April 1960 Popular Electronics
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"A transistorized i.f.
stage for a TV set can be built today to fit into a match box. But molecular electronics has made possible the
production of a device that contains two such stages and is only a fraction of the size of a single transistor!"
Nobody talks of molecular electronics today, but that really is an accurate term for what we have when compound
semiconductors like GaAs, GaN, or any of the many-atomed exotic photovoltaic substrates are being discussed. When
referring to pure elements like silicon that are being doped with impurities, I'm not sure those structures are
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By J. K. Locke
a press conference in Washington recently, a demonstrator connected an ordinary phonograph to a pair of tiny
wafers that fitted easily into the palm of his hand. Then he hooked two leads from the wafers to a 15"
loudspeaker. When he flipped a switch, music filled the room.
The two little discs that did the man-sized
job of amplifying the weak signal from the record player into a hefty five watts of power are striking examples of
some of the first triumphs of "molecular electronics," a startling new design concept that promises to
revolutionize the entire electronics industry.
Molecular electronics is not just a new advance in
miniaturization. It is a radically different approach to electronic design that provides amplifiers, oscillators,
and other complete, operating electronic circuits without tubes, transistors, resistors, or capacitors.
Five full watts
of audio power can be obtained from the molecular electronic amplifier at left. In actual
use, the tiny unit is installed in a heat sink (black casing in lower photo). Smaller unit in demonstrator's hand
is a preamplifier. The amplifying system has an overall response from 0 to 20,000 cps. Comparison
of molecular electronic power converter with conventional circuit. In the molecular circuit, one block of material
does the entire job of rectification and filtering. Heat produced by passage of 110-volt alternating current
through the resistive domain (top layer) is transferred by the electrically insulating center layer to the bottom
layer, which is composed of a thermoelectric material.
A five-watt audio amplifier less than the size of a dime and a two-stage video amplifier much small still...
these are among the first products of an exciting new era, the age of Molecular Electronics.
Size reference of IC.
Multiple junction systems
attached to the dendritic ribbon above are complete multivibrator
circuits smaller than the point of a pencil. These are some of the first molecular electronic circuits to be
produced by entirely automatic machinery. Engineers hope that complete amplifiers, radios, and other more
complex circuits will soon be produced automatically.
greatly simplifies circuitry. A conventional transistorized circuit for a
light telemetry subsystem is shown in upper diagram above, with the equivalent molecular electronic circuit
below it. Fewer components and fewer soldered connections will increase reliability of equipment. Unit in photo
is the actual molecular electronic telemetry subsystem.
Although molecular electronics is hardly out of the laboratory, it is already clear that equipment using its
principles will be far smaller, lighter, more reliable, and ultimately cheaper than anything available today. One
example will illustrate its advantages.
A transistorized i.f. stage for a TV set can be built today to
fit into a match box. But molecular electronics has made possible the production of a device that contains two
such stages and is only a fraction of the size of a single transistor! . And the molecular electronic unit
operates on only a fraction of a volt - much less than the power required for transistors.
As far as
complexity is concerned, a transistorized circuit has perhaps a dozen components and 35 soldered connections,
while a comparable molecular electronic circuit only has about two parts and four connections.
The concept of molecular electronics was developed during the search for better
ways to miniaturize electronic equipment. While great strides had been made in designing smaller and smaller
individual components, it was obvious that far greater miniaturization and reliability could be achieved if all
the necessary electronic properties could somehow be built into a single, solid block of semiconductor material.
As solid-state physicists gained better understanding of the structure of materials and the flow of
electrical charges in them, it became possible to design simple "function blocks" containing, for example, both
capacitance and resistance. Later, n- and p-type materials were added to produce amplification as they do in
transistors and tunnel diodes. Finally, scientists were able to produce single bits of material that would
function as complete electronic circuits.
The various electrical properties such as resistance,
capacitance, and amplification are not localized in anyone spot in these function blocks. They are, instead,
distributed throughout the material. Molecular function blocks - even those as complex-looking as the five-watt
audio amplifier with its concentric rings - are not put together from a number of different parts. Instead, they
are cut from a single tiny chunk of semiconductor material. The block is then etched, alloyed and treated until
the desired results are obtained. Automatic Production.
Engineers are working on the
design of machines that will turn out completed circuits automatically. Although only the simplest circuits are
now produced by automatic machines, great strides have been made. For example, a method of drawing ribbons of
semiconductor material called "dendrites" directly from the molten mass has already been perfected. These ribbons
are of exact size and thickness, with optically perfect surfaces. They are practically ready for use as they
emerge from the furnace, and there are virtually no rejects.
By contrast, semiconductors are normally made
in the form of ingots which must be x-rayed, oriented, sawed, lapped, etched, and polished before they are ready
to use. In addition, this "old" method results in a high percentage of rejects.
A dendritic ribbon to
which tiny multiple-function systems have been automatically attached is. Here a series of multivibrators has been
created directly on the dendrite. The individual circuits need only be clipped apart and leads attached. Soon,
complete amplifier circuits will be produced the same way. The dendrite ribbon will be snipped into different
lengths to give amplifiers of different gains - the longer the strip, the greater the amplification!
Eventually, engineers hope to "grow" complex electronic equipment - complete receivers, for example -
automatically and continuously from a pool of semiconductor material. These receivers are still far in the future,
but they would be unbelievably cheap and trouble - free by today's standards. Because of the low power consumption
of molecular electronic function blocks, a single battery would last for years.
As might be expected, the first application for molecular electronics
will be in the military and space fields. The savings to be realized in weight, size, and power consumption are of
paramount importance here.
Of even greater significance is the tremendously improved reliability that can
be achieved through the use of these amazing devices. To see why, consider the example of a giant rocket designed
for hurling our satellites into orbit .
The rocket's electronic "innards" are made up of 20 or 30
thousand separate parts and perhaps 75 thousand connections. If just one of these parts or connections fails, we
suffer another missile failure. With molecular electronic equipment, only one-tenth to one-twentieth the number of
parts and connections is needed. Consequently, there is much less chance that a part or connection will go bad
under strain, and the promise is that missile firings will be far more successful than ever before.
Molecular electronic units for military use are now being developed by Westinghouse under a U.S. Air Force
contract. Although it takes time to design and test circuits, set up production lines, and train personnel, the
first of these units will be going into action within about three years. Consumer Use.
It is hard to say when molecular electronic products will be available for the consumer market. But it is a
certainty that such devices will be on sale some day. Because they will be produced by continuous, automatic,
low-cost production methods, their price is bound to become so low that conventional tube and transistor circuits
- with their separate resistors, capacitors, inductances, and complex soldered connections - will be on the way
out, except possibly for highly specialized uses.
Molecular electronic devices will open up exciting new
fields with their combination of high performance, small size, and low cost. For example, the wrist radio - a la
Dick Tracy - will become common-place. The personal telephone - a tiny gadget to strap on your wrist or carry in
your pocket - will become possible. With it, you will be able to call anybody in the world who is similarly
A flat-screen TV set that hangs on your wall like a picture will become a reality. Rapid
advances in electroluminescence have already come close to making practical a screen only a fraction of an inch
thick. Molecular electronics will make it possible to pack the rest of the TV circuitry into a hollow corner of
There are endless speculations possible on the changes molecular electronics will bring - the
probable developments in communications already mentioned are only a few. But who can say what revolutions in
medicine, industry, business, government, and other phases of human endeavor will come about?
As with most
truly revolutionary advances, molecular electronics will bring about profound changes impossible to predict. We'll
be looking forward to them eagerly, however. For certainly, molecular electronics, whatever its contributions,
will help shape a better and more exciting world for us all.