Low-Temperature Properties of Evaporated Lead Films
01 Nov 1963-Journal of Applied Physics (American Institute of Physics)-Vol. 34, Iss: 11, pp 3261-3266
TL;DR: In this article, the residual mechanical stresses present in lead films have been determined as a function of film thickness and film purity, and the experimental values for the stress were found to be appreciably larger than values calculated on the basis of bulk data.
Abstract: Lead films have been deposited onto room‐temperature substrates having low thermal expansion coefficients and the residual mechanical stresses present in these films have been determined as a function of film thickness and film purity. At room temperature no measurable stress (<5×107 dyn/cm2) was present in any film. At 78° and 4.2°K the stress σ was given by σ=α+β/d, where α is a constant dependent on temperature and d is the film thickness. A model involving surface pinning of dislocations predicts an equation of this form, but the experimental values for the stress were found to be appreciably larger than values calculated on the basis of bulk data. The experimental values were substantiated by superconducting critical temperature measurements on films of various thicknesses. Localized crystalline growth was observed in lead films after cooling to 4°K. The film material around these micron‐size crystals exhibiting five‐ and sixfold rotational symmetry was thinned to the point that physical holes were e...
Citations
More filters
TL;DR: In this paper, the stresses that develop in thin films on substrates can be detrimental to the reliability of thin film electronic devices, in order to design these devices for improved mechanical reliability, an...
Abstract: The stresses that develop in thin films on substrates can be detrimental to the reliability of thin film electronic devices. In order to design these devices for improved mechanical reliability, an...
560 citations
TL;DR: In this article, the authors showed that the hillock formation observed in the present case has been explained on the basis of thermal stress relaxation occuring by diffusion creep, with the additional effect of the high surface diffusion of silver atoms on an oxygen-covered silver surface.
187 citations
TL;DR: A model for hillock growth in thin films such as those of lead and tin is developed in this article, where the authors take into account Nabarro Herring diffusion creep as a parallel stress relaxation mechanism and the effects of film thickness on hillock density.
Abstract: A model for hillock growth in thin films such as those of lead and tin is developed. It is proposed that hillock growth is a form of stress relaxation in which atomic species diffuse along the film‐substrate interface to the base of the hillock. The latter extrudes out along the grain boundaries connecting it to the rest of the film. The stability and kinetics of this process are considered. Taking into account Nabarro‐Herring diffusion creep as a parallel stress relaxation mechanism observations such as an incubation period for hillock growth and the effects of film thickness on hillock density are accounted for. In addition, observations on lateral growth of hillocks and unusually tall hillocks (whiskers) are interpreted within the framework of the present model.
182 citations
TL;DR: In this paper, a new technique for fabricating Josephson tunneling barriers has been developed, which includes an rf sputter etching step in argon for cleaning, followed by an Rf sputtering step in oxygen, which is attributed to a balance between sputtering and oxidation rates.
Abstract: A new technique for fabricating Josephson tunneling barriers has been developed. Oxide tunnel barriers with estimated thicknesses from 20 to 50 A have been formed on lead films with indium underlayers and on niobium films. The technique includes an rf sputter etching step in argon for cleaning followed by an rf sputter etching step in oxygen. During the latter, an oxide film is grown having a steady‐state thickness which is attributed to a balance between sputtering and oxidation rates. Different oxide thickness may be obtained by varying process parameters such as oxygen pressure and rf power.
141 citations
TL;DR: In this article, the authors describe hillock growth as proceeding by surface diffusion to reduce compressive stresses caused by differential thermal expansion between film and substrate, and the effects of oxygen atmospheres are accounted for in terms of the energetics of hillock nucleation.
93 citations
References
More filters
555 citations
TL;DR: In this article, the authors compared the stress-strain behavior of evaporated gold films with that of whiskers and found that the former owe their high strength to a high concentration of defects which were uniformly quenched in during the evaporation process, and which greatly impede dislocation motion and multiplication.
Abstract: Evaporated gold films in the 500–15 000 A thickness range were prepared on rocksalt substrates. Depending on the temperature of the substrate during deposition, the films were completely, partially, or randomly oriented with respect to the (100) plane of the rocksalt, as determined by x‐ray diffraction. The stress‐strain curve of the free films was investigated and was found to be quite steep up to very high stresses, but plastic deformation and creep were observed even at relatively low stresses. The ultimate tensile strength of the films is from 2 to 4 times that of the annealed bulk material and is not a function of film thickness. The Young's moduli are found to be normal. Comparing the stress‐strain behavior of evaporated films with that of whiskers suggests that the former owe their high strength to a high concentration of defects which were uniformly quenched in during the evaporation process, and which greatly impede dislocation motion and multiplication, and not to an abnormally high stress requi...
109 citations
TL;DR: In this paper, the adiabatic elastic moduli of lead have been measured from 4.2° to 300°K using the ultrasonic pulse echo method, and a Debye θn of 105.3° K was obtained.
Abstract: The adiabatic elastic moduli of lead have been measured from 4.2° to 300°K using the ultrasonic pulse echo method. The Debye θn obtained from the 4.2° K modulus values is 105.3° K and is to be compared with the θn of 108° K obtained from specified heat measurements.
101 citations
01 Nov 1953
TL;DR: In this paper, the authors made measurements of the stress in deposits of Ni, Fe, Pd, Au, Cu, Ag, Sb, Al, Bi, Mg and Zn.
Abstract: Measurements are made of the stress in deposits of Ni, Fe, Pd, Au, Cu, Ag, Sb, Al, Bi, Mg and Zn condensed from the vapour in high vacuum on copper strips used as substrates. The stress is found to be characteristically of a tensile nature and the amount of stress is different for different metals. The occurrence, nature and order of magnitude of the stress are explained as arising from the contraction of the upper regions of the growing deposit as they cool after their deposition, which takes place at a temperature generally several hundred degrees higher than the initial substrate temperature. According to this interpretation, this contraction will begin to set up a tensile stress in any stratum of the deposit as soon as the temperature of the region concerned falls below the recrystallization temperature of the deposit metal. An estimation of the stress to be expected from this cause falls in the region of the experimentally determined values. In Al a compressive stress is observed if the metal is evaporated in an imperfect vacuum, the air pressure being about 10-4 mm Hg or higher. Evidently appreciable oxidation of the aluminium occurs and the compressive stress is associated with the formation of the oxide between the metal crystals or included to some extent within the crystals. Results for electrodeposits are analogous.
90 citations
TL;DR: In this paper, a small hole was drilled through the substrate with a water jet, and the mechanical properties were determined by stressing the unsupported film over this hole, which was observed to undergo considerable plastic deformation, accompanied by the appearance and growth of mechanical twin bands as the stress was increased.
Abstract: Single‐crystal gold films were grown by vacuum deposition on heated (375°C) sodium chloride substrate blanks. Completely oriented films with thicknesses between 1000 and 3000 A were obtained, with the plane of the film being the {100} crystallographic plane. A small hole was drilled through the substrate with a water jet, and the mechanical properties were determined by stressing the unsupported film over this hole. The films were observed to undergo considerable plastic deformation, accompanied by the appearance and growth of mechanical twin bands as the stress was increased. X‐ray diffraction studies were made to determine the twin orientation. Both the ultimate tensile stress and the elastic modulus were found to increase as the thickness of the films was reduced.
72 citations