Showing papers on "Argon published in 1979"
TL;DR: In this paper, the chemical structures of thin SiO2 films, thin native oxides of GaAs (20-30 A), and the respective oxide-semiconductor interfaces, have been investigated using high-resolution X-ray photoelectron spectroscopy.
Abstract: The chemical structures of thin SiO2 films, thin native oxides of GaAs (20-30 A), and the respective oxide-semiconductor interfaces, have been investigated using high-resolution X-ray photoelectron spectroscopy. Depth profiles of these structures have been obtained using argon ion bombardment and wet chemical etching techniques. The chemical destruction induced by the ion profiling method is shown by direct comparison of these methods for identical samples. Fourier transform data-reduction methods based on linear prediction with maximum entropy constraints are used to analyze the discrete structure in oxides and substrates. This discrete structure is interpreted by means of a structure-induced charge-transfer model.
292 citations
TL;DR: In this paper, a statistical-mechanical model for physical adsorption of a gas on a solid substrate is developed, based on Van der Waals' concept of dividing the interaction potential between a pair of molecules into a hard-sphere repulsive part and an infinitely weak and long-range attractive part.
Abstract: A statistical-mechanical model for physical adsorption of a gas on a solid substrate is developed, based on Van der Waals' concept of dividing the interaction potential between a pair of molecules into a hard-sphere repulsive part and an infinitely weak and long-range attractive part. The interaction between the substrate and gas molecules is similarly modeled by a hard-wall repulsive potential with long-range attractive tail. For a specific choice of the intermolecular and wall-molecule attractive terms, an explicit solution is obtained for the model. This solution shows that three different classes of adsorption isotherm are possible: in class I, the adsorption is infinite in the limit that the gas pressure approaches the saturated vapor pressure, in class II the adsorption remains finite in the limit, while in class III the adsorption becomes negative in the limit. If the temperature of crossover between different classes is plotted as a function of $\frac{{\ensuremath{\epsilon}}_{w}}{\ensuremath{\alpha}}$, where ${\ensuremath{\epsilon}}_{w}$ and $\ensuremath{\alpha}$ are respectively the minimum of the wall-molecule potential and the integrated strength of intermolecular attractions, then the resulting curve has the same shape as the bulk phase coexistence curve. The model shows agreement with experimental results for the adsorption of argon, krypton, and xenon on graphite, and for argon adsorbed on xenon, as well as with recent computer-simulation results for argon adsorbed on carbon dioxide.
176 citations
TL;DR: In this article, the authors measured the charge-state spectra of recoil ions generated in single collisions of 25-45-MeV chlorine ions with targets of helium, neon, and argon.
Abstract: The author has measured charge-state ($q$) spectra of recoil ions generated in single collisions of 25-45-MeV chlorine ions with targets of helium, neon, and argon. A high-efficiency time-of-flight spectrometer was used to identify the charge-to-mass ratio of the slowly moving recoils. Recoil $q$ up to + 8 (neon) and + 11 (argon) were observed. Cross sections for recoil production were measured as a function of projectile energy and incident charge state. The energy dependence of the cross sections is quite weak, while the recoil-$q$ dependences show clear shell effects in argon. For the lower-$q$ recoils, the cross sections are reasonably well described by the model of Olson, which treats the target electrons as moving independently. For higher $q$, a model based on energy deposition by the projectile with the target electrons, followed by statistically weighted electron emission, gives a better description of the data.
162 citations
TL;DR: In this article, cross sections for electron-impact ionization of singly excited states of the rare gases (neon, argon, krypton, xenon), cadmium, and mercury) were calculated based upon the symmetric binary-encounter model, together with a semi-empirically determined momentum distribution function for the bound, excited electron.
Abstract: Cross sections have been calculated for electron-impact ionization of singly excited states of the rare gases (neon, argon, krypton, xenon), cadmium, and mercury. The calculations are based upon the symmetric binary-encounter model, together with a semiempirically determined momentum distribution function for the bound, excited electron. Good agreement is obtained with the available experimental data, as well as with existing theoretical results, in the low- to intermediate-energy range.
