Detection of nitrogen metastable molecules by using the threshold ionization mass spectrometry

The N₂(A³Σu⁺) state has a rather long radiation lifetime, and its electron energy is high. Accordingly, it is expected that chemical reactions in the space where many metastable molecules are accumulated will be accelerated. Therefore, it is important to detect metastable molecules and to evaluate the number density of the molecules. With a view to detecting the N₂(A³Σu⁺) state in nitrogen plasma, the authors used threshold ionization mass spectrometry. For that purpose a quadrupole mass spectrometer (QMS) was modified to control its electron energy for ionization. Magnitude of the QMS signal was compared with the ionization cross section of the N₂(A³Σu⁺) state brought about by electron collision, and its number density was estimated. Using the method, it was recognized that the density of N₂(A³Σu⁺) increased in proportion to the discharge current. It was likewise recognized that the density of the current was rapidly decreased in the vicinity of the glass wall. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 147(1): 17–24, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10270     

Ionization current in N2 gas: XI. three‐dimensional analysis for loss processes of metastable particles affected by the reflection at the boundary

Loss of the metastable nitrogen molecule N₂(A³Σ⁺_u) in plane parallel electrodes has been investigated by us previously by solving the diffusion equation. Our procedure is based on an analysis using the third kind of boundary condition, which can take account of finite values for the density of N₂(A³Σ⁺_u) at the electrode surfaces. The values of the effective lifetime of N₂(A³Σ⁺_u) calculated from this analysis were reasonably consistent with our experiments. This paper describes the behavior of the effective lifetimes of RN₂(A³Σ⁺_u) in a cylindrical cavity. The analytical treatment of the diffusion equation for N₂(A³Σ⁺_u) proposed by us is extended to three‐dimensional space. We systematically report the effective lifetimes of metastable molecules in a cylindrical cavity. © 2000 Scripta Technica, Electr Eng Jpn, 130(4): 1–8, 2000     

Approximate calculation of triboelectric charge density (σ) of nanoscale contact electrification

We have analytically approximated the triboelectric charge densities generated by triboelectrification reaching equilibrium over time in contact-mode TENG. It is assumed that the surface density of states (SDOS), N_s(E) is constant. The amount of electron transfer at the interface is estimated by calculating the change in vacuum energy level due to the charge density induced in the upper metal electrode and the lower metal electrode within the nanoscale separation range. Numerical results show that N_s(E) and work function difference are dominant compared to dielectric constant (material property) and dielectric thickness (structure parameter).     

Microstructure and magnetic properties of aerosol‐deposited Sm‐Fe‐N thick films

In this study, the relationship among magnetic properties, Aerosol Deposition (AD) conditions, and microstructures in Sm‐Fe‐N AD films was investigated. The maximum thickness of 145µm was obtained under AD conditions of gas flow rate (gfr)=6liters/min for 10 min. The density of Sm‐Fe‐N films was in the range of 5.43 to 6.24g/cm³, that is, 71 to 81% of the X‐ray density of the Sm₂Fe₁₇N₃ compound reported (7.67g/cm³). The Sm‐Fe‐N AD films showed remanence in the range of 0.38 to 0.42 T, that is, 61 to 68% of that of the Sm‐Fe‐N host powder (0.62 T). The coercivities increased from 1.16 to between 1.74 and 1.79 T after the deposition because the grain size decreased from 1.94µm to 0.32µm. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(1): 8–13, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20214     

Refractive index properties of SiN thin films and fabrication of SiN optical waveguide

SiN thin films having excellent surface morphology for the optical device application were synthesized using a plasma enhanced chemical vapor deposition (PECVD) method at low temperature (350^°C) using silane (SiH₄) and nitrogen (N₂). The effects of the SiH₄/N₂ flow ratio, rf power and annealing on the SiN films were investigated. The optical and structural properties of SiN films were characterized using an ellipsometry, a fourier-transform infrared spectroscopy (FT-IR), and an atomic force microscope (AFM). The refractive index increased from 1.6 to 2.3 as the SiH₄/N₂ ratio was increased from 0.17 to 1.67. The rms surface roughness decreased from 14.1 to 3.6Å after post-deposition annealing process performed at 800^°C for 1hr in an air ambient. We could fabricate straight waveguides based on a three layer structure and have no problems with step coverage.     

