Measurements In High Vacuum Research Articles

Just-in-time approach to IC fabrication : Laura Cory. Solid St. Technol., 177 (May 1986)

In the present work, current–voltage (I–V) characteristics of fullerene devices (ITO⧹C60⧹Al) are reexamined by in situ electrical measurement in high vacuum and by infrared imaging analysis. Two kinds of I–V curves are detected: ‘ohmic’ and nonohmic. Degradation processes of the two different devices are measured, and ‘ohmic’ degradation processes are ascribed to short-circuiting. ITO⧹C60⧹Al devices in high vacuum are confirmed to be intrinsically nonohmic. Surface temperature distribution of the two different devices is measured and localized heat is detected further confirming the existence of short-circuiting in ‘ohmic’ devices. To avoid short-circuit, organic buffers are inserted between fullerene layer and cathode and this is found to be effective.

Demonstration of the surface stability of the Van Der Waals surface (0001) of MoSe 2 by LEED and electrochemistry

The Van der Waals surface (0001) of a MoSe 2 crystal was studied by LEED and Auger spectroscopies. Almost no surface reactivity was measured with these techniques upon exposure of the crystal to I 2 vapor, liquid H 2O, 1M HClO 4 and 10 −3M NaI 3. This behavior is in contrast to I 3 − adsorption which has been measured in situ on these surfaces in electrolytes. Electrochemical cycling in various electrolytes, subsequent and prior to the high vacuum measurements, also produced very little change in the composition or structure of the MoSe 2 surface.

Optical absorption in hydrogenated microcrystalline silicon

Optical absorption measurements between 0.35 and 2.5 eV at 22 degrees C on hydrogenated microcrystalline silicon films prepared in a DC discharge at deposition temperatures (Tdep) between 110 and 450 degrees C, are presented and discussed. Anomalously high optical absorption was observed for films prepared at a floating potential, which is a few orders of magnitude higher than of single-crystal Si for samples prepared at Tdepbetween 260 and 350 degrees C and, in the photon energy range up to 2.0 eV, is also higher than that of amorphous Si. Samples prepared at a floating potential at Tdep<or approximately=180 degrees C and >or approximately=400 degrees C, and those prepared at a negative substrate bias, show a lower optical absorption, which for the latter films is similar to that of amorphous silicon. Annealing up to 800 degrees C under ultra-high vacuum resulted in a small but reproducible increase in absorption independent of Tdep. Similar annealing experiments followed by absorption measurements in high vacuum indicated no measurable effect of the adsorbed oxygen on the optical absorption. The angular dependence of the forward light scattering from the films was measured at various wavelengths and found to diffuse scattering and absorption in the films. Furthermore, quantitative estimates of the surface roughness of the films from reflection data and scanning electron micrographs were made, and these results are discussed with respect to the enhanced absorption and scattering in the films.

Reliability of high vacuum measurements

In order to allow the users of vacuum measurements to assess the reliability of their measurements, the current state of high-vacuum standards and gauging is reviewed. The discussion includes several types of high-vacuum primary standards currently in use, an assessment of probable errors for several types of hot filament ion gauges, user-controlled factors that may serve to increase the errors, and the information available to date on the performance of a commercially available molecular drag gauge. Examples are given of the introduction of additional errors by the improper application of vacuum gauges.

Measurement of high vacuum

A new logarithmic unit of vacuum is proposed to replace the torr or mmHg, with distinct advantages to workers in the electron tube industry and in vacuum physics.

The quadrupole and its applications in vacuum technology and mass spectrometry

The quadrupole mass spectrometer has gained in recent years much popularity due to favourable characteristics, such as high sensitivity, fast mass scan, small size and especially ease of operation. The principles of operation are discussed briefly. Some of the applications in chemistry and physics and in Vacuum technology in particular discussed are: partial pressure measurement and leak detection in high Vacuum and ultra high vacuum systems; thin film and electronic components production control; pressure standards testing; and automatic process control.

