Cl2 Gas Research Articles

Tri‐halide vapor phase epitaxy of GaN using GaCl3 gas as a group III precursor

AbstractTri‐halide vapor phase epitaxy (THVPE) of GaN using GaCl3 gas generated by the reaction between metallic Ga and Cl2 gas at the source zone was investigated. From thermodynamic analysis, it was predicted that the driving force for GaN growth by THVPE would be larger than that by conventional mono halide vapor phase epitaxy (HVPE) using GaCl as a group III precursor. From the growth experiments, it was shown that the growth rate of GaN by THVPE was much higher than that by conventional HVPE under the same input partial pressure conditions. It was also revealed that GaN growth is possible at higher temperatures by THVPE. In photoluminescence (PL) and X‐ray diffraction (XRD) measurements, a GaN layer grown by THVPE at 1150 °C has optical properties and crystalline quality superior to that of a GaN layer grown by HVPE at 970 °C (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Quantification of Nitryl Chloride at Part Per Trillion Mixing Ratios by Thermal Dissociation Cavity Ring-Down Spectroscopy

Nitryl chloride (ClNO(2)) is an important nocturnal nitrogen oxide reservoir species in the troposphere. Here, we report a novel method, thermal dissociation cavity ring-down spectroscopy (TD-CRDS), to quantify ClNO(2) mixing ratios with tens of parts-per-trillion by volume (pptv) sensitivity. The mixing ratios of ClNO(2) are determined by blue diode laser CRDS of NO(2), produced from quantitative thermal dissociation of ClNO(2) in an inlet heated to 450 °C, relative to NO(2) observed in an unheated reference channel. ClNO(2) was generated by passing Cl(2) gas over a slurry containing a 1:10 mixture of NaNO(2) and NaCl. The TD-CRDS response was evaluated using parallel measurements of ClNO(2) by chemical ionization mass spectrometry (CIMS) using I(-) as the reagent ion and NO(y) (= NO + NO(2) + HNO(3) + ΣRO(2)NO(2) + ΣRONO(2) + HONO + 2N(2)O(5) + ClNO(2) + ...) chemiluminescence (CL). The linear dynamic range extends from the detection limit of 20 pptv (1 σ, 1 min) to 30 parts-per-billion by volume (ppbv), the highest mixing ratio tested. The ClNO(2) TD profile overlaps with those of alkyl nitrates, which has implications for nocturnal measurements of total alkyl nitrate (ΣAN = ΣRONO(2)) abundances by thermal dissociation (with detection as NO(2)) in ambient air.

Comb-drive GaN micro-mirror on a GaN-on-silicon platform

We report here a double-sided process for the fabrication of a comb-drive GaN micro-mirror on a GaN-on-silicon platform. A silicon substrate is first patterned from the backside and removed by deep reactive ion etching, resulting in totally suspended GaN slabs. GaN microstructures including the torsion bars, movable combs and mirror plate are then defined on a freestanding GaN slab by the backside alignment technique and generated by fast atom beam etching with Cl2 gas. Although the fabricated comb-drive GaN micro-mirrors are deflected by the residual stress in GaN thin films, they can operate on a high resistivity silicon substrate without introducing any additional isolation layer. The optical rotation angles are experimentally characterized in the rotation experiments. This work opens the possibility of producing GaN optical micro-electro-mechanical-system (MEMS) devices on a GaN-on-silicon platform.

High verticality InP/InGaAsP etching in Cl2/H2/Ar inductively coupled plasma for photonic integrated circuits

High verticality and reduced sidewall deterioration of InP/InGaAsP in Cl2/H2/Ar inductively coupled plasma etching is demonstrated for a hydrogen dominant gas mixture. Selectivity >20:1, an etch rate of 24 nm/s, and a sidewall slope angle of >89° have been measured for etch depths >7 μm. The Ar flow is minimized to reduce surface etch damage while increased Cl2 and H2 gas flow is shown to increase etch rate and selectivity. The high chamber pressure required for plasma ignition causes isotropic etching at the start and creates an undercut beneath the masking layer. A novel ignition scheme using a hydrogen gas “flood” is suggested and results are presented.