Growth and characterization of device quality ZnO on Si(111) and c-sapphire using a conventional rf magnetron sputtering

In this article, it is shown that high quality ZnO films were grown on Si(111) and Al₂O₃(0001) substrates using a conventional rf magnetron sputtering. High-resolution X-ray diffractometry (HR-XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and photoluminescence (PL) investigations clearly confirmed that the ZnO films grown on Al₂O₃ (0001) at substrate temperatures above 650^∘C are single crystal as well as high optical quality. It is also estimated in both cases grown on Si and Al₂O₃ that an introduction of template pre-grown at 500^∘C can induce a homogeneous interface and improvement of emission characteristic by relaxing the strain caused by large lattice and thermal mismatch between the film and substrate and by reducing defect density in interface region.     

Electrical properties of ultrathin HfO2 gate dielectrics on partially strain compensated SiGeC/Si heterostructures

Ultrathin HfO₂ gate dielectrics have been deposited on strained Si_0.69Ge_0.3C_0.01 layers by rf magnetron sputtering. The polycrystalline HfO₂ film with a physical thickness of ∼6.5 nm and an amorphous interfacial layer with a physical thickness of ∼2.5 nm have been observed by high resolution transmission electron microscopy (HRTEM). The electrical properties have been studied using metal-oxide-semiconductor (MOS) structures. The fabricated MOS capacitors on Si_0.69 Ge_0.3C_0.01 show an equivalent oxide thickness (EOT) of 2.9 nm, with a low leakage current density of ∼4.5 × 10 ^{− 7} A/cm² at a gate voltage of –1.0 V. The fixed oxide charge and interface state densities are calculated to be 1.9 × 10¹² cm^{− 2} and 3.3 × 10 ¹¹ cm^{− 2}eV⁻¹, respectively. The temperature dependent gate leakage characteristics has been studied to establish the current transport mechanism in high-k HfO₂ gate dielectric to be Poole–Frenkel one. An improvement in electrical properties of HfO₂ gate dielectrics has been observed after post deposition annealing in O₂ and N₂ environments.     

Dielectric,ferroelectric, and piezoelectric properties of lead-free Ba0.95Ca0.05Ti1-xZrxO3 ceramics

Abstract

Ba_0.95Ca_0.05Ti_1-xZr_xO₃ (BCTZO) ceramics were prepared by a solid state reaction method. The samples were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and X-ray absorption near edge structure (XANES). The ceramics exhibit a pure perovskite structure. The average grain size gradually decreases with increasing Zr concentration. XANES results indicate that the intensities of pre-edge peaks dropped with increasing Zr concentration. The BCTZO ceramic of x?=?0.05 has the optimum electrical properties with the maximum dielectric constant (ε'_m), remanent polarization (2P_r), coercive electric field (2E_c) and piezoelectric charge constant (d₃₃) of 7,244, 12.54 (μC/cm²), 5.29 (kV/cm) and 288 (pC/N), respectively.     

Optical and sensor properties of ZnO nanostructure grown by thermal oxidation in dry or wet nitrogen

Zn films on glass were oxidized at 390°C in dry or wet N₂. As-prepared ZnO oxides were characterized by a scanning electron microscope (SEM), an X-ray diffractometer (XRD), a transmission electron microscope (TEN) and photoluminescence (PL) measurements. Gold electrodes were deposited on ZnO films to obtain ZnO gas sensors, which were characterized by exposure to ethanol at room temperature. The results show that the specimen oxidized in dry N₂ exhibits a sharp PL peak at 380 nm whereas that oxidized in wet N₂ exhibits a broad peak at 490 nm. The sensors demonstrate significant sensitivity to ethanol vapor at room temperature with a detection limit of 200 ppm for the sensor with ZnO oxidized in wet N₂. Recovery for the sensor with ZnO oxidized in wet N₂ can be achieved by illumination with natural light. However, for the sensor with ZnO oxidized in dry N₂, ultraviolet (UV) radiation is needed for recovery.     