The measurement of total pressure in the range 10 −8 to 10 −12 torr

This short review paper is intended to act as a general introduction to the papers presented at the one day meeting on the subject of measurement of total pressure in vacuum systems. Because of the great scientific interest in measurement in ultra high vacuum (UHV) the paper concentrates entirely on this aspect of the subject. Various techniques that have been introduced to extend the working range of ionization gauges below 10−9 or 10−10 torr will be described briefly. Included will be the modifications made to the Bayard Alpert gauges to suppress both surface ion and X ray induced currents. Also discussed will be the magnetron and orbitron gauges in which sensitivity is greatly increased by forcing the electrons to execute very long oscillatory paths in the ionization chamber. The cold cathode Penning gauge will be mentioned.

An external collector gauge for ultra high vacuum measurement

A brief review of developments designed to reduce the low pressure measurement limit of hot cathode ionization gauges is given. The two main considerations when reducing the low pressure limit are residual current and sensitivity. An external collector gauge has a low residual current due to the ion collector being placed outside the grid volume. The evaluation of a gauge of this type is described. An increase in sensitivity obtained without an increase in residual current also has the effect of reducing the low pressure limit. It is shown that an improvement in sensitivity can be obtained by ensuring that the ratio of radial to tangential energy of electrons entering the grid is as high as possible.

Measurement of Extreme High Vacuum by Negative Potential Modulation Method with a Modulated Bayard-Alpert Gauge

Measurement of Extreme High Vacuum by Negative Potential Modulation Method with a Modulated Bayard-Alpert Gauge

1287. High vacuum measurement by means of virtual cathode relaxation time: O Lloyd,Brit J Appl Phys,17(3), Mar 1966, 357–370

1287. High vacuum measurement by means of virtual cathode relaxation time: O Lloyd,Brit J Appl Phys,17(3), Mar 1966, 357–370

High vacuum measurement by means of virtual cathode relaxation time

The theory of virtual cathode formation in electron beams is reviewed. Destruction of a virtual cathode by the accumulation of residual gas ions is shown to occur in a time which is inversely proportional to the pressure. This forms the basis of a method of measuring low pressures which may have some advantages over conventional ionization gauges, especially in the presence of high magnetic fields. Experimental results are presented where this effect is used to measure pressures in the range 10-4-4 ? 10-9 torr.

16. High-vacuum measurements and an improved calibration system: Anon,Varian Publications, California, USA, 1964

16. High-vacuum measurements and an improved calibration system: Anon,Varian Publications, California, USA, 1964

Adsorption measurements in high vacuum: (Roumania)A Cavaleru et al, Rev Roum Phys, 9 (2), 1964, 127–128

Adsorption measurements in high vacuum: (Roumania)A Cavaleru et al, Rev Roum Phys, 9 (2), 1964, 127–128

Adsorption measurements in high vacuum

After a brief review of the methods employed in studies of ionically induced adsorption of gases in high vacuum, a measuring method is presented which permits the study of the different sorption phenomena in successive steps. The experiments are described by quite simple equations since the pressure during the pumping period is kept constant; a maximum amount of information is extracted from the recovery curves.

THEORY OF KLUMB-SCHWARZ TYPE RADIOMETER GAUGE

摘要 Klumb-schwarz提出的同轴圆筒形辐射真空计,原则上可以作为低气压的绝对量具,然而由于迄今并未有人提出完整的灵敏度理论,困此限制了它作为绝对量具的可能性。本文叙述一种近似解法,可以得出灵敏度的绝对值,并从理论上决定其最佳几何结构。最后还对这种真空计的量程上下限作了讨论。 Abstract Klumb-Schwarz type radiometer gauge (Knudsen gauge) is an absolute gauge for high vacuum measurements, but since its theoretical sensitivity is so far unknown, in practice it needs calibration against another absolute gauge (e. g. McLeod). In this paper a simple theory to determine the sensitivity of a Klumb-Schwarz gauge is described. The optimum angle of the vane is decided as 24° by theoretical considerations. It is further shown that in this gauge the force due to electromagnetic radiations limits the lower range and is something in analogue with the soft X-ray effect in conventional hot-cathode ionization gauges. 作者及机构信息 李志岩, 黄慕贤, 潘震明 Authors and contacts LEE Z. Y., WANG M. Y., PAN Q. M. 参考文献 [1] 施引文献