158 citations
TL;DR: A photoelectron spectrometer which permits the study of solids in the presence of gas at up to 1 Torr pressure has been developed and the main factors considered in its design and construction are described in this article.
139 citations
TL;DR: The mechanism of photon emission in the rare-gas proportional scintillation counter was ascribed to the radiative de-excitation of excited molecules, R 2 ∗ →R+R+hv, by determining emission spectra experimentally as mentioned in this paper.
128 citations
TL;DR: In this paper, an argon saturated aqueous alkali metal salt solutions is observed during insonation at 460 kHz and diffuse emission lines are observed at ∼554 nm and ∼740 nm for Na and K, respectively.
Abstract: Emission from argon saturated aqueous alkali metal salt solutions is observed during insonation at 460 kHz. It is postulated to arise from de‐excitation of excited alkali metal atoms formed by free radical reduction processes. In addition to the emission resonance lines, diffuse bands are observed at ∼554 nm and ∼740 nm for Na and K, respectively. The latter are due to emission from alkali metal–argon exciplexes and are known to occur when mixtures of alkali metal vapor and argon are rapidly compressed. An estimate of the cavitational temperatures and pressures is obtained by comparison of experimental emission band parameters with those derived theoretically.
112 citations
TL;DR: The use of a halocarbon/argon atmosphere in the sampling manifold of a graphite rod electrothermal vaporization device employed for the introduction of samples into a high-frequency, inductively coupled argon plasma source for optical emission spectroscopy is shown to permit sensitive determination of elements such as boron, molybdenum, zirconium, chromium, and tungsten which form refractory oxides or carbides as mentioned in this paper.
Abstract: The use of a halocarbon/argon atmosphere in the sampling manifold of a graphite rod electrothermal vaporization device employed for the introduction of samples into a high-frequency, inductively coupled argon plasma source for optical emission spectroscopy is shown to permit sensitive determination of elements such as boron, molybdenum, zirconium, chromium, and tungsten which form refractory oxides or carbides which limit attainable sensitivity when an argon atmosphere alone is employed. Typical improvements in the detection limits obtained with this technique are between one and two orders of magnitude, so that subnanogram amounts of these elements may be detected; linear dynamic concentration ranges of four orders of magnitude have been obtained with the procedure employed. 2 figures, 3 tables.
106 citations
TL;DR: In this paper, a laser-excited fluorescence method has been used to determine the rates at which CF2HCl molecules dissociate into CF2+HCl fragments during CO2 laser pulses of uniform fluence and known intensity.
Abstract: A laser‐excited fluorescence method has been used to determine the rates at which CF2HCl molecules dissociate into CF2+HCl fragments during CO2 laser pulses of uniform fluence and known intensity. A study has been made of the dependence of the rate on CO2 laser intensity and pressure of Ar buffer gas from the collision‐free regime to atmospheric pressure. The effect of increasing Ar pressure is initially to increase the CF2HCl dissociation rate; above a moderate pressure (∼50 Torr), the rate is independent of Ar pressure up to atmospheric pressure. The data has been compared to a model, which adequately reproduces all the experimental data. The model treats the effect of collision between CF2HCl and the argon buffer gas in terms of rotational equilibration or ’’hole filling’’ in the discrete energy level region of CF2HCl. The discrete energy levels are interfaced to a quasicontinuum of vibrational–rotational states in a self‐consistent manner which incorporates a background of nonpumpable CF2HCl states as a finite heat bath interacting with the pump mode. The model is used to calculate the rate of formation of product CF2 molecules as a function of argon pressure and CO2 laser intensity. The quasicontinuum for CF2HCl is predicted to begin about four quanta above the ground state. The absorption cross section in the quasicontinuum is shown to decrease from 10−18 to 10−20 cm2 at V=15. The energy distribution in CF2HCl is predicted to be decidedly nonthermal both below and beyond threshold.
104 citations
IBM1
TL;DR: In this paper, the authors studied the behavior of the stresses in Niobium films and found that the stress is determined mainly by the microstructure and the energetic particle bombardment.
102 citations
TL;DR: In this paper, electron microscopy has been used to study silicon and germanium particles prepared by evaporation in argon at low pressure and showed frequently distinct crystal habits.
