Browse - Journal of Vacuum Science & Technology Archives 1964-1982

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An Absolute Micromanometer Using Diamagnetic Levitation

R. Evrard and G.-A. Boutry

J. Vac. Sci. Technol. 6, 279 (1969); http://dx.doi.org/10.1116/1.1492679 (10 pages) | Cited 3 times

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A friction-free suspension in vacuo is provided for a graphite disk by magnetic induction. The disk rotates round a vertical line of force inside a properly designed stator; when the stator is cooled, a thermomolecular torque is developed and the acceleration thus given to the disk is measured by an automatic device. It is shown that this acceleration depends only on the geometrical design of the manometer and on the pressure, to which it is proportional. The manometer unit is passive, very small, and insensitive to vibrations and shocks affecting the vacuum setup. The lower limit of its range of measurement is less than 10⁻¹⁰ Torr. When stator cooling is removed, the disk is influenced only by a (smaller) molecular damping torque. This depends on the composition of the residual atmosphere; provided this is known, the magnitude of the damping can be computed a priori with good precision so that the instrument becomes a useful standard manometer for calibration in the 10⁻³ to 10⁻⁷ Torr range.

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07.30.Dz

Vacuum gauges

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Destructive Breakdown in Thin Films of SiO, MgF₂, CaF₂, CeF₃, CeO₂ and Teflon

Paul P. Budenstein, Paul J. Hayes, J. Lynn Smith, and Wallace B. Smith

J. Vac. Sci. Technol. 6, 289 (1969); http://dx.doi.org/10.1116/1.1492680 (15 pages) | Cited 14 times

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Prebreakdown and breakdown electrical properties, and also the light emitted during destructive breakdown, have been studied in thin-film capacitors with the dielectrics SiO, MgF₂, CaF₂, CeF₃, CeO₂, and Teflon. Capacitors were formed on glass substrates and had dielectric thicknesses from 900 to 16000 Å. At temperatures between 80 and 380 K, breakdown characteristics are found to be independent of prebreakdown ac and dc conduction. All of the materials studied show a threshold field for the onset of breakdown (on the order of 10⁶ V∕cm) that is almost temperature independent and varies with dielectric thickness w approximately as w^−1∕2. All materials also have a threshold voltage for the cessation of breakdown which is typically between 10 and 20 V. The light emitted during breakdown contains the arc spectra of the dielectric and the two electrodes. Intensity of single wavelengths of light were recorded simultaneously with voltage waveforms and show that all lines are emitted from the very beginning of breakdown conduction. Hence, breakdown conduction is due to the formation of a gaseous arc. This arc, formed in less than 10⁻⁸ sec, carries the high current characteristic of breakdown and causes destruction of the dielectric.

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77.22.Jp	Dielectric breakdown and space-charge effects
84.32.Tt	Capacitors
77.55.-g	Dielectric thin films

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Inert Gas Ion Pumping Using Differential Sputter Yield Cathodes

T. Tom and B. D. James

J. Vac. Sci. Technol. 6, 304 (1969); http://dx.doi.org/10.1116/1.1492681 (4 pages) | Cited 3 times

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A method to eliminate “argon instability” in a Penning cold-cathode ion pump is proposed. This method involves the use of a metal having a high sputtering yield coefficient as one of the cathodes. The results obtained using titanium and tantalum as cathodes are described. This combination has eliminated the pressure fluctuations while pumping inert gases. The performance characteristics on gases such as air, nitrogen, hydrogen, argon, and helium are also given.

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07.30.Cy

Vacuum pumps

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Sputtered Silicon–Chromium Resistive Films

Robert K. Waits

J. Vac. Sci. Technol. 6, 308 (1969); http://dx.doi.org/10.1116/1.1492682 (8 pages) | Cited 7 times

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The resistivity, temperature coefficient of resistance (TCR), and structure of annealed films deposited by de diode sputtering have been studied as a function of chromium content over the range 17–33 at.% Cr. The resistivity decreases from 0.1 to 0.001 Ω cm and the TCR changes from −1500 to +500 ppm∕°C with increasing Cr content. Films containing about 27 at.% Cr had the lowest TCR. Films deposited at a cathode potential of 10 kV have a more positive TCR for the same resistivity than films sputtered at 2.5 kV. Electron micrographs showed the latter films to have a coarser structure—due either to a larger grain size (150 Ă compared to 50 Å) or to a clumping of grains. Electron diffraction patterns indicated a nearly amorphous film; CrSi₂ was the only identifiable phase. The average drift of 50 μm-wide resistors (1 to 25 kΩ∕square) during 1800 h at 200 °C (no load) or 125 °C (50 V dc) was ±0.5% after an initial 200 h aging under the same conditions.

