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News Briefs
November 1961 Radio-Electronics

November 1961 Radio-Electronics

November 1961 Radio-Electronics Cover - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Electronics, published 1930-1988. All copyrights hereby acknowledged.

sink-me

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News Briefs

Diamond Semiconductors Made

Dr. Guy Suits of the General Elec-tric Research Laboratory has announced the discovery of methods for producing semiconducting diamonds. Such gems are very rare in nature - less than 1% of all natural diamonds, but now can be grown at will in the laboratory. Semiconducting borazon (a form of boron" nitride with a structure like that of diamond and equally hard) has also been made at the laboratory.

The method for making semiconducting diamonds was discovered by Dr. Robert H. Wentorf, Jr., of the Research Laboratory, and Harold P. Bovenkerk, of G-E's Metallurgical Products Dept. Semiconducting borazon was discovered by Dr. Wentorf, who also developed the original process for making borazon. Diamonds are made semiconducting by adding impurities such as boron, beryllium or aluminum to the mixture of graphite and catalyst from which diamonds are made. The mixture is subjected to pressures of about 1,000,000 pounds per square inch and temperatures above 2000°F. Under these conditions, diamonds form with concentrations of 1% or less of the desired impurity, and have electrical conductivities in the semiconducting range (intermediate between those of metals and insulators).

Drs. Wentorf and Peter Cannon of the Research Laboratory have also prepared semiconducting diamonds by diffusing boron and aluminum into man-made or natural diamonds at high pressures and temperatures. All the semiconducting diamonds made so far have been p-type (positive current carriers). Both p-type and n (negative current carrier)-type crystals are necessary in transistors and other semiconducting de-vices, and a search for processes that will produce n-type diamonds is continuing.

Tests on such junctions have shown that they act as rectifiers (allow current to flow in only one direction). Beryllium as an impurity produces p-type borazon, and a number of substances including sulfur, silicon, many organic compounds, and potassium cyanide, when added to the synthesis mixture, result in n-type borazon.

The semiconducting diamonds prepared with boron are blue, in shades ranging from a pale blue-white to a deep blue-black, depending on how much boron is present in the crystal. Semiconducting diamonds found in nature, which have been studied for many years by a number of investigators, are also sometimes blue. One of the most famous blue-white diamonds is the Hope diamond, and although its conductivity has not been measured up to the present time, its color suggests that it is probably a semiconductor.

Test setup for checking electrical characteristics of semi-conducting diamonds. Diamond is held in place by 5 contact pins.

Nuclear TV Coming?

A TV satellite with a nuclear power plant was proposed at a Congressional hearing by Commissioner Robert E. Wilson of the Joint Committee on Atomic Energy. Wilson stated that a nuclear-powered satellite with a 1-kw TV transmitter could be developed in 2 to 3 years. Enough power for hemisphere coverage would need about 15.0 kw, however, and though not so easy to realize, would be possible in this decade. "In my opinion," stated Commissioner Wilson, "this would mean a great deal more to the aver-age individual than a manned landing on the moon."

NBS Revalues Its Ohm

The National Bureau of Standards has redetermined its primary unit of electrical resistance by a new, more accurate method. The new evaluation was made by using a 1-picofarad capacitor, capacitance of which was determined to a very high degree of accuracy from its mechanical dimensions. The NBS unit of resistance is found to measure 1.000002 ohms.

The method of measurement was to build a capacitor of such a type that its capacitance could be determined very accurately. The one developed by the bureau is constructed of gauge blocks. The impedance of the capacitor at an accurately determined frequency is compared with that of the reference resistors. Besides being more accurate, the method is simpler and faster than previous methods, both in making the measurements and in the construction of the equipment required.

 

 

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