TL;DR: In this article, the applicability of inductively coupled argon plasma (ICAP) as a detector in high-performance liquid chromatography (HPLC) was investigated, and the influence of the flow-rate and the nature of the mobile phase on the operation of the ICAP source, and on peak broadening, sensitivity, linearity and detection limits was determined.
TL;DR: In this article, a two-step technique was used to identify and characterize the CuInS2 thin films produced by sputtering pure copper and pure indium to H2S gas diluted with argon and showed a preferred orientation of the (112) plane parallel to the substrate.
Abstract: CuInS2 thin films have been made from copper, indium, and hydrogen sulfide gas using a two‐step technique which involves exposing Cu‐In films produced by sputtering pure copper and pure indium to H2S gas diluted with argon. X‐ray diffraction, Auger electron spectroscopy, optical transmission, and electrical measurements were used to identify and characterize the CuInS2. The resulting films were all p type with resistivity in the range 0.1–500 Ω cm and showed a preferred orientation of the (112) plane parallel to the substrate.
TL;DR: Using the quartz oscillator technique, the authors measured the sputtering yield of silicon bombarded with 10-140-keV argon and 10-540-kV xenon, respectively.
Abstract: Using the quartz oscillator technique, we have measured the sputtering yield of silicon bombarded with 10–140‐keV argon and 10–540‐keV xenon, respectively. Considerable effort has been devoted to achieving high‐purity silicon films with smooth surfaces and to calibrating the microbalance. In situ combination of the quartz oscillator technique with Rutherford backscattering allowed a quantitative determination of the fluence dependence of the sputtering yield. Measurements with xenon at 140 and 270 keV showed that the sputtering yield of silicon increases by about 25% due to loading of the target with projectile atoms. A simple estimate indicates that the yield enhancement is caused, to a large extent, by the increase in nuclear‐energy deposition resulting from the accumulation of the heavy projectiles in silicon. The measured steady‐state sputtering yields are in satisfactory agreement with results achieved by other experimental techniques. Discrepancies with results derived by other authors applying the ...
TL;DR: In this article, the authors used adsorption microcalorimetry at 77 K to show that a two-dimensional fluid → solid phase change at the completion of the argon or nitrogen monolayer.
TL;DR: The Pithon pulsed electron beam accelerator was used to implode an argon plasma at 4 TW as mentioned in this paper, and the conditions were inferred from hydrogen-like and helium-like x-ray emission spectra.
Abstract: The Pithon pulsed electron beam accelerator was used to implode an argon plasma at 4 TW. The plasma was prepared by microwave preionization of an annular column of gas injected between the output electrodes of the pulser. The electrodynamic behavior implied that most of the gas was involved in the pinch. The plasma conditions were inferred from hydrogenlike and heliumlike x‐ray emission spectra. Final pinch dimensions were determined from x‐ray pinhole photographs and laser shadowgraphs.
TL;DR: A comparison of the inventory of inert gases found in the atmospheres of Venus, Earth, and Mars suggests that these components are due to outgassing from the planetary interiors.
Abstract: The first gas chromatographic analysis of the lower atmosphere of Venus is reported. Three atmospheric samples were analyzed. The third of these samples showed carbon dioxide (96.4 percent), molecular nitrogen (3.41 percent), water vapor (0.135 percent), molecular oxygen [69.3 parts per million (ppm)], argon (18.6 ppm), neon (4.31 ppm), and sulfuir dioxide (186 ppm). The amounts of water vapor and sulfur dioxide detected are roughly compatible with the requirements of greenhouse models of the high surface temperature of Venus. The large positive gradient of sulfur dioxide, molecular oxygen, and water vapor from the clould tops to their bottoms, as implied by Earth-based observations and these resuilts, gives added support for the presence of major quantities of aqueous sulfuric acid in the clouds. A comparison of the inventory of inert gases found in the atmospheres of Venus, Earth, and Mars suggests that these components are due to outgassing from the planetary interiors.
TL;DR: In this paper, a miniature inductively coupled plasma source for atomic emission spectrometry is described and a preliminary evaluation of its analytical capabilities is presented, which is very economical to sustain and works well with less than 1 kW of RF power and 8L/min argon coolant gas.