Qualitative identification of nitrate nitrogen in compound fertilizers by infrared spectroscopy

ABSTRACT

In this study, NPK compound fertilizers containing nitrate nitrogen were tested by Fourier transform infrared spectroscopy (FTIR), and the relative contents of nitrate nitrogen and qualitative comparison were qualitatively identified. The raw materials of compound fertilizers: agricultural ammonium nitrate (AN), potassium nitrate (KNO₃) and ammonium phosphate (NH₄)₂HPO₄ were analyzed by infrared spectroscopy respectively. The results showed that the absorption peaks of nitrate (NO₃^?1) in solid agricultural fertilizers were 1384 cm^?1, 825 cm^?1. Furthermore, the NPK compound fertilizer with 4%, 5.5%, 6% and 9.5% nitrate nitrogen content were respectively tested by infrared spectroscopy. The results showed that with the increase of nitrate nitrogen content in the compound fertilizers, the relative intensity of the infrared absorption peaks of nitrate increased as well. Moreover, the relative intensity of the absorption peaks at 1384 cm^?1 and 825 cm^?1 are proportional to the content of nitrate in the nitro-compound fertilizer-containing ammonium nitrogen and nitrate nitrogen.     

The effects of forming gas anneal on the electrical characteristics of ir-electroded BST thin film capacitors

Abstract

The effect of various temperature nitrogen anneals prior to top electrode deposition on the ability of Ba_0.7Sr_0.3TiO₃ (BST) thin-film capacitors with both Ir and Pt top electrodes to withstand hydrogen damage was investigated. Experimental results show that samples that underwent a 750 °C N₂ pre-top electrode anneal exhibited the lowest leakage current density at positive bias for both Ir- and Pt-electroded devices after forming gas anneal. It was also found that DRAM polarization values decreased slightly after forming gas anneal. Also, a post-top electrode deposition 550°C O₂ anneal improved both electrical characteristics (lowered leakage and increased DRAM polarization) of these devices. Complete recovery of the leakage level prior to hydrogen damage was obtained after a 550°C N₂ recovery anneal for some devices independent of the pre-top electrode anneal. Ir- and Pt-electroded BST (40nm) capacitors have been shown to meet the 1 giga-bit DRAM leakage current requirement of 10^?8 A/cm² at 1.7 V. These Ir- and Pt-electroded BST devices achieved capacitance density levels of approximately 50 fF/μm².     

Study of DC circuit breaker of H2‐N2 gas mixture for high voltage

Global warming caused by such gases as CO₂ is a subject of great concern. Automobile emissions are an especially great problem in this respect. Therefore, hybrid cars are being widely developed and used. Because hybrid cars use electric power and gasoline, their emissions of CO₂ are reduced. The electric motor of a hybrid car is driven by a battery, which has large capacity. Therefore, relays must interrupt a high DC current on switching between the electric motor and the gasoline engine, and hydrogen gas‐filled relays are used for the purpose. In interruption tests in which we investigated the basic characteristics of hydrogen gas, the DC current did not reach a current‐zero point. Thus, the current must be coerced to zero by using a high arc voltage. The loss coefficient and arc voltages of hydrogen are high, and we therefore performed interruption tests using a high arc voltage. Interruption tests and dielectric breakdowns test of air, pure hydrogen, and a hydrogen‐nitrogen mixture indicated that an 80%–20% H₂–N₂ mixture is the most effective. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(2): 9–17, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21042     

