Addition Of Argon Research Articles

Cathodoluminescence properties of diamond films synthesized by microwave-plasma-assisted chemical vapour deposition

A variety of diamond films were synthesized in microwave plasmas of the CO-N 2-H 2, CO-B(OC 2H 5) 3-H 2, CO-H 2-Ar and CO-H 2 systems. The correlation between their crystallinities and cathodoluminescence (CL) properties led to the following conclusions. Non-doped films had twin peaks at 2.82 eV (440 nm) and near 2.3 eV (530–600 nm) which were categorized as band A luminescence. The intensity ratio I 2.8/ I 2.3 of these twin peaks was smaller than 1. This value became larger than 1 as a result of nitrogen doping. According to scanning electron microscopy observations and X-ray diffraction analyses, nitrogen was considered to be selectively incorporated into (111) sectors. Consideration of these experimental facts in conjunction with earlier findings led to the conclusion that (100) sectors emitted high energy (blue) band A luminescence ( I 2.8/ I 2.3 > 1) and (111) sectors were responsible for low energy (green) fluorescence ( I 2.8/ I 2.3 < 1). An intense green emission was observed for a boron-doped film, which had a peak at 2.34 eV (530 nm). This emission was classified as a lower energy peak (2.2 eV) of band A luminescence. Boron-doped films exhibited green emission (2.34 eV, 530 nm) of band A luminescence five times as intense as that of non-doped films, whereas nitrogen-doped films exhibited only a little increase in the intensity of the blue emission (2.8 eV, 440 nm) of band A luminescence. The intensity of the blue emission was presumed to increase by enhanced nitrogen incorporation into (100) sectors. A sharp peak corresponding to the GR 1 band was observed at 1.67 eV (741 nm) for the film synthesized in a CO-H 2-Ar system. This luminescence originated from the vacancies in the diamond film synthesized under severe bombardment of high energy electrons and ions in the argon-involving plasma. Argon addition to a CO-H 2 system suppressed the CL intensity of the synthesized diamond film which was characterized by a relatively intense red emission (GR1) at 1.67 eV (741 nm).

Enhancement of Photoresist Etch Rates by Argon Metastables in a Plasma Afterglow Reactor

AbstractThe etching of a novolak-based positive photoresist was studied downstream of O2/CF4 and Ar/O2/CF4 plasmas. Gas phase electron resonance was used to quantitatively track the two primary etchant species, atomic oxygen and atomic fluorine. These species were then correlated to etch rates as determined by laser interferometry. In addition to being industrially relevant, the downstream reactor allows the influence of neutral chemistry and surface activation to be deconvoluted from that of ion bombardment and strong electric fields, which traditionally make processes occurring in the body of the plasma so difficult to understand. The maximum in etch rate with respect to CF4 addition to an oxygen plasma yields an optimum ratio of O/F of 20 at 150 °C. The addition of argon to the O2/CF4 gas mixture unexpectedly leads to an increase in etch rate by a factor of at least two. Moreover, the optimum O/F ratio decreases by a factor of three and, correspondingly, the optimum CF4 mole fraction decieases. Analysis of oxygen and fluorine densities suggests argon metastables alter the homogeneous chemistry for fluorine atom production as well as the heterogeneous chemistry of photoresist chain scission. Overall activation energies are 10.6, 10.8, 4.1 and 0.7 kcal/mole for O2, Ar/O2, O2/CF4 and Ar/O2/CF4 mixtures, respectively. The optimal CF4 mole fraction increases with increasing substrate temperature. A Hougen-Watson model for the heterogeneous chemistry on the wafer surface reproduces the data very well.

The Effect of Argon Addition on the Microstructure, Texture and Phases of Silicon Carbide Prepared by Chemical Vapor Deposition

Silicon carbide was chemically deposited on the (111) surface of silicon single crystal and isotropic pyrolytic graphite by using methyltrichlorosilane as source gas. The deposits were examined by X-ray diffractometry and electron scanning microscopy (SEM) and found to be composed of β-SiC, free Si and a trace of 2H-SiC. The coatings yielded the less free silicon in it using graphite as substrate and at a higher argon flow rate. X-ray analysis indicated that the degree of preferred orientation varied with the kinds of substrate materials and the amount of argon added.

Fracture analysis of soldered wire by plasma ashing and SEM

The increasing demand for higher quality and reliability in the computer peripherals industry requires that the components function without premature materials failure. SEM has been found to be an indispensable technique for studies leading to improved materials and processes. Because of the variety of materials used, SEM specimen preparation requires continuing innovation.Low temperature oxygen plasma-ashing was found to be a convenient technique to remove organic resins and other hydrocarbons. A gaseous plasma, consisting of neutral, energized and ionized atoms, is created by sending oxygen through a high voltage electric field. The plasma readily reacts with the hydrocarbons forming gaseous carbonaceous by-products. The addition of argon to oxygen provides sputter-etching and a more effective resin removal. The temperature of the specimen rarely goes above 50°C and so it is called low temperature gas plasma. The plasma does not alter surfaces or bulk properties of metals and ceramics.