Abstract: : A miniature inductively coupled plasma source for atomic emission spectrometry is described and a preliminary evaluation of its analytical capabilities is presented. The mini-ICP is very economical to sustain and works well with less than 1 kW of RF power and 8L/min of argon coolant gas. In addition, the new source possesses some unique operating characteristics which simplify sample introduction. In this paper, detection limits, multi-element capabilities, and other analytical features of the mini-ICP are compared with those demonstrated by a conventional ICP source and shown to be comparable. In addition, the two plasmas are shown to exhibit similar excitation temperatures in the respective analyte observation regions (i.e., plasma tail flames). These results suggest that the mini-ICP possesses the same desirable atomization and excitation characteristics as conventional ICP sources. (Author)
TL;DR: In this article, a high temperature source (2800 K) was developed to produce a free jet expansion of copper vapor (Tsource=2500 K, Psource∼100 Torr).
Abstract: A high temperature source (2800 K) has been developed to produce a free jet expansion of copper vapor (Tsource=2500 K, Psource∼100 Torr). The supersonic beam formed under these conditions was characterized through analysis of the laser induced excitation spectrum for the B 1Σu+←X 1Σg+ band system of Cu2. Excitation was accomplished with an argon ion pumped stilbene cw dye laser. The Cu2 formed in the expansion was characterized by a vibrational temperature, Tvib=950±100 K and a rotational temperature, Trot=800±50 K. A new band system attributed to diatomic or triatomic copper has been observed.
TL;DR: The results of a comprehensive study of the energy distributions of ions sputtered from 31 pure elements and two compounds by a 5.5 keV O+2 beam are presented in this article.
TL;DR: Amorphous SixC1−x as discussed by the authors alloys are prepared by simultaneous reactive sputtering of silicon and graphite in a H2•Ar gas mixture, and hydrogen contents are measured for the entire range of x by electron spectroscopy for chemical analysis (ESCA), Rutherford•backscattering method, and thermal evolution of hydrogen.
Abstract: Amorphous SixC1−x : H alloys are prepared by simultaneous rf reactive sputtering of silicon and graphite in a H2‐Ar gas mixture. Silicon, carbon, and hydrogen contents are measured for the entire range of x by electron spectroscopy for chemical analysis (ESCA), Rutherford‐backscattering method, and thermal evolution of hydrogen. Evolution temperature dependence of the number of evolved hydrogen atoms is measured. The hydrogen‐evolution behavior and the optical gap are x dependent. These phenomena are discussed in the light of chemical‐bonding states.
TL;DR: In this article, the authors discuss the approaches to reactive d.c. sputtering and a criterion for the conditions which allow both the sputtering of metal at the target and the oxidation of the growing film on the substrate.
TL;DR: In this paper, the influence of argon partial pressure pAr on the photoconductivity, four-probe conductivity and photoluminescence of rf−sputtered a−Si-H alloys was reported.
Abstract: We report the influence of argon partial pressure pAr on the photoconductivity, four‐probe conductivity and photoluminescence of rf‐sputtered a‐Si–H alloys. As pAr is increased from 5 to 30 mTorr, for fixed hydrogen partial pressure pH, photoconductivity increases by as much as three orders of magnitude and then saturates. Over this range the dark conductivity activation energy decreases, a plot of log conductivity versus inverse temperature becomes increasingly less linear and the photoluminescence intensity increases slightly and then drops back. We note that high pAr films become slowly contaminated upon exposure to air. These results are interpreted in terms of a reduction in energetic silicon atom bombardment of the growing film with increased pAr. For our sputtering arrangement, we show that silicon atoms ejected from the target become significantly more thermalized at pAr=10 mTorr than at 5 mTorr. Based primarily on the fact that the conductivity activation energy is more strongly dependent on pH f...
TL;DR: In this paper, the temporal and spectral behavior of absorption in the visible by e-beam excited argon, krypton, and xenon have been investigated with and without additives.
