摘要:

This Recommended Practice addresses issues involved in the use of partial pressure analyzers (PPAs) for quantitative analysis and describes recommended apparatus and procedures for determining resolution and sensitivity of a PPA so that the instrument can be used quantitatively for partial pressure, partial flow and gas composition analysis. This updates previous material in the AVS Standard 2.3-1972 (tentative) by including reference to current pressure transfer standards and computer controlled PPAs. This document presents an introduction to PPAs and how they work, definitions pertinent to the use of PPAs, equipment needed for calibration, instrument setup prior to calibration and the measurement of sensitivity and linearity by various methods. Four methods of calibration of a PPA are described as follows: (1) the direct comparison of the PPA output with a transfer standard pressure gauge, (2) the indirect comparison of PPA readings with readings of a transfer standard pressure gauge separated by a flow restriction (pressure divider method), (3) comparison of the PPA output response to known gas flow rates. The first three methods may be carried out on a test stand of suitable design orin situ.The fourth method requires that the pumping speed during calibration be the same as the pumping speed during use, and normally implies that the PPA is calibratedin situ.Discussion on gas interactions, sources of nonlinearity, stability of sensitivity and quality assurance methods is given.

ISSN:0734-2101    

DOI:10.1116/1.4755937

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

The intensities of the diffraction spots for the boron induced √3×√3R30° Si(111) reconstruction in a bulk electron microscope sample examined in ultrahigh vacuum are compared with the results of multislice simulations. The intensities of the spots support the relaxed S5 model. We rule out the existence of any subsurface structure such as the stacking faults present in the Si(111) 7×7 surface.

ISSN:0734-2101    

DOI:10.1116/1.578758

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

In this report we discuss the results of a study undertaken to investigate the composition and thermal stability of ultraviolet/ozone oxidized, P2S5/(NH4)2S treated GaAs(100) surfaces. In particular, we have used x‐ray photoelectron spectroscopy and Auger electron spectroscopy to probe the oxide and interface at room temperature and as a function of annealing temperature. The room temperature data indicate that S is buried between the oxide overlayer and the GaAs substrate. This oxide contains a variety of As and Ga bonding configurations which, after moderate annealing, are transformed into thermally more stable phases, such as As2O3and Ga2O3 . Complete desorption of the oxide occurs after annealing at 600 °C. Annealing the as‐oxidized surface to high temperatures also has a profound effect on the S. Heating the sample to 495 °C causes some S to diffuse towards the oxide surface, while annealing at higher temperatures leads to S diffusion into the GaAs substrate. Even after complete desorption of the O, a small amount of S remains embedded in the GaAs lattice.

ISSN:0734-2101    

DOI:10.1116/1.578759

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

A study on a model system for polymer–metal interface formation after surface treatment is presented. We discuss a comparative x‐ray photoelectron spectroscopy analysis ofinsituplasma and ion‐treated polypropylene surfaces with an evaporated magnesium overlayer. The different surface treatments are found to enhance the sticking probability of the metal vapor on the polymer surface considerably. Depending on the kind of surface treatment, different types of bonding of the Mg with the polymer are observed. The analysis of the excited plasmons is used to gain information about the interface formation. The experimental results suggest an island growth mode of the Mg.

ISSN:0734-2101    

DOI:10.1116/1.578760

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

This research has performed preliminaryinsituFourier transform infrared (FTIR) measurements during the plasma deposition of amorphous silicon (a‐Si:H). Experiments demonstrate both gas phase and film measurements within a simple SiH4plasma reactor using a specially modified FTIR spectrometer. Films are deposited on substrates of either gold (mirror finish) or stainless steel (matte finish). In particular,insituemission/reflection FTIR of the film yields information about surface temperature, film thickness, and film composition. We have measured surface temperature to ±5 K and detected the onset of poor film growth at a thickness of 500–1000 Å using the 2080 cm−1absorption feature. A simple model for the reflectance of a film on a metal is employed to determine the thickness of the films.Insituemission/transmission FTIR of the plasma determines the gas composition and average gas temperature. Measurements show that the silane conversion is ∼11% within the plasma region for a typical deposition at 250 °C and roughly doubles for a deposition at room temperature. The FTIR spectra show that most of this converted silane reappears as disilane (Si2H6). Before starting the plasma, the silane gas is ∼30 K cooler than the nominal substrate temperature of 250 °C; starting the plasma raises the average temperature another 20 °C.

