摘要:

A comparison of the vacuum standard maintained by four laboratories within the European Community (Istituto di Metrologia ’’G Colonetti’’ Turin, Italy; Laboratoire de Metrologie, Leybold–Heraeus–Sogev, Valence, France; National Physical Labortory, Teddington, Great Britain and Physikalisch–Technische Bundesanstalt, Berlin, Federal Republic of Germany) has been made in the pressure range 8×10−5Pa to 8×10−2Pa using a JHP high pressure ionization gauge. Three gauges were circulated around the participating labortories, each laboratory carefully following a detailed procedure for the preparation and operation of the gauge so as to minimize random variations in the sensitivity coefficient of the gauge. The gauges were calibrated up to nine times at each pressure by all the laboratories, the measurements in each laboratory taking place over a period of three days. A statistical analysis has been performed which shows that the standard of each of the labortories does not differ from the weighted mean of all the standards by more than ±2%. The results also show that when the three JHP gauges were used in the carefully controlled manner described in this paper, the ionization gauge coefficient did not change from its initial value by more than ±1.7% over an 18 month period.

ISSN:0022-5355    

DOI:10.1116/1.570541

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

Stability of the exciting electron beam is critical in spectrometries such as Auger electron spectrometry when, for example, line‐shaped studies or quantitative analysis is performed. The beam from an electron gun can be stabilized by feedback control referenced directly to the beam current at the operating acceleration potential. This is accomplished by measuring the beam current and providing to the electron gun a voltage proportional to the current in such a manner as to oppose any change in the beam current. A system employing this method has been constructed and tested with an Auger electron spectrometer using a retarding‐grid energy analyzer. A considerable improvement in beam stability was achieved permitting long data acquisition periods necessary to improve signal−to −noise of spectra for Auger analysis. This method of beam control has proven to be superior to conventional systems employing constant grid current or grid voltage regulation.

ISSN:0022-5355    

DOI:10.1116/1.570542

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

The four elliptic emission functionsv(y),t(y),s(y) and ϑ(y) [orfmg(y)] are used in calculating electron emission from surfaces under the influence of temperature and external electric fields. Critical evaluations are made of the published tables of these functions. Several existing approximation equations for the emission functions are given together with some additional polynomial approximations. The estimated accuracies of these approximation equations range from five to six significant figures for the most complex approximations to ±1% or so for the simplest.

ISSN:0022-5355    

DOI:10.1116/1.570543

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

The ambient temperature outgassing rate of several multilayer insulation materials has been measured for evacuation times of about six days. The material tested included Mylar radiation shields, double and single metallized with aluminum and gold; double and single aluminized Kapton radiation shields of different thicknesses; and three net and two glass fiber‐cloth spacer materials. Experimental measurements were made by collecting outgassing flux from an effusion cell‐type sample holder on a liquid‐nitrogen‐cooled quartz crystal microbalance. The absolute accuracy, measurement range, degree of resolution, and other features of this technique are discussed in detail. The physical phenomena controlling outgassing rate are discussed. It is concluded that long‐term outgassing of the metallized shields is probably controlled by degassing of the metallized surfaces. On this assumption empirical equations are proposed for estimating long‐term outgassing rates. Data from previous measurement programs are evaluated and compared with the new data as a standard.

ISSN:0022-5355    

DOI:10.1116/1.570544

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

Outgassing data is introduced for some circumjacent cellular materials and stranded elastic cords used for the shock mitigation of experiments in chambers evacuated to 1 mTorr. The influence of area/volume configuration ratios and the effect of humidity sorption on carbonaceous foam outgassing is shown for pumpdown elapsed‐time durations to 10 h, and for A/V ratios from 0.4 to 0.8 cm−1. Combined outgassing and virtual leakage data, from test specimens which were loosely wrapped to control carbon foam particle migration and vacuum pump oil contamination, is discussed. Other test specimens investigated, which had A/V ratios from 0.4 to 4.2 cm−1, are polyurethane foam, aluminum–alloy honeycomb, elastic shock absorber (bungee) cord, and distended‐surface steel plate. A cascading chart is presented for lucid determination of outgassing rates from these materials. Outgassing coefficients developed from this data for modeling are referenced.

