Cryogenic, three-terminal device yields current-voltage characteristics of ordinary transistor. Device consists of two superconducting tin rods in a crossed-wire geometry, separated by a thin gold film. New construction technique is described and possible applications are discussed

Meissner, H.

English

NASA Technical Reports Server

I 
Holder and Electrical 
Contact to Gold Film 
Tin Wire	 Tin Wire
Perspective View of a Superconducting Transistor 
A new effect has been observed in the laboratory, 
A cryogenic, three-terminal device has yielded cur-
rent-voltage characteristics similar to those of an 
ordinary transistor. The device was made from two 
superconducting tin rods in a crossed-wire geometry, 
separated by an 1860 A-thick single crystal of non-
superconducting gold. 
Anew technique for constructing 'the device has 
been used. The three elements are pressed together 
by externally controlled mechanical pressure, only 
after they have been cooled to cryogenic temperatures. 
Major advantages of this technique over those which 
involve grown junctions are that no intermetallic dif -
fusion occurs at the junction, and that separate prep-
aration of the three elements, in order to produce 
clean surfaces and accurately known film thicknesses, 
is much easier. A much longer electronic mean free 
path is thus obtained and undesirable effects caused 
by wide, inhomogeneous transition zones between the 
different metilclimin eliminated
December 1970	 Brief 70-10082 
fl
NASA TECH BRIEF 
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application. Tech Briefs are available on a subscription basis from the National Technical Information Service, Springfield, 
Virginia 22151. Requests for individual copies or questions relating to the Tech Brief progam may be directed to the Tech-
nology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Superconducting "Transistor" Acts as High-Speed Switch 
The gold film used in the device is grown separately, 
by vapor deposition on a highly polished crystal of 
sodium chloride, which is subsequently dissolved 
in distilled water. The film is supported on a small 
loop of copper wire, lifted from the water, 1Ins,.., 
and dried. The two tin rods are electropolished to 
remove dirt and oxides, and to provide as smooth a 
surface as possible. Leads are then connected to the 
three elements (contact to the gold film is made 
through the copper loop). The two tin rods are 
mounted in special holders, with one rod fixed and the 
other clamped to a spring-loaded mechanism which is 
remotely adjustable, and which is initially set so that 
the two tin rods are separated. The gold film is 
mounted on a remotely adjustable, spring-loaded jack 
screw and suspended over the fixed rod. The whole 
assembly is mounted in acryostat, which is evacuated 
and cooled to 4.2°K by liquid helium. Then the 
springs are released, forming the electrical contacts 
between the gold film and the tin rods. 
The device, a perspective view of which is shown 
in the figure, is then cooled to a temperature of 
l.873°K, below the transition point of tin. The 
magnetic field in the vicinity of the device is reduced 
to less than 0.1 gauss by magnetic shielding. 
Current 11. corresponding to the emitter current 
of a normal transistor, is coupled from an external 
source into one tin rod, through the gold film, and out 
via the other rod. A second external source supplies 
current 12, corresponding to the base current of a 
normal transistor, to the gold film. 12 is also output 
through the second tin rod. Voltage V, corresponding
 
to the collector-to-emitter voltage of a normal transis- 
tor, is measured between the two rods. Current 1 is 
recorded as a function of V and 12, yielding the char- 
ANN, .	 ... .....	 acteristic transistor curves. 	 OLI 
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Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use Government nor any person acting on behalf of the United States	 will be free from privately ownedrights. 
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Notes: 
1. It should be observed that, at its current state of 
development, the superconducting transistor is a 
laboratory phenomenon only. However, further 
work may lead to the development of practical ap-
plications, including circuits which achieve extreme-
ly fast switching times. Such devices should be of 
considerable use in computer and microwave ap-
plications. 
2. Requests for further information may be directed 
to:
Technology Utilization Officer 
Headquarters 
National Aeronautics 
and Space Administration 
Washington, D.C. 20546 
Reference: TSP70- 10082
Patent status: 
No patent action is contemplated by NASA. 
Source: H. Meissnerof 
Stevens Institute of Technology 
under grant from 
NASA Headquarters 
(HQN- 10547) 
'I 
Brief 70-10082	 Category Ol


Superconducting ''transistor'' acts as high-speed switch

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