The Effect of Neon and Argon Additions on Improving Selectivities in the Helium Afterglow Discharge Detector

The ultraviolet (UV) spectra of the helium (He) afterglow and mixed gas helium-neon (He-Ne) and helium-argon (He-Ar) afterglows are presented. The effect of Ne and Ar on the He afterglow background spectrum and on the selectivities (versus carbon) for sulfur and phosphorus detection in the UV region is discussed.

Profile Control Possibilities for a Trench Etch Process Based on Chlorine Chemistry

For etching trenches in single‐crystal silicon, dry etch systems with different chamber geometries and chemistries are used. In this work the influence of the etch parameters and the oxide mask on the trench profile is investigated using a triode reactor system with chlorine as the reactive gas and additions of argon and nitrogen. It is shown that there are several possibilities for adjustment of the trench profile even if a heavily doped buried layer has to be etched. It is also demonstrated that unsymmetrical trenches or even sidewall trenching are caused by an unsuitable oxide mask.

Characterization of the Plasma Chemistry and Film Composition of PECVD Silicon Nitride Deposited from Silane-Nitrogen and Silane-Ammonia Mixtures with Argon Additions

AbstractSilicon nitride films deposited from silane-nitrogen and silane-ammonia mixtures by PECVD contain large amounts of hydrogen. We have determined that adding argon to the gas mixture reduces the amount of hydrogen in the resulting films. Differences in film composition are obviously due to changes in the chemistry of the discharge which was characterized by line-of-sight mass spectrometry, optical emission spectroscopy and plasma double probe measurements. Substrate temperature was fixed at 325°C, pressure was 500 mtorr, the RF power was 0.25 watts cm−2, the silane to nitrogen ratio was varied from 0.003 to 0.02, the silane to ammonia ratio was varied from 0.01 to 0.5, and the argon additions were 10% of the total gas flow. Argon additions to the discharge increased the plasma density in both nitrogen and ammonia plasmas. Optical emission from N2 and Si-H species increased upon the addition of 10% argon to the silane-nitrogen discharge, whereas the N-H emission decreased upon addition of argon to the silane-ammonia discharge. Infrared transmission spectra of films deposited with and without argon show no change in peak position or intensity of Si-H and N-H absorption bands in the spectral range studied, despite a large (over 20%) reduction in hydrogen content, as determined by nuclear profiling, upon the addition of argon. These results suggest that a substantial fraction of the hydrogen in the films is not infrared active. We propose that the reduction in hydrogen content is due to bombardment of the growing film by argon ions, which sputter the adsorbed hydrogen molecules.

Transport coefficient calculation in air-argon mixtures: explanation of the improvement of detection limits of pollutants in air inductively coupled plasmas by argon addition

To explain the improvement of detection limits of some atmospheric pollutants that result from the addition of a small quantity of argon to air inductively coupled plasmas, transport coefficients of air-argon mixtures were calculated. These coefficients are introduced in a simplified energy balance equation: as a general rule, introduction of a small amount of argon in an air discharge introduces an increase of the temperature due to the decrease of energy losses by thermal conduction; the intensity of spectral lines of the analyte is then increased.

Non-thermal rotational and vibrational excitation of CN produced in the flash photolysis of thiazole

In the flash photolysis of thiazole at low pressure without any diluent, the 0–0, 1–1 and 0–1 bands of the CN violet system were observed in absorption; the 0–0 band at 3883·4 A showed a high rotational excitation corresponding to a temperature of ⋍2000 K. The addition of argon makes the NCS bands appear with good intensity and at the same time relaxes the CN rotationally and vibrationally. These observations suggest that highly excited NCS is initially formed in the photodecomposition of thiazole which acted as a precursor to the rotationally and vibrationally excited CN radical. This paper deals with studies on the effect of argon on the relative intensities of CN and NCS and on the non-thermal rotational and vibrational intensity distribution of the CN violet system. The mechanism of formation of rotationally unrelaxed CN in the flash photolysis of thiazole has been proposed.

Investigation of lasing in neon pumped by a self-sustained discharge preionized by ultraviolet radiation

An experimental investigation was made of lasing in neon at λ = 540.1 and 585.3 nm when this gas was pumped by a transverse discharge. At λ = 540.1 nm the duration of the laser pulses was 35 nsec. The addition of argon to an He–Ne–H2 mixture pumped by a self-sustained discharge increased the duration of the output pulses at λ = 585.3 nm.