ISSN:0022-5355    

DOI:10.1116/1.570545

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

A versatile UHV apparatus is described which permits large (up to 10×10 cm) sample arrays or entire experiments to be inserted from air into an operating tokamak. This can be accomplished without perturbing the tokamak vacuum. Samples or experiments may be exposed in the tokamak for studies of plasma‐wall interactions and removed at any time without requiring tokamak shutdown. Samples or experiments may be accurately positioned in the region between the vacuum wall and the plasma limiter remotely. The apparatus provides up to 20 electrical connections for thermocouples, heaters, and signal leads. It also provides linear and rotary mechanical motion for operating experiments sychronized to tokamak discharges. Experiments or samples may be prepared off site and loaded into the transfer system under vacuum. A surface analysis station integral with the transfer system permits individual sample preparation, characterization, and analysis before and after plasma exposures.

ISSN:0022-5355    

DOI:10.1116/1.570546

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

Basal planes of hexagonal cadmium sulphide high vacuum deposited on the (111) faces of NaCl single crystals by the hot wall technique have been used for epitaxial deposition of indium phosphide by evaporation of the constituent elements. Two 2‐d{111} orientations, of InP films, 180° to one another were found to develop. Two new hexagonal structures with respectivec0values corresponding to ∠3a0of CdS and ∠√2a0of InP and also a cubic superstructure havinga0equal to 8a0/√3 of InP have been encountered in some instances. The new phases have been attributed to intermixing in the heteroepitaxial films.

ISSN:0022-5355    

DOI:10.1116/1.570547

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

We have used Auger electron spectroscopy and low energy electron diffraction to study the growth of thin platinum films on hydrogenated amorphous silicon (a‐Si:H), its oxide, and on single crystal (111) silicon. We have identified the growth processes as Frank‐van der Merwe ona‐Si:H, Stranski–Krastanov on (111) Si, and (tentatively) Volmer–Weber on

ISSN:0022-5355    

DOI:10.1116/1.570548

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

Plasma etching of polycrystalline silicon films for fabrication of silicon gate MOS integrated circuits has been studied with emphasis on fine‐line devices. CF4–O2plasmas, commonly used for etching silicon, are unacceptable for very fine features because the etching is isotropic and load dependent. This results in substantial undercutting and insufficient dimensional control. Several alternative gases were investigated in a parallel–plate reactor. CF3Cl and a 70% CF3Br–30% He mixture were found to provide selectivities of 30:1 and 16:1, respectively, over thermal SiO2, freedom from loading effects and a large vertical to lateral etch rate anisotropy which minimizes undercutting. Extensive measurements of etch rate and edge profile as a function of gas composition were made for C2F6–Cl2plasmas. Fully anisotropic etching (zero lateral etch rate) was observed at low Cl2concentrations with a selectivity ≳6:1 over thermal SiO2when using conventional photoresist masks. The vertical and lateral etch rates and the selectivity increase with increasing Cl2concentration forn‐type polysilicon. The dependence of etch rate on Cl2concentration forp‐type polysilicon is nearly identical to that for undoped polysilicon, whereasn‐type material etches faster than undoped material with the etch rate ratio (n‐type:undoped) increasing with Cl2concentration. Values for this ratio as large as 15:1 were measured. ’’Pattern sensitivity’’ was observed with photoresist masks such that at low Cl2concentrations etching was slower in the vicinity of resist features while at high Cl2concentrations etching was faster near resist features as compared to open (unmasked) areas of the same film. Pattern sensitivity was negligible at an intermediate Cl2concentration. Results of effluent sampling with IR absorption and mass spectrometry and spectral analysis of optical emission from the plasma suggest that Cl atoms are the likely active species. It is conjectured that the anisotropy in etch rate is a consequence of enhanced chemical reaction between Cl and Si on surfaces which are ion (or electron) bombarded while lateral etching is suppressed by the combination of CF3radicals and Cl atoms on surfaces which are not ion (or electron) bombarded.

ISSN:0022-5355    

DOI:10.1116/1.570549

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

The reactive ion etch rate (RIE) of Al2O3‐based ceramics, in a plasmax reactor with a gas mixture of 5 μm Ar and 2 μm Cl2, is temperature sensitive. The etch rate at room temperature (∠2600 Å/min) is essentially all physical sputtering. ForT=250 °C, the etch rate increase to ∠8200 Å/min. This increase in etch rate is the ’’chemical’’ component of the total etch rate. By means of the same technique, etch rates up to 2.0 μm/min were obtained for Si. In contrast to physical sputtering, RIE of these materials has the advantage that the reaction products are volatile compounds. Redeposition problems should therefore be minimized. In addition, the increase in etch rate obtained by RIE can be used as a trade‐off to optimize other process parameters.

ISSN:0022-5355    

DOI:10.1116/1.570550

出版商:American Vacuum Society    

年代:1980

数据来源: AIP