AEOL10150: A novel therapeutic for rescue treatment after toxic gas lung injury

New therapeutics designed as rescue treatments after toxic gas injury such as from chlorine (Cl2) are an emerging area of interest. We tested the effects of the metalloporphyrin catalytic antioxidant AEOL10150, a compound that scavenges peroxynitrite, inhibits lipid peroxidation, and has SOD and catalase-like activities, on Cl2-induced airway injury. Balb/C mice received 100ppm Cl2 gas for 5min. Four groups were studied: Cl2 only, Cl2 followed by AEOL10150 1 and 9h after exposure, AEOL10150 only, and control. Twenty-four hours after Cl2 gas exposure airway responsiveness to aerosolized methacholine (6.25–50mg/ml) was measured using a small-animal ventilator. Bronchoalveolar lavage (BAL) was performed to assess airway inflammation and protein. Whole lung tissue was assayed for 4-hydroxynonenal. In separate groups, lungs were collected at 72h after Cl2 injury to evaluate epithelial cell proliferation. Mice exposed to Cl2 showed a significantly higher airway resistance compared to control, Cl2/AEOL10150, or AEOL10150-only treated animals in response to methacholine challenge. Eosinophils, neutrophils, and macrophages were elevated in BAL of Cl2-exposed mice. AEOL10150 attenuated the increases in neutrophils and macrophages. AEOL10150 prevented Cl2-induced increase in BAL fluid protein. Chlorine induced an increase in the number of proliferating airway epithelial cells, an effect AEOL10150 attenuated. 4-Hydroxynonenal levels in the lung were increased after Cl2 and this effect was prevented with AEOL10150. AEOL10150 is an effective rescue treatment for Cl2-induced airway hyperresponsiveness, airway inflammation, injury-induced airway epithelial cell regeneration, and oxidative stress.

Thermodynamic analysis on HVPE growth of InGaN ternary alloy

Growth of InGaN alloy using hydride vapor phase epitaxy (HVPE) was investigated. Thermodynamic analysis was performed, taking account of the source zones. It was found that InCl3 and GaCl3, which are known to be essential for appreciable InGaN growth by HVPE, could be generated preferentially at the source zone by using a group-III metal and Cl2 gas. The analysis for the growth zone revealed that a significantly large driving force for both InN and GaN deposition is possible. The calculated vapor–solid distribution was close to a linear relationship by using a high V/III ratio, inert carrier gas, and high temperature. These facts suggest that an InGaN thick layer can be grown with a high growth rate and enough controllability of solid composition by employing InCl3 and GaCl3 precursors.

Direct Solid-State Electrochemical Synthesis of Silicon Tetrachloride from Silica at Ambient Temperatures and Pressures

Silicon tetrachloride (SiCl4) is one of the most important chemical compounds in the microelectronic industries. Commercial scale synthesis of SiCl4 is usually performed by roasting silica (SiO2) and cokes (C) under flowing chlorine (Cl2) gas at temperatures {greater than or equal to}900oC. At room temperatures and atmospheric pressures, the formation of SiCl4 from Cl2, SiO2 and C can be calculated to be favorable with ΔGreaction as low as -120.77 kJ/mol. This paper reports the use of I-V characterization technique in ambient conditions SiCl4 synthesis via direct solid state electrochemical synthesis reaction, starting with sodium chloride (NaCl), rice-husk derived-SiO2, and C (graphite/charcoal mixture).

Dimethylthiourea protects against chlorine induced changes in airway function in a murine model of irritant induced asthma

BackgroundExposure to chlorine (Cl2) causes airway injury, characterized by oxidative damage, an influx of inflammatory cells and airway hyperresponsiveness. We hypothesized that Cl2-induced airway injury may be attenuated by antioxidant treatment, even after the initial injury.MethodsBalb/C mice were exposed to Cl2 gas (100 ppm) for 5 mins, an exposure that was established to alter airway function with minimal histological disruption of the epithelium. Twenty-four hours after exposure to Cl2, airway responsiveness to aerosolized methacholine (MCh) was measured. Bronchoalveolar lavage (BAL) was performed to determine inflammatory cell profiles, total protein, and glutathione levels. Dimethylthiourea (DMTU;100 mg/kg) was administered one hour before or one hour following Cl2 exposure.ResultsMice exposed to Cl2 had airway hyperresponsiveness to MCh compared to control animals pre-treated and post-treated with DMTU. Total cell counts in BAL fluid were elevated by Cl2 exposure and were not affected by DMTU treatment. However, DMTU-treated mice had lower protein levels in the BAL than the Cl2-only treated animals. 4-Hydroxynonenal analysis showed that DMTU given pre- or post-Cl2 prevented lipid peroxidation in the lung. Following Cl2 exposure glutathione (GSH) was elevated immediately following exposure both in BAL cells and in fluid and this change was prevented by DMTU. GSSG was depleted in Cl2 exposed mice at later time points. However, the GSH/GSSG ratio remained high in chlorine exposed mice, an effect attenuated by DMTU.ConclusionOur data show that the anti-oxidant DMTU is effective in attenuating Cl2 induced increase in airway responsiveness, inflammation and biomarkers of oxidative stress.