Abstract: The temporal and spectral behavior of absorption in the visible by e -beam excited argon, krypton, and xenon have been investigated with and without additives. The probe light used was from an argon-ion pumped, tunable dye laser, or from the visible lines of the argon-ion laser itself. Strong absorption was observed at all wavelengths investigated (450-620 nm). Structured absorptions out of atomic and molecular excited states have been identified by their temporal, spectral, and pressure behavior. The ubiquity of these absorptions, which is not fully understood, should have serious implications for the development of new visible lasers that operate during the electron-beam pumping pulse.
TL;DR: In this article, a three-body reaction with a rate constant of (1.0±0.3) × 10−32 cm 6 sec−1 was studied by monitoring the time dependence of the 987.6 nm absorption band due to Ar*2 under various conditions.
Abstract: Argon excited diatomic molecules Ar*2(3J+u)were produced by irradiating argon gas with short electron beam pulses. The kinetic behavior was studied by monitoring the time dependence of the 987.6 nm absorption band due to Ar*2 under various conditions.The method is largely different from the vacuum UV emission spectroscopy used previously in such kinetic studies. Ar*2 was found to be produced by a three‐body reaction with a rate constant of (1.0±0.3) ×10−32 cm 6 sec−1. Then, the rate constants and cross sections of energy transfer were determined for 12 fundamental acceptor molecules. The theoretical formula proposed previously for Penning ionization was applied to energy transfer between Ar*2 cross sections given by the formula have the values comparable to the observed ones.
TL;DR: In this paper, a field ion source was designed to operate at very low temperatures with a physisorbed surface supply to the ionization region, which was found to give beams of high angular current density and is expected to have low energy spread in the beam.
Abstract: We have built and carried out initial tests on a field ion source that has been designed to operate at very low temperatures with a physisorbed surface supply to the ionization region. This mode has been found to give beams of high angular current density and is expected to have low energy spread in the beam. Presently we have measured dI/dΩ?10 to 60/sr with a probable energy spread of ?l eV. The UHV system allows processing of the field emitter under clean, high vacuum conditions. A liquid He cooled finger maintains the tip at controlled temperatures from that of liquid He to room temperature. The tip is mounted on a sapphire block to provide both excellent thermal conduction and electrical insulation to ?30 kV. Differential pumping allows a high supply pressure of H2, He, Ar, etc. in the region of the tip (≳ 10−2 Torr) and a low pressure in the rest of the system. Observation on the characteristics of the field ionization pattern are made under varying conditions of pressure, temperature, field and tip ...
TL;DR: In this article, the L emission spectrum of argon has been recorded with very high resolution and 123 lines have been observed in the spectrum and their transition energies have been determined with high accuracy (≥ 5 meV).
Abstract: The L emission spectrum of argon has been recorded with very high resolution. 123 lines have been observed in the spectrum and their transition energies have been determined with high accuracy (≥ 5 meV). Auger transition rates are discussed in terms of observed widths of the corresponding X-ray transitions. Experimental Ar 2p3p state widths are obtained showing considerable disagreement with previously calculated values.
TL;DR: A comparison of an end-on viewed argon inductively coupled plasma (ICP) operated in the horizontal position with the conventional side-on-viewed argon ICP was carried out using the same experimental setup as discussed by the authors.
Abstract: A comparison of an "end-on" viewed argon inductively coupled plasma (ICP) operated in the horizontal position with the conventional "side-on" viewed argon ICP was carried out using the same experimental setup. The end-on ICP required an air cutoff stream located toward the tip of the luminous discharge, to protect the optics and to increase linearity ranges, and the orifice diameter of the central tube of the torch was widened to 1.9 mm, to improve line/background ratios. With the end-on viewed plasma the linearity ranges, the susceptibility to solute vaporization and to ionization matrix effects, and the detection limits in an organic solvent were insignificantly different from those observed with the side-on viewed plasma. Detection limits with aqueous samples were always significantly lower with the end-on viewed plasma, usually five- to tenfold lower, in a few instances, 20-fold lower. With the end-on viewed plasma the optimal observation region for both single and simultaneous multielement analysis is one and the same and is extremely easy to locate.
TL;DR: In this paper, the effects of an intermediate, isothermal annealing treatment in argon on the oxidation kinetics in dry oxygen of Cu 10%Ni and Cu 24%Ni at 800°C and Cu 80% Ni at 1000°C using a semi-automatic microbalance.