摘要:

An electron spectrometer has been constructed, which is capable of detecting the vibrational states of gases adsorbed on solid surfaces. It has been found that the excitation of fundamental, harmonic, and combination frequencies can be detected with this instrument. The vibrational spectra due to the adsorption ofH2,N2, CO, andH2Oon the (100) surface of tungsten have been observed. A number of conclusions concerning the adsorbed state of these gases can be drawn from these spectra. These spectra and conclusions are presented and discussed. A brief description of the apparatus is also included.

ISSN:0022-5355    

DOI:10.1116/1.1492522

出版商:American Vacuum Society    

年代:1967

数据来源: AIP

摘要:

Modulation of the ion current in Bayard-Alpert gauges allows operation at pressures below the normal x-ray limit and the measurement of pressures of electronically desorbable gases (e.g.,O2, CO, andCl2). Modulation by the method originally proposed (mode I) has two undesirable features: (a) modulation may cause pressure bursts, and (b) some modulation of the x-ray photocurrent occurs. Various alternate modulation methods are examined to determine which method minimizes the undesirable effects. A modulator external to the grid is only effective with electron currents less than 5 mA and with an open end grid. Two methods using a modulator internal to the grid are shown to be satisfactory; in the first (mode II), proposed by Lange and Singleton, the ends of the grid are left open and the modulator is switched from grid potential(Vg)to about(Vg− 20)V. In the second (mode III) the ends of the grid are cloud and the modulator is switched from(Vg− 20)to(Vg− 60)V.

ISSN:0022-5355    

DOI:10.1116/1.1492523

出版商:American Vacuum Society    

年代:1967

数据来源: AIP

摘要:

Recent work has provided better understanding of orbitron gauge performance and has led to substantial improvements. Coupling between the filament and the central field is a major factor controlling linearity, sensitivity, and oscillations. Positive ion emission from the filament, excess energy electrons reaching the ion collector and x-ray photocurrent are factors which can cause errors at low pressure. The present design is very simple with little structure inside the gauge to perturb pressure measurements. Gauge sensitivity has been increased by a factor of four, so only a 1-μA electron current is now required to produce the same ion current obtained from an 8-mA emission in the Bayard-Alpert gauge. Total power input to the gauge is less than 100 mW. The ion current is approximately linear with pressure from10−11−10−5Torr. The linear region can be extended to10−2Torr by operation in a non-orbiting mode.

ISSN:0022-5355    

DOI:10.1116/1.1492524

出版商:American Vacuum Society    

年代:1967

数据来源: AIP

摘要:

This paper gives a survey of materials suitable for the preparation of dielectric films for interference coatings, highly reflecting metallic films, and semitransparent coatings for neutral density filters and sunglasses. It is shown that improved vacuum-deposition techniques and treatments, such as evaporation by electron bombardment, film deposition under ultrahigh vacuum conditions and at extremely high rates, reactive evaporation in an oxygen atmosphere, and ultraviolet irradiation after the film deposition, have greatly increased the number and improved the quality of film materials for optical applications. The most important factors for producing dielectric films with high transmittance and metallic coatings with high reflectance are discussed. Coatings suitable for controlling the temperature of satellites and space vehicles are described.

ISSN:0022-5355    

DOI:10.1116/1.1492525

出版商:American Vacuum Society    

年代:1967

数据来源: AIP

摘要:

Sputtered β-tantalum thin films were produced in a two-chamber vacuum system (entrance chamber and sputtering chamber) with typical background pressure of1×10−7Torr. Both the resistivity and sheet-resistance uniformity were almost entirely dependent on cathode voltage; a sheet resistance uniformity of ±1% over a 3 in. by 4 in. substrate was achieved. The application of negative-anode bias voltage was found to control β-tantalum film resistivity; a 53% reduction in resistivity was caused by a −200-V anode bias voltage applied during a 4-kV cathode sputtering run. A relationship between resistivity and plasma potential was found, which unifies both cathode voltage and anode-bias voltage effects. The electrostatic environment of the substrate appears to control the resulting β-tantalum film properties. Continuous sputtering over a period of several days was required to initially achieve equilibrium conditions in the sputtering chamber. The application of direct-substrate negative bias voltage during cleanup reduced the β-tantalum resistivity and, in some cases, produced a mixed structure of both bcc and β tantalum.

ISSN:0022-5355    

DOI:10.1116/1.1492526

出版商:American Vacuum Society    

年代:1967

数据来源: AIP

摘要:

The composition of the ambient atmosphere during the sputtering of tantalum films in argon glow discharges has been studied by means of a mass spectrometer adapted both for residual analysis of vacua between10−9−10−5Torr, and process monitoring at pressures of(10−50)×10−5Torr. The partial pressures of a number of residuals were found to increase immediately upon initiation of the discharge in both an oil diffusion and a turbomolecular pump system. The total background gas levels during the discharge were in the1×10−5−5×10−4Torr range, with the major component being hydrogen, and smaller contributions from water vapor and methane. The pressure increase of these species resulted from ion bombardment decomposition of adsorbed surface layers, and exhibited two maxima. The first is attributed to desorption from the electrodes, and the second to desorption from the bell jar wall.The spectrometer was used for detailed studies of the gettering of deliberate additions ofN2,CH4andH2during sputtering in argon. Considerable differences were found in the effect of the glow discharge on those gases, with the gettering ofCH4andH2exhibiting a complex time dependence. Tantalum films sputtered without deliberate gas additions, were found to be of the beta-tantalum form even when the discharge-generated background was reduced to∼1×10−6Torr by long presputtering.

ISSN:0022-5355    

DOI:10.1116/1.1492527

出版商:American Vacuum Society    

年代:1967

数据来源: AIP

摘要:

The critical-field theory of electrical breakdown in vacuum is shown to be applicable to all of the twelve metals and to the one alloy tested. In this theory the electric field at breakdown is predicted to be independent of gap spacing when the field considered is that existing in the neighborhood of cathode field-emission sites. This field is enhanced with respect to the average gap field by a factor which can be calculated from measurements of the field-emission current prior to breakdown. A vacuum tube has been employed for the experiment in which one electrode is movable and in which foils may be used for the electrode materials. The critical field for breakdown compares well with that calculated by others in the four metals for which previous data exist.

ISSN:0022-5355    

DOI:10.1116/1.1492528

出版商:American Vacuum Society    

年代:1967

数据来源: AIP

ISSN:0022-5355    

DOI:10.1116/1.1492529

出版商:American Vacuum Society    

年代:1967

数据来源: AIP