The Effect of Fission Product Elements on the Behavior of Uranyl Species in Alkali Chloride Melts: a Contribution towards Reprocessing Spent Oxide Fuels

The reactions of uranyl(VI) containing chloride melts with molybdenum, niobium, zirconium and palladium were studied using high temperature electronic absorption spectroscopy. Depending on the nature of the added element uranium is reduced to uranyl(V) and uranium(IV) chloro-species and UO2. Palladium, niobium and zirconium can all be removed from a uranyl(VI)-containing melt using molybdenum metal and the melt can then be purified from Mo(III) ions by bubbling Cl2 gas. Such approach can be employed for removal a number of fission product elements from molten chloride baths during reprocessing spent oxide fuels.

ChemInform Abstract: Good Selectivity Between a NiCr Mask and GaAs and AlGaAs by Chemically Assisted Ion Beam Etching with Cl2 Gas.

The authors report highly selective etching rates between a Ni-Cr mask and GaAs and AlGaAs layers as well as highly anisotropic profiles in these materials at a nanometer scale using the Ni-Cr mask and chemical assisted ion beam etching. The etching rates of Ni-Cr, GaAs, and AlGaAs depend on Cl2 gas flux. ion beam energy, and ion beam current density. Selectivities of the order of 40:1 and 8:1 between GaAs, respectively. Al0.29Ga0.71As and Ni0.7Cr0.3, were obtained at an ion beam energy of 500 eV, beam current density of 0.2 mA/cm2, and a Cl2 flow of 4.2 ml/min

Effect of Gas Mixing Ratio on Etch Behavior of Y2O3 Thin Films in Cl2/Ar and BCl3/Ar Inductively Coupled Plasmas

This paper reports the results of a model-based analysis of the etch mechanism for the Y2O3 thin films in the Cl2/Ar and BCl3/Ar inductively coupled plasma. It was found that the BCl3/Ar plasma provides higher etch rate (except the case of pure BCl3 and Cl2 gases) as well as shows the non-monotonic dependence of the etch rate on the Ar mixing ratio. Plasma diagnostics by Langmuir probes indicated the noticeable influence of Ar mixing ratio on electron temperature and total density of positive ions. Using the model-based analysis of plasma chemistry and etch kinetics, it was demonstrated that the behavior of the Y2O3 etch rate in both gas mixtures generally corresponds to the neutral-flux-limited etch regime of the ion-assisted chemical reaction while the obtained differences cannot be explained assuming the Cl atoms to be the main chemically active species. Probably, in the BCl3-bases plasmas, the etch kinetics is significantly influenced by the BClx radicals.

Chlorine gas sensors using hybrid organic semiconductors of PANI/ZnPcCl16

PANI/ZnPcCl16 (polyaniline doped with sulfosalicylic acid/hexadecachloro zinc phthalocyanine) powders were vacuum co-deposited onto Si substrates, where Pt interdigitated electrodes were made by micromachining. The PANI/ZnPcCl16 films were characterized and analyzed by SEM, and the influencing factors on its intrinsic performance were analyzed and sensitivities of the sensors were investigated by exposure to chlorine (Cl2) gas. The results showed that powders prepared with a stoichiometric ratio of (ZnPcCl16)0.6(PANI)0.4 had a preferential sensitivity to Cl2 gas, superior to those prepared otherwise; the optimal vacuum co-deposition conditions for the films are a substrate temperature of 160 °C, an evaporation temperature of 425 °C and a film thickness of 75 nm; elevating the operation temperature (above 100 °C) or increasing the gas concentration (over 100 ppm) would improve the response characteristics, but there should be upper levels for each. Finally, the gas sensing mechanism of PANI/ZnPcCl16 films was also discussed.