Effect of Ni addition on PNZT tungsten bronze structure

Lead niobate zirconate titanate (PNZT) with general formula 0.5PbNb₂O₆–0.5Pb(Zr_xTi_1-x)O₃ (where x?=?0.15, 0.25, 0.35) and lead nickel niobate zirconate titanate (PNNZT) with general formula Pb(Ni_xNb_0.5-xZr_0.25Ti_0.25)O₃ (where x?=?0.167, 0.250, 0.333) have been prepared by conventional solid state reaction. The phase formation has been studied by X – ray diffraction analysis. Raman investigations have been carried out in the 200–1000 cm^?1 wave number range. The structural changes observed in the X – ray diffraction pattern has been further confirmed by Raman analysis. The major changes in the E(1TO), A₁(1TO) and E?+?B₁ phonon modes suggest the structural change from cubic to rhombohedral with increase in Ni concentration in PNNZT. The optical band gap has been calculated from UV – Vis absorption spectra.     

Normal-to-relaxor ferroelectric phase transition and electrical properties in Nb-modified 0.72BiFeO<Subscript>3</Subscript>-0.28BaTiO<Subscript>3</Subscript> ceramics

Preparation and electrical properties of sintered bodies consisting of monophase cubic spinel oxides, Cr_XMn_1.5Co_(1.0-X)Ni_0.5O₄ (0 ≦ X ≦ 0.42), were investigated. Specimens with compositions within X = 0.42 were prepared as starting materials. The element of Cr was used to exchange Co³⁺ in octahedral sites (B sites) with Cr³⁺ so that the hopping mechanism can be discussed. The sintered bodies with mono cubic spinel structure were confirmed to be prepared by heat-treatment for 48 h in air at 1000 °C to convert them into a cubic spinel structure after sintering at 1400 °C. The semiconductive characteristics of the sintered bodies were determined as p-type because the Seebeck coefficients were all positive. The electrical conduction of the sintered bodies was concluded to be controlled by the small polaron hopping mechanism. In the region 0.1 ≦ X ≦ 0.42, the lattice constant increases and electrical conduction (σ) decreases linearly with increasing Cr concentration. The decrease in σ and the increase in the lattice constant corresponded to the increase in Cr concentration by which the jumping distance of electrons between Mn³⁺ and Mn⁴⁺ is lengthened.     

Microstructural and piezoelectric properties of PZN substituted PMN-PZT ceramics for multilayer piezoelectric transformer

In this paper, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformers, Pb[(Mn_1/3,Nb_2/3)_0.07(Zn_1/3Nb_2/3)_a (Zr_0.48Ti_0.52)_1-0.07-aO₃] ceramics were prepared with the variations of PZN from 2 to 14 mol% and their dielectric and piezoelectric properties were investigated. Sintering temperature was varied from 940 to 1000^∘C. At 8 mol% PZN substituted specimen sintered at 970^∘C, electromechanical coupling factor(kp), mechanical quality factor(Qm), dielectric constant and peizoelectric constant(d₃₃) showed the optimal values of 0.536, 1803, 1551 and 328[pC/N], respectively, for multilayer piezoelectric transformer application.     

Chlorine Gas Sensing Properties of ZnO-CaO Ceramics

The chlorine gas sensing properties of pure ZnO (PZ) and CaO-added ZnO (CAZ) ceramics with relative densities of 48–65% were investigated from 25–380°C in Cl₂ concentration range from 0.9 ppm to 20 ppm using air or N₂ as a carrier gas. In the entire temperature range, the conductivity of PZ and CAZ ceramics decreased by introducing Cl₂ gas. 3 mol% CAZ showed a Cl₂ sensitivity ((0)/(Cl₂)) of 10 for 0.9 ppm Cl₂ in air at 300°C, suggesting its usefulness for sensing of a low-concentration Cl₂ gas below 1 ppm. The CaO addition was found to decrease the Cl₂ sensitivity but to improve the recovery process after removing Cl₂ gas. These effects are attributed to changes in the amount and stability of adsorbed oxygen and to subsequent changes in Cl₂ adsorption behavior.     

