸石分子筛中的Si和Al

研究了Beta沸石分子筛中Si、Al元素的ICP-AES分析方法，考察了溶液中酸度、高频功率、积分时间对测定的影响，以及共存元素间的相互干扰及干扰的校正方法。优化了工作条件，方法的相对标准偏差均小于5％，回收率为98％-105％。     

燃料油中钒、铝、硅元素的准确测定

本文提出了利用程序升温来缓慢灰化燃料油样品的方法，避免了传统灰化法因不完全燃烧引起的含量损失及重复性差的问题。     

Effect of air on the concentration of molecular hydrogen in the conversion of ethanol by a nonequilibrium gas-discharge plasma

The effect of air on the concentration of molecular hydrogen in the conversion of ethanol by a nonequilibrium gas-discharge plasma is theoretically studied. Two models are developed to calculate plasma kinetics in two operation regimes of an experimental setup used for ethanol conversion into free hydrogen in order to increase the efficiency of the combustion of heavy hydrocarbon fuels. A comparison with the experimental results demonstrates that both of the models adequately describe the kinetics of the discharge reactions.     

硅铁中Si,Al,Ca,Mn,Cr,P和S元素的X射线荧光光谱分析

叙述了用ＡＲＬ８４８０型Ｘ射线荧光光谱仪测定硅铁中Ｓｉ、Ａｌ、Ｃａ、Ｍｎ、Ｃｒ、Ｐ和Ｓ元素的Ｘ射线荧光光谱分析方法。采用直接粉末压片法制样。分析结果与化学法结果相符。方法快速、准确、经济、简便，精密度很好。通常，结果是令人满意的     

Unambiguously distinguishing Si[3Si,1Al] and Si[3Si,1OH] stuctural units in zeolite by 1H/29Si/27Al triple resonance solid state NMR spectroscopy

We present an experimentally feasible triple-resonance NMR method that establishes the correlation among three different nuclei, avoiding the difficulty to directly explore the weak coupling between two NMR nuclei, such as (29)Si and (27)Al. Using this method, we are able to give an unambiguous assignment to the various peaks in (29)Si CP NMR spectrum of MCM-22 zeolite and discriminate (29)Si signals from SiOHAl and SiOH groups. In addition, in combination with (1)H/(27)Al double-resonance technique, the (1)H/(27)Al/(29)Si triple-resonance experiment suggests the presence of two different kinds of Br?nsted acid sites in H-MCM-22 zeolite.