IR fluorescence studies of the IR multiple-photon dissociation of the system CDF 3-CHF 3

Time-resolved IR emissions were obtained for IR multiple-photon excitation/dissociation of CDF 3 at 970 cm −1 in neat form and its mixtures with CHF 3 and argon at moderate pressures. Enhancements in emission intensities were observed for CDF 3 * and DF * on addition of argon. The bimodal exponential decay observed for both CDF 3 * and DF * emissions in the neat photolysis of CDF 3 changed into single-mode decay when the sample was irradiated in the presence of argon at a focal fluence of 95 J cm −2. The bimolecular rate constant for collisional deactivation of CDF 3 * by argon was 1.3 × 10 3 s −1 Torr −1. In situ selectivity factors were determined from the measurements of DF * and HF * emission intensities in the photolysis of 1:1 CDF 3-CHF 3 mixtures.

The influence of argon addition on the deposition and properties of Si:H, Cl films prepared in a glow discharge

Thin silicon films produced in r.f. glow discharges fed with SiCl 4-H 2 mixtures are studied. The effect of argon addition to the feed is examined. Emission spectroscopy and laser interferometry were used to correlate some kinetic parameters, such as the deposition rate, with chemical, optical and structural properties of the deposited material. An overall film growth mechanism is suggested in which chemisorbed species and hydrogen atoms play an important role.

Structure and chemical composition of glow discharge Si:H,Cl films. The role of gas phase argon addition.

Hydrogenated and chlorinated silicon films have been deposited in radiofrequency, capacitively coupled, glow discharge fed with SiCl 4-H 2-Ar mixtures. The presence of argon strongly affects the structure and the chemical composition of the material; in a well defined range of Ar:H 2 ratio a purely amorphous material can be deposited. At high values of Ar addition a transition deposition-etching is observed.

Effect of argon addition to SiCl 4-H 2 mixtures on the optical properties of glow discharge silicon films

Results of investigations of the optical properties of amorphous and microcrystalline Si:H, Cl films obtained from an SiCl 4-H 2-Ar glow discharge are reported. It was found that both the crystallinity and the impurity content (hydrogen and chlorine), which are important in determining the optical properties, are strongly influenced by the addition of argon. In particular, a marked effect of the crystalline grain size on the degree of disorder is found.

Evidence of crystallographic etching in (100)GaAs using SiCl4 reactive ion etching

Etch rate and etch profile characteristics of (100)GaAs in SiCl4 reactive ion etching have been studied in the pressure range of 2–110 mTorr. Pronounced crystallographic or orientation dependent etching effects were observed at moderate pressures around 20 mTorr at lower power densities. Etch profiles became vertical at lower pressures. Therefore, pattern profiles with perfectly vertical sidewalls or with sidewalls defined by crystallographic planes can be realized merely by changing the etch conditions. The addition of argon to the etch gas increased the edge sharpness of the vertical profiles and eliminated any trace of orientation dependent etching. Sawtooth gratings and submicrometer structures with high aspect ratios have been fabricated.

Infrared Multiphoton Induced Isomerization of cis‐3,4‐Dichlorocyclobutene. III. Pressure Dependence of the Yield

AbstractThe multiphoton induced isomerization of cis‐3,4‐dichlorocyclobutene (DCCB) was studied as a function of pressure. Three experiments indicated the existence of a nonthermal mechanism at neat pressures below 60 mtorr. These were: (i) the leveling off of the fractional yield of isomerization products at low pressures; (ii) the absence of dissociation products from 2‐iodo‐2‐methyl propane, which served as a chemical thermometer in the presence of a large excess of DCCB; and (iii) a break in the power‐law dependence of the optoacoustic signal produced by neat DCCB. The increased yield at higher DCCB pressures is believed to be due partly to a thermal reaction and partly to increased absorption caused by rotational or vibrational hole filling. Optoacoustic measurements also showed that at constant fluence the absorbed energy was greater for long, low intensity pulses, as might be expected for inhomogeneous excitation. However, the present experiments did not reveal an intensity dependence of the reaction yield. Addition of argon as a buffer gas monotonically decreased the yield, indicating that vibrational quenching more than offsets any hole‐filling effects.

Carbon dioxide laser photolysis of mixtures of dichlorofluoromethane-h and -d

Dichlorofluoromethane-h (CHCl/sub 2/F) weakly absorbs the CO/sub 2/ laser radiation of the 10.6-..mu..m P(20) line at 944.2 cm/sup -1/, while dichlorofluoromethane-d (CDCl/sub 2/F) has a large absorption coefficient at this wavenumber. The isotope selectivity and specific decomposition yields for the infrared multiple-photon dissociation (IRMPD) of mixtures of CHCl/sub 2/F and CDCl/sub 2/F have been examined as the functions of various experimental parameters such as reactant pressure, argon pressure, laser intensity, and irradiation temperature. The isotope selectivity was found to decrease considerably with increasing partial pressure of the resonant molecule CDCl/sub 2/F. However, the isotope selectivity was rather insensitive to the partial pressure of the off-resonant molecule CHCl/sub 2/F. The addition of argon resulted in an increase in selectivity without decreasing the specific decomposition yields. A reaction mechanism for isotope scrambling was proposed. 9 figures, 2 tables.