Measurements and Collision—Radiation Damage Theory of High-Vacuum Sputtering

A brief summary of some of the important experimental and theoretical work related to the subject of metallic sputtering is presented. The need for measurements in high vacuum is indicated and an ion beam which utilized a Philips Ion Gauge discharge ion source to make high-vacuum sputtering ratio measurements is described. Absolute sputtering ratio data for the gas-metal combinations Ag-Kr, Ag-A, Ag-Ne, Ag-He, Cu-Kr, Cu-A, Pb-A, and Pb-He are presented in terms of the number of atoms sputtered per incident ion, ${n}_{a}$, versus incident ion energy, ${E}_{0}$, for ion energies varying between 400-6100 ev. The data are interpreted by treating the incident ion as a hard sphere which "cools" in a manner similar to a neutron losing energy by collisions in a lattice, each collision producing recoil atoms and atomic displacements near the surface. The number of atoms escaping, or "sputtering," from the metallic surface is reduced from the number displaced by absorption within the metal which is accounted for by a parameter $\ensuremath{\alpha}$. By use of elementary neutron cooling theory and the Seitz formula for displacements produced by a recoil atom within a solid, the formula for the number of atoms sputtered per incident ion is given by ${n}_{a}={\left(\frac{\ensuremath{\epsilon}{E}_{0}}{{E}_{d}}\right)}^{\frac{1}{2}}\ensuremath{\Sigma}\stackrel{{n}_{c}}{n=1}{e}^{\ensuremath{-}\ensuremath{\alpha}\ensuremath{\surd}n}{e}^{\ensuremath{-}\frac{(n\ensuremath{-}1)\ensuremath{\xi}}{2}}, {n}_{c}=\frac{1}{\ensuremath{\xi}}\mathrm{ln}\left(\frac{\ensuremath{\epsilon}{E}_{0}}{{E}_{d}}\right),$ for the case of ions more massive than the metallic atoms. The effect of ions rebounding from the surface after the first collision is considered to produce effectively two types of incident current particles; (1) incident gas ions and (2) recoil metal atoms. These considerations lead to a modified sputtering ratio formula, which reduces to the above equation when ${M}_{1}\ensuremath{\geqq}{M}_{2}$. The displacement energy for the process, ${E}_{d}$, is calculated by use of G. K. Wehner's data on sputtering thresholds and the relation ${E}_{t}=\frac{{E}_{d}}{\ensuremath{\epsilon}}$. A fair fit to the experimental data is obtained by suitable choice of $\ensuremath{\alpha}$ in the modified formula for the cases studied.The use of "hard" collisions is justified and an equivalent ion energy shift defined by equal average energy transfer on the first ion-atom collision is applied to the data. The subject of sputtering thresholds is treated by an attempt to bracket observed thresholds, ${E}_{t}$, between limits defined by the atomic heat of vaporization, the displacement energy, and the average energy transfer per collision.

Measurement of high vacuum at low temperatures

Measurement of high vacuum at low temperatures

Apparatus for the measurement of ionic conductance of solid salts

An apparatus designed to measure the specific ionic conductance of solid salts in the range 10-9 to 10-13 Ω-1 cm-1 is described. The use of a low-frequency pulse technique to avoid polarization together with the precaution of making all measurements in high vacuum, have enabled values of κ as low as 5 × 10-15 Ω-1 cm-1 to be determined. The performance of the apparatus is illustrated by the results obtained in the determination of the specific conductance of potassium and strontium azides.

Recent advances in the production and measurement of high vacua

Recent advances in the production and measurement of high vacua

The construction and calibration of a sensitive form of Pirani gauge for the measurement of high vacua

The low-pressure gauge here described consists of a manometer and a compensator of identical construction placed in the opposite arms of a Callendar-Griffiths bridge. Each comprises, essentially, a loop of 10 cm. of platinum wire, 0.001 in. in diameter, together with a compensating loop of 2 cm. of the same wire. The symmetry of the circuit makes errors due to thermo-electric effects very small. Investigations have been carried out to ascertain how the sensitivity of the instrument depends upon (1) the diameter of the gauge; (2) the temperature of the wire; (3) the temperature of the external walls; (4) the nature of the material of the external walls. The gauge follows variations of pressure with considerable rapidity, and its range of measurement is from 2 × 10-3 mm. to 4 × 10-6 mm. approximately.