Adsorption of Chlorine Dioxide Gas on Activated Carbons

Research and field experience with chlorine dioxide (ClO2) gas to decontaminate structures contaminated with Bacillus anthracis spores and other microorganisms have demonstrated the effectiveness of this sterilant technology. However, because of its hazardous properties, the unreacted ClO2 gas must be contained and captured during fumigation events. Although activated carbon has been used during some decontamination events to capture the ClO2 gas, no data are available to quantify the performance of the activated carbon in terms of adsorption capacity and other sorbent property operational features. Laboratory experiments were conducted to determine and compare the ClO2 adsorption capacities of five different types of activated carbon as a function of the challenge ClO2 concentration. Tests were also conducted to investigate other sorbent properties, including screening tests to determine gaseous species desorbed from the saturated sorbent upon warming (to provide an indication of how immobile the ClO2 gas and related compounds are once captured on the sorbent). In the adsorption tests, ClO2 gas was measured continuously using a photometric-based instrument, and these measurements were verified with a noncontinuous method utilizing wet chemistry analysis. The results show that the simple activated carbons (not impregnated or containing other activated sorbent materials) were the most effective, with maximum adsorption capacities of approximately 110 mg/g. In the desorption tests, there was minimal release of ClO2 from all sorbents tested, but desorption levels of chlorine (Cl2) gas (detected as chloride) varied, with a maximum release of nearly 15% of the mass of ClO2 adsorbed.

The Intercalation of Copper into Active Carbon and Its Application as a Catalyst for n-Amylalcohol Dehydration

The intercalation of CuCl2 salts into active carbon and its activity as catalyst on dehydration of n-amylalcohol has been investigated. In this research, the intercalation was conducted by reacting CuCl2 powder with active carbon and Cl2 gas at 3 atm, temperature 575 °C, at various heating time. This process was then followed by the reduction in the flowing hydrogen gas. Characterization of intercalation product was conducted by gas sorption method to determine surface area, pore radius, and pore volume distribution, and atomic adsorption spectroscopy (AAS) was used to determine the content of Cu metal. The test of catalytic activity on dehydration reaction of n-amylalcohol, was carried out in a flow reactor system at various temperatures. The results showed that the surface area and total pore volume increase with the longer time of intercalation process, and followed by increasing Cu content on active carbon. It was showed further that catalyst with highest Cu content, and the largest of both of surface area and total pore volume gives the best performance.

Effect of simultaneous source and bias pulsing in inductively coupled plasma etching

Pulsed rf plasmas show promise to overcome challenges for plasma etching at future technological nodes. In pulsed plasmas, it is important to characterize the transient phenomena to optimize plasma processing of materials. In particular, it is important to evaluate the effect of the ion energy and angular distribution (IEAD) functions during pulsing on etching of nanoscale features. In this work, the impact of simultaneous pulsing of both source and bias in an inductively coupled plasma on plasma characteristics and feature profile evolution is discussed using results from a two-dimensional reactor scale plasma model coupled to a Monte Carlo based feature profile model. Results are discussed for an Ar∕Cl2 gas mixture which is typically used for poly-Si etching. The consequences of duty cycle, pulse shape, and the phase lag between source and bias power pulses on discharge characteristics, IEADs to the wafer, and feature profile evolution are discussed. The low plasma density during the initial period of the pulse was found to introduce a high energy tail component to the IEADs. This high energy tail component can be affected by modifying the pulse shape. The Si etching rate is found to increase with increasing duty cycle but is lower compared to continuous mode of operation due to lower time averaged power deposition. Pulsing the source and bias out of phase provides for increased ion energies and fluxes to the wafer for a given duty cycle.

Protective oxide layers formed during electrochemical oxidation of hafnium carbide

The composition of oxide nanofilm formed on the HfC anode under electrolysis of a 3% NaCl solution at potentials between – 0.20 and +1.90 V is studied using the potentiodynamic method of polarization curves and Auger electron spectroscopy and SEM methods. The film consists of the upper layer formed in polymolecular chemosorption of O2 and Cl2 gases followed by the HfO2 + C (1 : 1) layer. Two inner layers represent a 7 at.% O2 solid solution in HfC and a mixture of HfC0.7O0.3 and HfO (7 : 1). The oxide film 30–40 nm thick formed at potentials up to 1.35 V is protective and ensures very high corrosion resistance of HfC without any further polarization.

