摘要:

Chromium and iron films of 10–50μm thickness were deposited on beryllium substrates by electron‐beam evaporation. Deposition rates varied from 35 to 425 Å/s. Substrate temperatures ranged from 300° to 650°C. The relationships between coatings characteristics and substrate temperatures, deposition rate, and angle of vapor incidence were studied. A columnar grain structure is achieved under these conditions with the chromium films having less than theoretical density. The chromium films become denser and less porous as substrate temperatures increases. The lack of full density in the chromium can be ascribed to discontinuities between grains. The iron coatings are denser, exhibiting very large columnar grains, approaching equi‐axed, at the higher substrate temperatures. Deposition rates above about 300 Å/s lead to splattering of the evaporant and conelike defects in the films. Vapor deposition at oblique angles leads to less dense coatings, with grain growth occurring radially toward the source. Coatings microstructures were not disturbed by multiple, interrupted deposition. Burnishing or sanding the chromium films tends to densify and crush the coating.

ISSN:0022-5355    

DOI:10.1116/1.569437

出版商:American Vacuum Society    

年代:1978

数据来源: AIP

摘要:

A selective solar photothermal absorber can be created by the formation of suitably spaced metallic dendrites. Spacings of around a micron achieve absorption of visible light through multiple internal reflections in a geometric maze effect while retaining the low emissivity properties of the metal at longer wavelengths. Recent experiments elsewhere on the chemical vapor deposition (CVD) of W dendrites on various substrates demonstrated the feasibility of this approach to produce a selective solar photothermal absorber. W dendrite coatings, however, may be too expensive to find a practical application in solar collectors. Ni dendrites, on the other hand, appear to be a potential low‐cost selective solar photothermal absorber. Dendrites are formed by the CVD of Ni from Ni carbonyl, Ni (CO)4. This paper presents the physical and optical results of experiments with CVD Ni dendrites on Al substrates. The preparation of the aluminum substrates, the CVD experimental apparatus and methods, and the optical measurement techniques of solar absorptivity (αs) and thermal infrared emissivity (ε) are discussed. The results are described in terms of scanning electron microscope (SEM) photographs of dendritic coatings, and the measured optical properties.

ISSN:0022-5355    

DOI:10.1116/1.569438

出版商:American Vacuum Society    

年代:1978

数据来源: AIP

摘要:

A range of metal silicide interference filters has been prepared on various metal substrates and aged in vacuum at elevated temperatures. These show promise as high‐temperature stable selective surfaces for solar energy phototheral conversion. Solar absorptances 75%–80% and emittances of about 2% can be obtained at room temperature for homogeneous metal silicide films on bulk copper. Higher absorptances are obtained using sputtered copper, bulk stainless steel, or evaporated nickel substrates. Emittances of homogeneous metal silicide films on bulk copper increase to about 5% at 500°C. The solar absorptance of an iron silicide on copper surface was temperature independent up to 500°C. Absorptances greater than 90% can be obtained for multilayer metal silicide films on copper. The emittances of these films are somewhat higher than for homogeneous films.

ISSN:0022-5355    

DOI:10.1116/1.569439

出版商:American Vacuum Society    

年代:1978

数据来源: AIP

摘要:

The principle of the plasma stream transport method is discussed and the transport characteristics are estimated. Using a simplified experimental machine based on this principle, transport experiments with silicon, silicon nitride, oxygen, and flurocarbon plasma stream were carried out. The deposition of silicon and silicon nitride films on silicon wafers was observed, and reactive etching of photoresist by oxygen and of silicon and silicon dioxide by fluorocarbon were observed.

ISSN:0022-5355    

DOI:10.1116/1.569440

出版商:American Vacuum Society    

年代:1978

数据来源: AIP

摘要:

Electron stimulated desorption (ESD) of adsorbed species from type 304 stainless steel (S.S.) was studied, primarily from the standpoint of controlled thermonuclear fusion reactor ’’first wall’’ applications. H+and F+were, by far, the most predominant ESD ion species observed from ’’as is’’ S.S. surfaces. O+, Cl+, and other ESD ions were also observed, but normally in much smaller quantities. The origin of the ESD ion signals are attributed to adsorbed H2and/or H2O for ESD of H+, and fluorocarbon and/or alkali halide contaminants in the case of ESD of F+. Little or no temperature effects on the H+and F+ESD ion signals were observed over the S.S. sample temperature range from 23° to ∠450°C. The total cross section for ESD of hydrogen was found to be ∠10−16cm2while that for ESD of fluorine was found to be ∠10−17cm2. The ion energy distributions of both H+and F+ions were obtained and no observable changes were found over the bombarding electron energy range 300–4000 eV. The total cross section for ESD of hydrogen from S.S. was investigated as a function of bombarding electron energy over the energy range 200–4000 eV. Relative cross sections for ESD of H+and F+were investigated over the bombarding electron energy range 50–6000 eV. The cross‐section behavior for ESD vs electron energy was found to be very similar to the behavior for electron–gas‐phase molecule interaction cross sections vs electron energy. The ESD cross‐section maximum was observed to occur at an electron energy of several hundred eV. Above this energy the cross section slowly decreased with increasing electron energy. The observed behavior of ESD cross section vs electron energy is attributed to the interaction of both primaryandsecondary electrons with the surface adsorbates.

ISSN:0022-5355    

DOI:10.1116/1.569441

出版商:American Vacuum Society    

年代:1978

数据来源: AIP

ISSN:0022-5355    

DOI:10.1116/1.569442

出版商:American Vacuum Society    

年代:1978

数据来源: AIP

摘要:

We describe a photoresist stencil technique that has proven to be quite reliable in the preparation of thin‐film Josephson logic and memory devices. The method employs multiple layers of resist with the top layer providing patterning and the bottom layer spacing the top layer from the substrate and providing an undercut under the top layer. This method has consistently produced uniform undercuts over ∠1 in. (∠2.54 cm) sample dimensions and has been used to produce micron‐sized patterns.

ISSN:0022-5355    

DOI:10.1116/1.569443

出版商:American Vacuum Society    

年代:1978

数据来源: AIP

摘要:

Hydrogen has been used at a pressure of 5×10−5Torr (6.6×10−3Pa) and at room temperature in an ’’ion‐etching beam mode’’ for cleaning solid surfaces. Two systems,viz. solvent‐cleaned and atmosphere‐exposed copper and heat‐resistant Fe–Cr–Ni steel, were analyzed in Auger spectroscopy before and after bombardment with hydrogen particles produced in a conventional ion gun. Copper is almost completely cleaned of carbon, sulfur, and oxygen within 30 min. A bulk‐carbon‐containing steel is completely freed from surface carbon while the bulk carbon is preserved in the subsurface zone at a satisfactory level. The proposed cleaning method seems to be very surface specific and nondestructive to subsurface layers.

ISSN:0022-5355    

DOI:10.1116/1.569444

出版商:American Vacuum Society    

年代:1978

数据来源: AIP

摘要:

The hydrogen and deuterium pumping speeds at ∠20 mTorr (2.66 Pa) and 300 K of 1000‐Å‐thick titanium films deposited at 300 K at a rate of ∠3 Å s−1have been measured. These speeds are approximately constant for H (or D)/Ti loading ratios between 0.3 and 1.3 and are different for each isotope. For deuterium the pumping speed is ∠0.13 l s−1 cm−2, while for hydrogen the speed is essentially two times the deuterium speed, i.e. ∠0.18 l s−1 cm−2. Pumping speed data taken at ∠5 mTorr (0.665 Pa) indicate that agreement of the isotope data with a surface‐sticking limited model requires a pressure‐dependent, hydrogen isotope‐independent sticking coefficient.

ISSN:0022-5355    

DOI:10.1116/1.569445

出版商:American Vacuum Society    

年代:1978

数据来源: AIP

摘要:

Characteristics of field electron emission from the dense array of microneedles of tungsten prepared on a 10‐μm tungsten filament were measured at an environmental pressure of ∠1×10−8Torr (1.33×10−6Pa). Electron emission was not uniform over the filament surface, but the variation of emission current with applied voltage explicitly obeyed the Fowler–Nordheim relationship. At an emission current of ∠10−4A, a vacuum arc was induced that led to a permanent change in current–voltage characteristic. Current fluctuation was dependent on emitter temperature and applied voltage, and the lowest fluctuation of about 4% was routinely obtained at ∠550 K and at applied voltages several percent lower than the arc‐inducing voltage. Macroscopic current density amounted to ∠20–80 mA/cm2at the best stability.

ISSN:0022-5355    

DOI:10.1116/1.569446

出版商:American Vacuum Society    

年代:1978

数据来源: AIP