ISSN:0734-2101    

DOI:10.1116/1.578761

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

A new technique of applying a high frequency discharge for redistribution of solid deuterium–deuterium (D2) or deuterium–tritium (DT) fuel in a laser fusion target is proposed for future reactor‐class targets. This technique can enhance the beta decay technique which has a long time constant for redistribution of the fuel far below the triple point. A plasma initiated in the central void of the target by glow discharge uniformly heats the inner surface of the fuel ice, and the target is located in an isothermal cooling medium. Resultant higher temperatures at a thicker fuel ice area induce sublimation of the thick fuel ice and condensation of the vapor on a thinner, cold area. This technique is applicable to deuterium fuel in a shell for current implosion experiments. A proof of principle was demonstrated by using krypton gas and liquid nitrogen as substitutes for the D2or DT fuel and liquid helium, respectively. A smooth solid krypton layer was formed in a glass shell with a gas feeder.

ISSN:0734-2101    

DOI:10.1116/1.578763

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

We report on our efforts to apply Rutherford backscattering spectrometry (RBS) for measuring the permeation of fluorine into low (LDPE) and high density polyethylene (HDPE) that have been exposed to gas atmospheres containing fluorine. To address the issue of sample damage during RBS analysis, experimental conditions were chosen using polytetrafluoroethylene as a standard. Our studies of LDPE and HDPE containers exposed to 1% fluorine in nitrogen atmospheres show the depth of fluorine penetration to be approximately 400 Å. Though the depths of treatment for both materials are quite similar, we find that the amount of fluorine uptake per unit volume is significantly higher for LDPE. The information yielded by RBS (depth of treatment and uptake per unit volume) shows it to be a powerful method for evaluating surface and near surface treatments of polymeric materials.

ISSN:0734-2101    

DOI:10.1116/1.578764

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

Deposition of carbon nitride thin films on Si(100) and polycrystalline Zr substrates was performed by dc magnetron sputtering of a graphite target under a pure nitrogen ambient. The resulting carbon nitride films (CNx) are primarily amorphous with a small volume fraction of nanocrystallites. Both energy‐dispersive x‐ray analysis and electron energy loss spectroscopy measurements showed that the amorphous matrix has uniform nitrogen‐to‐carbon ratios ∼0.4–0.8 depending on deposition conditions. Carbon and nitrogenKedge structures obtained from electron energy loss spectroscopy studies suggest that the amorphous carbon nitride matrix is primarilysp2bonded. Apart from the carbon–nitrogen stretching vibration, Raman spectra of CNxfilms closely resemble those of diamondlike carbon films. Intensity and peak width changes of Raman features in the 1300–1600 cm−1range due to inorganic carbon (DandGpeak) under different deposition conditions are explained in terms of the extent of structural disorder in these films.

ISSN:0734-2101    

DOI:10.1116/1.578765

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

This article reports structural and electronic properties of sodium adsorbed on room‐temperature GaAs(110) surface as observed with scanning tunneling microscopy in an ultrahigh vacuum. In the low‐coverage regime, Na adatoms reside on the bridge site encompassing one Ga and two As surface atoms to form linear chains along the [11̄0] direction. The Na–Na nearest‐neighbor distance in this low‐density chain structure is 8 Å. When the Na coverage was increased to ∼0.09 ML (1 ML≡2 Na per substrate unit cell), the chains became slightly disordered. Some of them were packed closer to form domains with local 2×2 structure. None of high‐density two‐dimensional ordered structures or low‐density zigzag chains was observed, in contrast to the Cs/GaAs(110) system. Additional Na adsorption resulted in the formation of three‐dimensional disordered clusters. The saturation coverage of Na adsorption on the GaAs(110) surface was determined to be ∼0.1 ML. No evidence of metallic characteristics was found in theI–Vcurves recorded over the various Na‐covered surfaces.

ISSN:0734-2101    

DOI:10.1116/1.578766

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

Normal and off‐normal photoemission are performed in the 16–27 eV range on Cd0.6Hg0.4Te mixed crystal. The umklapp bands, well recognized on normal incidence energy distribution curve, can be followed in off‐normal data, with continuous variations not previously observed. A tight binding calculation of the energy dispersion of the umklapp bands confirms that most secondary emissions are in fact related to umklapp bands. The surface states appear partly masked by these bulk derived umklapp bands. Only one surface state, in an inner gap of the valence band, appears distinct from other bulk features, which indicates that some of the previously mentioned experimental surface states in II–VI compounds should be revised.

ISSN:0734-2101    

DOI:10.1116/1.578767

出版商:American Vacuum Society    

年代:1993

数据来源: AIP