Calciothermic Reduction of TiCl4 Gas during the Electrolysis of CaCl2 Melt

The calciothermic reduction of TiCl4 gas was studied firstly by using Ca-CaCl2 melt, to whose surface the gas was blown. The fine Ti particles settled down in the crucible, when the concentration of dissolved Ca was > 2 mol% at 1173 K. When < 2mol%Ca, a part of TiCl4 gas was dissolved probably as TiCl3 or TiCl2 into the CaCl2 melt, and it precipitated as the lower Ti oxides. When TiCl4 gas was blown to the molten CaCl2, which was electrochemically decomposed into Cl2 gas at the carbon anode and Ca at the Ti cathode, TiCl4 gas was reduced to the dendritic Ti on the cathode surface. Because the electrolyzed Ca reacted preferentially with the oxide crucibles, most of the oxygen ions combined with Ti2+ and Ti3+ and they formed TiO and Ti2O3.

Chemical Reaction on the Surface of As-Doped ZnO Thin Films during the Dry Etching Process

The etching properties of ZnO thin lms in an inductively coupled Cl2/BCl3/Ar plasma (ICP) were studied in terms of the etch rate and the selectivity as functions of the gas mixing ratio, the ICP coil power and the dc bias voltage. A maximum etch rate of 425 nm/min was obtained for a mixture of 10 % Cl2 gas addition to BCl3(80 %)/ Ar(20 %) plasma. The X-ray photoelectron spectroscopy (XPS) analyses of the ZnO surfaces etched at various Cl2/(Cl2+BCl3+Ar) mixing ratios revealed the formation of ZnClx and ClOx reaction by-products as a result of the increased etch rate with increasing Cl2 addition, compared with 20 % Ar/80 % BCl3 plasma etching. From the analysis of these data, we propose that the maximum etch rate may be explained by the concurrence of chemical and physical pathways in the ionassisted chemical reaction.

Sensitive properties of In-based compound semiconductor oxide to Cl2 gas

Aiming at detecting Cl2 gas, this study was made on how to make In-based compound semiconductor oxide gas sensor. The micro-property and sensitivity of In-based gas sensing material were analyzed and its gas sensitive mechanism was also discussed. Adopting constant temperature chemical coprecipitation, the compound oxides such as In–Nb, In–Cd and In–Mg were synthesized, respectively. The products were sintered at 600 °C and characterized by the Scanning Electron Microscope (SEM), showing the grain size almost about 50–60 nm. The test results show that the sensitivities of In–Nb, In–Cd and In–Mg materials under the concentration of 50 × 10−6 in Cl2 gas are above 100 times, 4 times and 10 times, respectively. The response time of In–Nb, In–Cd and In–Mg materials is about 30, 60 and 30 s, and the recovery time less than 2, 10 and 2 min, respectively. Among them, the In–Nb material was found to have a relatively high conductivity and ideal sensitivity to Cl2 gas, which showed rather good selectivity and stability, and could detect the minimum concentration of 0.5 × 10−6 with the sensitivity of 2.2, and the upper limit concentration of 500 × 10−6. The power loss of the device is around 220 mW under the heating voltage of 3 V.

Synthesis of organic semiconductor hexadecachloro zinc phthalocyanine and its gas sensitivity

Due to the difficulty in synthesizing perhalogenated metallophthalocyanine, the method of ammonium molybdate solid phase catalysis was introduced, and by using tetrachlorophthalic anhydride and urea as the raw materials, hexadecachloro zinc phthalocyanine (ZnPcCl16) was synthesized. Components of the composite were analyzed by energy spectrum, and its functional group structures and absorption peaks were characterized by IR and UV-vis spectroscopy. The thin films of gas sensors were prepared in a vacuum evaporation system and evaporated onto SiO2 substrates, where sensing electrodes were made by MEMS micromachining. The optimal conditions for the films are: substrate temperature of 150 °C evaporation current of 95 A and film thickness of 50 nm. The result showed that the sensors were ideally sensitive to Cl2 gas and could detect the minimum concentration of 0.3 ppm.