Formation and reactions of negative ions relevant to chemical ionization mass spectrometry. I. CL mass spectra of organic compounds produced by F- reactions.

A systematic study of the negative-ion chemical ionization mass spectra produced by the reaction of F(-) with a wide variety of organic compounds has been accomplished. A time-of-flight mass spectrometer fitted with a modified high pressure ion source was employed for these experiments. The F(-) reagent ion was generated from CF(3)H or NF(3), typically at an ion source pressure of 100 mum. In pure NF(3), F(-) is the major ion formed and constitutes more than 90% of the total ion intensity. While F(-) is also the major primary ion formed in pure CF(3)H, it undergoes rapid ion-molecule reactions at elevated source pressures, yielding (HF)(n)F(-) (n = 1-3) ions, which makes CF(3)H less suitable as a chemical ionization reagent gas. Among the organic compounds investigated were carboxylic acids, ketones, aldehydes, esters, alcohols, phenols, halides, nitriles, nitrobenzene, ethers, amines and hydrocarbons. An intense (M - 1)(-) ion was observed in the F(-) chemical ionization mass spectra of carboxylic acids, ketones, aldehydes and phenols. Alcohols yield only (M + F)(-) ions upon reaction with F(-). A weaker (M + F)(-) ion was also detected in the F(-) chemical ionization spectra of carboxylic acids, aldehydes, ketones and nitriles. The F(-) chemical ionization mass spectra of esters, halides, nitriles, nitrobenzene and ethers are characterized primarily by the ions, RCOO(-), X(-), CN(-), NO(2) (-), and OR(-), respectively. In addition, esters show a very weak (M - 1)(-) ion (except formates). In the F(-) chemical ionization spectra of some aliphatic alkanes and o-xylene, a very weak (M + F)(-) ion was observed. Amines and aliphatic alkenes exhibit only insignificant fragment ions under similar conditions, while aromatic hydrocarbons, such as benzene and toluene are not reactive at all with the F(-) ion. The mechanisms of the various reactions mentioned are discussed, and several experimental complications are noted. In still other studies, the effects of varying several experimental parameters, including source pressure, relative proportions of the reagent and analyte, and other ion source parameters, on the observed chemical ionization mass spectra were also investigated. In a mixture of NF(3) and n-butanol, for example, the ratio of the intensities of the ions characteristic of the alcohol to that of the (HF)(n)F(-) ion was found to decrease with increasing sample pressure, with increasing NF(3) pressure, and with increasing electron energy. No significant effects on the spectra were observed to result from variation of the source repeller field or the source temperature. The addition of argon to the source as a potential moderator did not alter the F(-) chemical ionization spectrum significantly, but the use of oxygen appears to inhibit formation of the (HF)(n)F(-) cluster ion. The advantages of using F(-) as a chemical ionization reagent are discussed, and comparisons are made with other reagent ions.

Molecular theory of multilayer adsorbed films

The detailed molecular information made available by a computer simulation of multilayer adsorption of argon on graphite is used to develop an augmented form of Frenkel—Halsey—Hill (F.H.H.) theory. The distinctive feature of the present study is that addition of argon to the system at moderate coverages is described as simultaneous addition of atoms to several different adsorbed layers. A modified F.H.H. isotherm equation is obtained which is in better agreement with the simulated data than is the standard F.H.H. theory. A theoretical analysis of the chemical potential of very thick films is also carried out which takes account of the finite thickness of the interface between adsorbed film and vapor. A correction term is added to the F.H.H. equation for very thick films which helps to explain the observed discrepancies between experiment and theory.

Negative ion mass spectrometry: The generation of high concentrations of low energy molecular negative ions at high source pressures

AbstractThe effect of the addition of argon and other gases upon the intensities of negative ion species formed in an electron impact source has been investigated. The negative ion current generated for a series of aromatic compounds has been investigated as a function both of sample and argon pressure in the ion source of a ZAB‐2F mass spectrometer. For all compounds studied, a striking enhancement of molecular negative ion current occurred on increasing either the presure of the sample or of argor. The results are consistent with thermalization of the 50 eV electrons by collisions with neutral molecules in the high pressure ion source and collisional stabilization of the negative ions initially formed. Analytical applications of the technique are discussed.