Improvement in quantitative correction in SIMS using Saha-Eggert equation

Summary Improvement in Quantitative Correction in SIMS Using Saha-Eggert Equation A quantitative conversion of the secondary-ion current intensities into the elemental concentrations using the Saha-Eggert ionization equation was tried with a 78Ni-18Cr-1Ti-1Fe-1Cu-1Zr (each in at %) alloy. Improvements were made on the best-fit search of fitting parameters (T andN _e). It proved to be important for the success in the conversion (1) to use the secondary-ion intensities from the sample in oxygen gas of >1.5×10^–3 Pa, (2) to add the molecularion intensities to those of mother atomic ions even when the former are small and (3) to search for the fitting parameters considering the relative errors of concentrations not only for the internal standards but for as many elements as possible. With these procedures the largest error of elemental concentration could be reduced to 22% (Ar⁺ bombardment), 31% (O₂ ⁺ bombardment) and 19% (N₂ ⁺bombardment).A part of this paper was presented at the 4th International Conference on Secondary Ion Mass Spectrometry, Osaka, November 1983.     

Difference between chemical structures of the interface at the Al-oxide tunneling barrier prepared by plasma or by radical oxidation

We have studied chemical structures of the interface between the Al-oxide tunneling barrier and the underlying Co₉₀Fe₁₀ layer in magnetic tunnel junctions when a 1-nm thick metallic Al barrier was oxidized by two different methods: plasma oxidation and radical oxidation. Our chemical analyses confirmed that the underlying CoFe layer was unavoidably attacked by oxygen during the oxidation and that this left different oxide states at the AlO_x/CoFe interface, depending on the oxidation method. The radical oxidation required long oxidation time for optimizing tunneling performance and resulted in a large amount of oxygen at the interface, which, in turn, resulted in the formation of mostly α-Fe₂O₃ and Al₂O₃. Conversely, the plasma oxidation required a relatively short oxidation time for optimization and left FeO as a dominant phase at the interface. Our results also show that the thermal treatment helped AlO_x, an oxygen-deficient phase, to be re-oxidized and transformed into Al₂O₃, the thermodynamically stable stoichiometric phase. The oxygen that diffused from the reduced CoFe layer into the barrier is likely responsible for this oxygen enrichment. We show that such differences in the chemical structure of the interface are critical clues to understanding what causes the change in tunneling properties of magnetic tunnel junctions.     

XPS study of the phase transition in pure zirconium oxide nanocrystallites

Pure zirconium oxide nanocrystallites with diameters 6-140 nm are fabricated from ultrafine metallo-organic complexes by thermal hydrolysis at 120 °C and/or heat treatment at 125-1025 °C. X-ray photoelectron spectroscopy shows that effective ionic valence of Zr decreases with decreasing particle diameter. The size dependence of the ionic valences suggests that the phase transition from cubic to tetragonal occurs at an effective Zr valence of 2.0 near 3 nm in diameter and that the phase transition from tetragonal to monoclinic takes place at a critical size of 25 nm diameter with an effective Zr valence of about 2.6.     

Trends of optically fed wireless communication systems

Mobile communication systems such as cellular radio and PHS are rapidly penetrating into our real life, and have gained many subscriber numbers. User demands will be growing to higher data rates that support multimedia mobile computing demands, such as graphics and motion pictures. These demands require more band width and/or spectrum utilization efficiency enhancement, and optically fed communication systems are considered to be one of the most powerful solutions. In this paper, the roles, technologies and application examples of optically fed communication systems are described. In the final part, prospects for systems and requirements for photonic devices are mentioned.     

Selective synthesis of 1,4,5-trisubstituted imidazoles from α-imino ketones prepared by N-heterocyclic-carbene-catalyzed aroylation

An alternative synthetic route to 1,4,5-trisubstituted imidazoles from α-imino ketone, which can be prepared from imidoyl chlorides and aromatic aldehydes via N-heterocycle carbene-catalyzed aroylation was developed. This methodology consists of simple transformations, allowing a rapid access to imidazole derivatives with various aryl substituents at the desired positions.     

Synthesis and spectrophotometric study of 2-[2-(3,5-dibromopyridyl,)azo] -5-dimethylaminobenzoic acid as an analytical reagent: Determination of nickel

2-[2-(3,5-Dibrornopyridyl)azo]-5-dimethyIam;nobenzoic acid (3,5-diBr-PAMB) has been synthesized and its potential for the spectrophotometric determination of metals studied. It reacts sensitively with nickel, cobalt, iron and copper, and is particularly useful for nickel. The apparent molar absorptivity in chloroform is 1.50 × 10⁵ l mol^-1 cm^-1 and the Sandell sensitivity is 0.4 ng Ni cm^-2. Nickel reacts with 3.5-diBr-PAMB at pH 4–10; at pH 4–7 the complex can be extracted into chloroform to give a stable purple solution. The optimal calibration range is 0.04–0.4 ppm Ni. Only Cu, Co, Fe, Pd and V interfere seriously but Pd, Cu and V can be masked by thiourea.     

Hydrogen atom abstraction and electron transfer of triplet 2,3-dihalo-1,4-naphthoquinones studied by the cidep technique and laser flash photolysis

Investigations using CIDEP techniques showed that an H-atom abstraction from phenol and the electron transfer from 1,2,4,5-tetramethoxybenzene to photoexcited 2,3-dibromo-1,4-naphthoquinone (DBNQ) and 2,3-dichloro-1,4-naphthoquinone (DCNQ) in the polar media originated from their triplet states. Nanosecond laser photolysis at 355 nm was carried out to determine the absorption spectra and coefficients of the corresponding triplet states, semiquinone, and anion radicals for a quantitative investigation of the mechanisms involved in the H-atom abstraction and the electron transfer. The steric hindrance of the substituted groups was indifferent to H-atom abstraction. The electronic structures of triplet DBNQ and DCNQ at 295 K were both revealed to be the mixed states of ³(n,π^*) with a ³(π,π^*) character.     

Dual-Wavelength Spectrophotometry

At present, dual-wavelength spectrophotometry is probably the least well known of the techniques of absorption spectrophotometry. However, recent improvements in application techniques have shown that for various organic and inorganic materials dual-wavelength spectrophotometry can provide higher sensitivity and selectivity than conventional spectrophotometry. This article reviews the principles and scope of dual-wavelength spectrophotometry, including derivative absorption spectrophotometry, in the hope that these techniques may be adopted more frequently in the future for resolving many analytical problems.