The temperature coetlicients of resistance (TCR) of films of sputtered Au, Ir, Mo, Ni, Pd, Pt, Rh, Ta, and W, of evaporated AI, Cr, Ti, and Zr, and of the alloy films Pt-Au, Pt-Ir, and Pt-Ni have been measured in vacuo over the temperature range 25° to 600°C; the film thickness range was 75 to 2oooA. The TCR values of films of the substantially pure metals were in the range i to i those of the respective bulk metals whether deposited on glass, Vycor, or Stupalith substrates. The departure of the conditions of growth of the film from those usual for the bulk metal, i.e., rapid cooling effects and impurities present, contributed imperfections which reduced the TCR of the film. The TCR values of alloy films were low, 0.0004 per °C for Au-Pt, and resistivities were 3 to 4 times that of either constituent. The TCR values of sputtered films of Mo, W, and Ta and of evaporated Cr, Zr, and Ti were generally less than 0.0001 per °C. Electron diffraction examination of films of these latter metals revealed oxide inclusions in the films. The presence of the oxide of the metal reduced the TCR and increased the R/sq of the film as compared to those of the pure metal. Only films of gold, platinum, and iridium were corrosion resistant in air near 600°C. Overcoats of evaporated SiO provided partial protection for the others. Powers up to 15 watts were dissipated by refractory metal films only i2 by ! in. and about 750 A thick. These high values contrasted with less than l w for a gold film of similar dimensions.*
Articles you may be interested inMethod and a simple apparatus for rapid simultaneous measurement of resonance frequency and Q factor of a quartz crystal Rev.
Studies of the alloying of thin bimetal films of 20 metal pairs have been conducted by measurement of changes in the properties of the films before and after heating to successively higher temperatures in vacuo. Films consisted of layers of about 1000 angstroms of each metal consecutively deposited or of a single layer of 2000 angstroms formed of two metals deposited simultaneously. Techniques of study included visual examination of color changes, measurements of changes in electrical resistivity and temperature coefficient of resistance, metallography, x-ray diffraction, electron microscopy and diffraction, and measurement of frequency changes of piezoelectric resonators coated with a metal pair. Regardless of the method of coating, i.e., evaporation, sputtering, or electroplating, films were found to interdiffuse or alloy at or below the temperature of recrystallization of the metal of higher melting point. The order of deposition of the films affected their subsequent behavior. Films of aluminum formed an oxide coating during a few minutes storage in vacuo; the oxide appreciably retarded diffusion between the layers until a temperature of about 400°C was reached. Simultaneous evaporation produced films which alloyed readily at relatively low temperatures or, in the absence of intrinsic alloying affinities of the metal pair, films of highly imperfect structure. The imperfection of the latter was exhibited by reductions of up to 90% in the electrical resistance of the films upon annealing. By the methods outlined valuable studies of the properties of metals can be conducted with microquantities of the metals at temperatures below 0.40°Km (melting point °K); and alloys unavailable commercially can be prepared in the laboratory at minimum expense.
In the past, soldering to thin metal films on glass or quartz substrates has normally been accomplished by suitably reinforcing the film at the soldering point with a thicker underlying film. This performance is necessary in order to prevent tin-lead solders and commonly used fluxes from destroying the film and to give better adhesion to the substrate. It has been found that by using the metal indium and certain of its alloys as a solder, without a flux, adherence to thin metal films may be readily obtained without destruction of the film. Since indium also adheres to glass, quartz, ceramics, and silicious minerals, the strength of the joint is not determined by the strength or adherence of the metal film but by the strength of the indium-glass or indium-quartz bond. Thus, films of only a few angstroms in thickness may be soldered without damage, with good mechanical strength and electrical contact. The strength of the bond is usually about 500 pounds per square inch. This technique has been found most useful in studying the resistivities of thin metal films and in the mounting of metal-coated piezoelectric crystals. Soldered connections have been made to films of 18 metals including aluminum, titanium, and zirconium.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.