ISSN:0022-5355    

DOI:10.1116/1.1317063

出版商:American Vacuum Society    

年代:1973

数据来源: AIP

摘要:

Recent experiments were conducted in Langley Research Center's molecular beam system to perform an absolute calibration of the lunar orbital mass spectrometer which was flown on the Apollo 15 and 16 missions. Tests were performed with several models of the instrument using two test gases, argon and neon, in the10−13–10−9Torr range. Sensitivity to argon at spacecraft orbital velocity was2.8×10−4A/Torr enabling partial pressures in the10−14Torr range to be measured at the spacecraft altitude. Neon sensitivity was nearly a factor of 5 less. The response of the instrument to off-axis beams shows a cosine-to-cosine dependence. Test data support the feasibility of using the lunar orbital mass spectrometer as a tool to gather information about the lunar atmosphere.

ISSN:0022-5355    

DOI:10.1116/1.1317064

出版商:American Vacuum Society    

年代:1973

数据来源: AIP

摘要:

A sensitive method of surface composition analysis is obtained through monitoring the binary scattering of low energy noble gas ions from surface atoms. Such analyses have been shown to be accomplished with simplified instrumentation and to be primarily sensitive to the first atomic surface layer. The technique has been extended to include the direct examination of electrically insulating surfaces, and examples of surface compositions obtained from ceramic and glass will be presented. With the capability of examining surfaces irrespective of their electrical conductivity, multilayer thin film structures become a prime example of the dual utilization of the probe ion beam to both analyze and simultaneously controllably remove surface atoms. Such a depth composition profile will be shown for aTiO2thin film sandwich in which interface contamination was found. Quantitative aspects of the technique will be shown in theSiOxsystem. Diverse applications of surface analyses will also be shown on metal, semiconductor, and some select alloy surfaces.

ISSN:0022-5355    

DOI:10.1116/1.1317065

出版商:American Vacuum Society    

年代:1973

数据来源: AIP

摘要:

A new catalytic pump has been proposed for hydrogen pumping in high and ultra-high vacuum, and its performance is estimated from the kinetic processes involved. This pump consists of an incandescent metal filament (atomizing catalyst), a cuprous oxide layer (oxidizer), and a liquid nitrogen trap, in which molecular hydrogen is thermally dissociated into atomic hydrogen at the filament which acts upon the cuprous oxide layer to produce condensable water vapor. The speed of the pump in the molecular-flow region is, in principle, associated with the rate of formation of atomic hydrogen at the filament, which not only is a function of hydrogen pressure and filament temperature, but also depends on the filament material and the surface coverage of other chemisorbed species. From the experimental data, suitable temperatures have been determined to obtain the maximum efficiency against electric power. Iridium and rhenium are found to be good materials for the pump filament.

ISSN:0022-5355    

DOI:10.1116/1.1317066

出版商:American Vacuum Society    

年代:1973

数据来源: AIP

摘要:

A formalism for analytically obtaining an expression for the thermal transpiration pressure ratioRis presented. An experimental parameter σ, which is associated with the type of molecule-solid surface collisions, is introduced. A completely diffuse scattering and a completely specular scattering from a solid surface correspond toσ = 0andσ = 1, respectively. A known distribution function is used to derive a practical formula forRin the case of long tubes and very low pressures. Quantitative results obtained from this formula indicate that deviations from completely diffuse scattering of molecules from solid surfaces give rise to an anomalous Knudsen limit.

ISSN:0022-5355    

DOI:10.1116/1.1317067

出版商:American Vacuum Society    

年代:1973

数据来源: AIP

摘要:

A molecular beam study of the reaction ofC2H4withO2on Ag(111) was attempted and supplemented with data obtained using an isotropic source (IS) configuration. In the beam configuration, the possible product signals at 18 amu (H2O) or 44 amu (C2H4O,CO2) could not be discerned. In the IS configuration, a product signal at 44 amu (CO2) was observed. An estimate of the collision reaction probability of9×10−3, obtained from the IS data, confirmed that the product signal would not be readily observable in the beam configuration due to signal-to-noise considerations. FromC2H4beam scattering data, coupled with the experimental ion spectrum obtained fromC2H4by electron impact, it was possible to estimate that roughly about 15% of the incidentC2H4fragmented upon collision with the surface; 10% going toC2H3and 5% toC2H2. From the surface temperature dependence in the IS configuration, an activation energy of ∼8 kcal/mole was obtained for the mass 44 product.

ISSN:0022-5355    

DOI:10.1116/1.1317068

出版商:American Vacuum Society    

年代:1973

数据来源: AIP

摘要:

A new ionization gauge of an estimated low pressure limit below10−15Torr and of a sensitivity of2×109 Torr−1is presented. The ions, which are produced in an ionizer of conventional design, are extracted through a shield aperture and collected by the funnel-type cathode of a channel electron multiplier. Since the high gain of this multiplier allows the gauge to be operated with an emission current of only several nanoamperes, practically no heat is produced in the gauge. The gauge is mounted on a412-in. flange and has approximately the size of a normal Bayard-Alpert gauge. A general expression for the low pressure limit of hot filament ionization gauges is given. The results as obtained from this expression for gauges of similar geometry are discussed together with the low pressure limit as found for the new gauge.

ISSN:0022-5355    

DOI:10.1116/1.1317069

出版商:American Vacuum Society    

年代:1973

数据来源: AIP

摘要:

The composition of sputtered films can be altered to give desired ferroelectric properties by firing in an atmosphere containing the elements of the required ferroelectric film. These converted films have the pseudocubic provskite-type structure(a0= 4.07 Å)and show the ferroelectric characteristics required for memory applications: square hysteresis loops, pulsed switching and retention of polarization.

ISSN:0022-5355    

DOI:10.1116/1.1317070

出版商:American Vacuum Society    

年代:1973

数据来源: AIP

摘要:

Experiments were performed to determine if oxygen is available on Type 304 stainless steel in a state which could cause oxidation of active metals during hydrogen exposure. A bakeable ultrahigh vacuum system was used in making measurements of hydrogen interaction with stainless steel. Mass spectra were taken throughout the experiments. The experiments indicated that stainless steel reacts in a hydrogen atmosphere to form water. This effect is greater at high than at low temperature. The stainless steel can be passivated by treating the surface with oxygen during heating to high temperature.

ISSN:0022-5355    

DOI:10.1116/1.1317071

出版商:American Vacuum Society    

年代:1973

数据来源: AIP

摘要:

The resistivity, Hall coefficient, and composition of thin films prepared by rf sputtering from a sintered cathode of stoichiometricBi2Te3were measured. Sputtering parameters were varied and affected both composition and resistivity. The polycrystalline films exhibited a strong (101̄5) fiber texture. Resistivity varied from 0.60 mΩ cm to 9.0 mΩ cm over a composition range from 25 wt % Te to 49 wt % Te with the maximum resistivity nearBi2Te3. High carrier concentration and low ionization energies indicate metallic characteristics.

ISSN:0022-5355    

DOI:10.1116/1.1317072

出版商:American Vacuum Society    

年代:1973

数据来源: AIP