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

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Diffusion Pump Oil Deposition Measurements Utilizing Radioactive Tracers

J. G. Carter, J. A. Elder, R. D. Birkhoff, and A. K. Roecklein

J. Vac. Sci. Technol. 2, 59 (1965); http://dx.doi.org/10.1116/1.1492399 (4 pages) | Cited 1 time

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A radioactive tracer technique is proposed as a quick, simple, nondestructive method for measuring the deposition of diffusion pump oil and as a possible means of evaluating the efficiency of vacuum components. A simple bell jar vacuum system was assembled consisting of a 4-in. oil diffusion pump, a multicoolant baffle, a 4-in. gate valve, and a bell jar with associated gauges. Ten milliliters of Dow Corning 704 oil were irradiated in the low intensity test reactor at ORNL for 2.6 h. The ³⁰Si₁₄, comprising 0.54% by weight of the oil, becomes activated to ³¹Si₁₄. The system utilizing various baffle coolants, was operated for certain time intervals. The results indicate the presence of an initial backstreaming surge and also show the relative effectiveness of air-, water-, and liquid-nitrogen-cooled baffles. Deposition rates of a few Å∕h were measured.

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07.30.Cy

Vacuum pumps

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Angle-of-Incidence and Stress Effects on Rotating and Stationary Substrates

Klaus H. Behrndt

J. Vac. Sci. Technol. 2, 63 (1965); http://dx.doi.org/10.1116/1.1492400 (8 pages) | Cited 2 times

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Films deposited at an oblique angle-of-incidence of the vapor stream have frequently been observed to display an anisotropic structure because of preferential growth of the film material in the vapor direction. This phenomenon occurs on stationary substrates while, if the substrate is rotated during film fabrication, the vapor is deposited on all sides of a growing grain or island. If an integration is performed over the varying directions and amounts of the incident vapor, an “integrated incidence vector” can be calculated for planar substrates. Its direction should be that of average growth. It is calculated for which geometrical configuration (diameter and location of the substrate with respect to the source) this vector will be normal to the surface of the substrate, thus eliminating the angle-of-incidence effect. Then, the stress patterns in ZnS films on stationary and rotating substrates are discussed. It is shown that the pattern on stationary substrates is strongly affected by the angle-of-incidence while, on rotating substrates, no indication of incidence effects can be observed.

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81.15.Aa

Theory and models of film growth

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Adsorption–Desorption of Residual Gases in High Vacuum

David Lichtman

J. Vac. Sci. Technol. 2, 70 (1965); http://dx.doi.org/10.1116/1.1492401 (5 pages) | Cited 5 times

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Measurements have been made on the adsorption and desorption of residual gases in an ultra-high-vacuum ion-pumped system using mass spectrometer analysis. The predominant residual gases in our system are hydrogen, carbon monoxide, and water vapor at a total pressure of about 5×10⁻¹⁰ Torr. Mass analysis indicates two hydrogen peaks, one carbon monoxide peak, and no water vapor peak on thermally heating a molybdenum ribbon from room temperature to 1000 °C. Desorption and readsorption are observed continuously by monitoring ion desorption induced by an extremely low density (∼10⁻⁷A∕cm²) electron beam. Data obtained by this technique correlated very well with that obtained by thermal flashing and aids in understanding the reactions that are occurring. The use of electron-induced ion desorption coupled with mass analysis is seen to be a very useful tool in studying adsorption–desorption phenomena in high vacuum by allowing continuous observation as substrate conditions are changed.

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07.30.Bx	Degasification, residual gas
68.03.Fg	Evaporation and condensation of liquids
68.43.Mn	Adsorption kinetics

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Photodesorption of Carbon Monoxide

W. J. Lange

J. Vac. Sci. Technol. 2, 74 (1965); http://dx.doi.org/10.1116/1.1492402 (6 pages) | Cited 3 times

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The desorption of carbon monoxide from surfaces in a vacuum under photon irradiation has been studied. As the coverage on tungsten approaches completion, thermal desorption from a very weakly bound phase dominates. Negligible photodesorption from quartz is found. Desorption from borosilicate glass is found to be dependent upon the CO pressure and history.

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79.20.La	Photon- and electron-stimulated desorption
07.30.Bx	Degasification, residual gas

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Nucleation and Initial Growth of Single-Crystal Films

Robert F. Adamsky and Robert E. LeBlanc

J. Vac. Sci. Technol. 2, 79 (1965); http://dx.doi.org/10.1116/1.1492403 (5 pages) | Cited 12 times

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The mechanism of epitaxial growth has been investigated by the study of the nucleation process and early growth stages of single-crystal gold and silver films in (100) and (111) orientations. Films were grown by evaporation on vacuum-cleaved NaCl and mica cleavage planes, and on single-crystal NaCl films deposited on fresh mica cleavage surfaces. In the earliest observable period of growth, nuclei have been found to be as small as 5 Å in size. These nuclei, which contain 10–20 atoms, strongly indicate that growth proceeds continuously from initial nuclei consisting of only a few atoms. In subsequent stages of growth, coalescence processes occur which are governed by mobility of atoms and clusters on the substrate material. Mobility is highest on the evaporated film substrates, and leads to a decrease in nucleation density as a function of time because of rapid coalescence of the mobile nuclei. Nucleation rates have been measured as a function of substrate temperature and activation energies determined for the nucleation process.

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81.15.Aa

Theory and models of film growth

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Secondary Electron Emission of Vacuum-Cleaved Solids

N. R. Whetten

J. Vac. Sci. Technol. 2, 84 (1965); http://dx.doi.org/10.1116/1.1492404 (5 pages) | Cited 3 times

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Recent work on the secondary electron emission properties of solids with less than 1∕100 of a monolayer of adsorbed gas on the surface is reviewed. The solids were cleaved in a high vacuum so that secondary emission measurements could be completed in a time that was short compared to the monolayer adsorption time. The solids include graphite, NaCl, KCl, NaBr, KBr, and KI. The gases released from the alkali halides at the moment of cleavage were analyzed with a partial pressure analyzer.

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79.20.Hx

Electron impact: secondary emission