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73.61.-r	Electrical properties of specific thin films
68.55.-a	Thin film structure and morphology
81.15.Cd	Deposition by sputtering

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Hydrogen Pumping Speed of Sputter-Ion Pumps

J. H. Singleton

J. Vac. Sci. Technol. 6, 316 (1969); http://dx.doi.org/10.1116/1.1492683 (6 pages) | Cited 3 times

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The pumping speed of a sputter-ion pump for hydrogen may vary over a wide range. At procures below 10⁻⁸ Torr the speed decreases rapidly and cannot be explained as a simple decrease in the discharge current. In the pressure range between 10⁻⁸ and 10⁻⁶ Torr the pumping speed for pure hydrogen is of the same order as that for nitrogen. However, if a second gas having a higher sputtering yield for titanium is also present in sufficient concentration, increases of at least a factor of two are observed in the pumping speed for hydrogen. Finally, at hydrogen pressures above 10⁻⁶ Torr the long-term pumping of pure hydrogen can produce a marked increase in speed. The extent of this increase is reduced by the presence of active gases such as nitrogen, indicating that change of the rate of diffusion of hydrogen into the titanium at room temperature is the principal factor involved.

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07.30.Cy

Vacuum pumps

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Buried Collector Gauge for Measurements in the 10⁻¹¹ Torr Pressure Range

Leonard T. Melfi,

J. Vac. Sci. Technol. 6, 322 (1969); http://dx.doi.org/10.1116/1.1492684 (4 pages)

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A nude ionization gauge is described in which a shielded collector is used to lower the x-ray current. Pressures as low as 4×10⁻¹² Torr have been indicated with an estimated x-ray current corresponding to a pressure below 2.6×10⁻¹² Torr. Calibration of the gauge on an orifice flow-rate system in the pressure range between 10⁻⁶ and 10⁻⁹ Torr with 4-mA emission and a collector to filament voltage of −300 V, yielded a gauge constant of 20 Torr⁻¹. For pressure below 10⁻⁹ Torr the buried collector gauge was compared to the bent-beam Helmer gauge. Data from tests performed on the bent beam Helmer gauge are also given. These include a calibration and a plot of gauge constant as a function of emission current in the range between 0.1 and 10 mA.

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07.30.Dz

Vacuum gauges

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Theory of Pulsed Molecular-Flow Networks

B. R. F. Kendall and R. E. Pulfrey

J. Vac. Sci. Technol. 6, 326 (1969); http://dx.doi.org/10.1116/1.1492685 (7 pages) | Cited 1 time

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A general molecular-flow network theory applicable to volumes interconnected by small orifices or porous membranes is discussed. Parameters which describe the properties of such orifices and membranes are first defined. Basic theory is then extended to cover operation with mixtures of gases having different molecular weights. Characteristics of several networks with pulsed pressure inputs are then derived. It is shown that the mass-dependent resistance to flow of an orifice or porous membrane makes it possible to use certain molecular-flow networks as gas analyzers. Other networks are described which have potential applications in improving gauge response to rapid pressure fluctuations.

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77.55.-g	Dielectric thin films
77.22.-d	Dielectric properties of solids and liquids
81.15.-z	Methods of deposition of films and coatings; film growth and epitaxy

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Dielectric Properties of Reactively Evaporated Silicon Monoxide

Thomas A. Anastasio

J. Vac. Sci. Technol. 6, 333 (1969); http://dx.doi.org/10.1116/1.1492686 (5 pages) | Cited 1 time

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Dielectric constant and dissipation factor for films formed by the reactive evaporation of silicon monoxide in oxygen have been measured as a function of deposition rate, oxygen pressure, electrode material, substrate temperature during evaporation, and source temperature. The dielectric properties are shown to depend primarily on the ratio of molecular impingement rates at the substrate of O₂ and SiO (p∕r), independent of substrate temperature and electrode material. Dissipation factor, but not dielectric constant, is strongly dependent on source temperature. Some dc conductivity and capacitor discharge characteristics are related to the p∕r parameter.

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77.55.-g	Dielectric thin films
77.22.-d	Dielectric properties of solids and liquids
81.15.-z	Methods of deposition of films and coatings; film growth and epitaxy

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Application of the Triple Grid LEED System to Auger Spectrum Analyses

J. Morrison and J. J. Lander

J. Vac. Sci. Technol. 6, 338 (1969); http://dx.doi.org/10.1116/1.1492687 (3 pages)

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68.37.Xy	Scanning Auger microscopy, photoelectron microscopy
61.05.jh	Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)