Characterization of hetero-epitaxial PZT capacitor

Abstract

A hetero-epitaxial Au/PbZr_0.48Ti_0.52O₃(PZT)/SrRuO₃(SRO) capacitor was fabricated on a single crystal SrTiO₃ (STO) substrate by pulsed laser deposition. An SRO buffer layer (a nucleation layer) was formed at the SRO/STO interface to ensure the highly epitaxial growth of the PZT and SRO films. An X-ray diffraction measurement revealed that the (00l) planes of the PZT and SRO grew parallel to the substrate surface. A transition layer of ～ 5 nm thickness was observed at the SRO/STO interface by high-resolution transmission electron microscopy (HR-TEM). This transition layer corresponds to the nucleation layer intentionally grown at the interface. Remanent polarization of the capacitor was 32.1 μC/cm² due to the good epitaxial growth of the films.     

Hydrothermal synthesis of LiFePO4 with small particle size and its electrochemical properties

Lithium iron phosphate (LiFePO₄) powders were prepared by hydrothermal reactions under a nitrogen atmosphere or an air atmosphere, and the microstructure and electrochemical properties of the LiFePO₄ powders were investigated. The LiFePO₄ powder prepared under the nitrogen atmosphere (LiFePO₄–N₂) had a small particle size in the range of 300–500 nm, whereas the powder prepared under the air atmosphere (LiFePO₄?air) had a large particle size in the range of 1–5 μm. Although the Fe²⁺/Fe³⁺ ratio was not significantly different in both LiFePO₄ powders, the Fe²⁺/Fe³⁺ ratio in the precursor suspension prepared under the nitrogen atmosphere was much higher than that prepared under the air atmosphere, thereby resulting in the small particle size of the LiFePO₄–N₂ powder. The discharge capacity of a LiFePO₄–N₂ electrode was 149 mAh g^?1 at a low current density of 10 mA g^?1, whereas that of a LiFePO₄?air electrode was 83 mAh g^?1. Impedance analyses indicated that the charge transfer resistances normalized to the surface area of LiFePO₄ particles for the LiFePO₄–N₂ and LiFePO₄?air electrodes were 4.6 and 4.8 Ω m², respectively. These values were not significantly different. This revealed that the factor dominating the electrochemical properties of LiFePO₄–N₂ and LiFePO₄?air powders was particle size and not crystalline lattice or Fe²⁺ concentration.     

The sintering behavior and microwave dielectric properties of Mg4(Nb,Sb)2O9 ceramics

The sintering behavior, microstructure and microwave dielectric properties of Mg₄(Nb_2?x Sb _x )O₉ (0?≤?x?≤?2) solid solutions were investigated systematically by X-ray diffraction(XRD), scanning electron microscopy(SEM) and a network analyzer. The solid solutions of Mg₄(Nb_2?x Sb _x )O₉ was formed with x value being no more than 1.6. The dielectric constant (?) of the sintered ceramics decreased from 13.06 to 6.28 with Sb content x from 0 to 1.6. With a substitution of Sb⁵⁺ for Nb⁵⁺ (0.04?≤?x?≤?0.08), the sintering temperature of Mg₄Nb₂O₉ ceramics was decreased from 1400 to 1300 °C without degradation of the Qf values. The optimum microwave dielectric properties of ??～?12.26, Qf?～?168,450 GHz, and τ _f?～??56.4 ppm/°C were obtained in the composition of Mg₄(Nb_1.6Sb_0.4)O₉ sintered at 1300 °C.     

Oxygen radical density measurement in O2–N2 gas mixture plasma by means of a thin platinum wire

The oxygen radical density was measured in a weakly ionized plasma in an O₂–N₂ gas mixture by using a simple platinum thin‐wire sensor. The increased temperatures of the platinum wire caused by the energy released in the recombination of two oxygen radicals on the platinum surface were measured by varying the nitrogen gas mixture ratio and were compared with the oxygen radical densities theoretically calculated under the same plasma conditions. The relation between the wire temperature and the oxygen radical densities was cross‐checked by quantitative measurement of oxygen radical densities with a quadrupole mass spectrometer. All of these results made it possible to determine the oxygen radical density experimentally from the platinum wire temperature alone. The influence of the ambient gas temperature on the radical density measurement is also discussed. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(4): 14–20, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20018