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The Physical Sciences As the
Basis for Modem Technology
WILLIAM 0. BAKER
In some fields of the highest innovation and sophisticated tech-
nology, we are now seeing the elegant principles of twenizeth-ceraury
physical science being combined into operational systems for dra-
manc advances in economic and social functions. Since this tech-
nology involves every aspect of the wide reaches of physical science
gained during this century, we have a powerful answer to questions
of the practical values of research. Indeed, I submit that the physical
sciences have moved to a place where they will increasingly stim-
ulate not just originate but sizmz~late—large new fronners of tech-
nology anal engineering.
This discussion of the role of the physical sciences is enhanced by the
context that die editors of this volume have created. Science is skillfully
identified as to its human and institutional settings and its connections wad
government, academia, and industry in the chapter on science and technology
policy by Harvey Brooks. Likewise, Milton Katz's discussion of the legalides
of innovation and He economy shows He kind of social system in which
science is pursued. And He most challenging and pervasive scientific issues
of all, those of bioscience and the genetic process, are treated by one of the
primary explorers, James D. Watson. Thus, I have an exceptional and inviting
opportunity to report briefly on how He physical sciences (nowadays almost
qualifying as the "unnatural sciences") have developed as the intelligence
base, perhaps even the m~nd-set, for invention, discovery, and innovation
in world technology.
227
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228
WILLIAM 0. BAKER
CHRONOLOGY OF THE PHYSICAL SCIENCES
It is usually assumed that the development of the physical sciences comes
from atomic and molecular theory, postulated in Greek civilization and ex-
tending into the times of Dalton and other pioneers in Western Europe.
Concordantly, notions of waves and energy, of dynamics and mechanics,
arose from Newton, Helmholtz, and Maxwell, attended in all cases by the
indispensable Newtonian elements of calculus and other mathematics. These
matters all have moved aloe=, in the last several centuries and form the
conventional and highly productive basis for engineenn=, including modern
and sophisticated aerospace designs and vehicles.
But in this century particularly, new and compelling factors in the physical
sciences have arisen These are vastly more subtle than the reasonable and
even tactile phenomena of classical mechanics, fluid dynamics, and such
phenomenological descriptions of how matter behaves. They were foreshad-
owed by peculiarities of chemical reactions, whereby atomic and molecular
conversions were increasingly shown tO be the basis for one category of
transformation of matter.
The periodic table of the elements and its rationalization of compound
formation, electron exchange, the notion of ions in solution and of `'closed
shells" all raised compelling questions. They were also implied, but not
really foreshadowed, by the other domain, of thermodynamics, with Rum-
ford's demonstration of the interconversion of mechanical work and heat.
Especially central is the elegant elaboration of thermodynamics through the
Third Law of Nernst, and admirable connections of chemical equilibria and
free-energy-driven changes of state, analyzed by Gibbs and demonstrated
beautifully at various schools, such as at Berkeley by Gilbert N. Lewis.
What was being foreshadowed, of course, was quantum theory, quantum
mechanics, and quantum statistics. Einstein's photoequivalents, Sommer-
feld's operators, Heisenbera's uncertainty principle, and Bohr's structure of
the atom launched the heroic era of the fine structure of matter. This was
not much later than the time that J. J. Thomson, Rutherford, Roentgen,
Moseley and the others laid out what was in the nucleus. The electron was
the common interconnection (Figure 11. But it is important to remember that
these masterworks of physical and chemical meaning, came along in pieces,
not in unified understandings. Thus, although Rutherford and his school
notably extended ideas of the nucleus and electron, when Einstein had thought
of relativity and the interconversion of mass and energy (E = mc2), Ruth-
erford was dubious. He is quoted as saying, to economist and humorist Stephen
Leacock, "Oh, that stuff. We never bother with that in our work. '' !
Hahn and Strassmann then revealed what other particles could come out
of the nucleus in fission, and others showed what could be converted in
fusion, bringing us to a world where "unnatural science,'' and "unnatural
technology" combine, even to threaten nature on the planet.
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TTIE PHYSICAL SCIENCES AS THE BASIS FOR MODERN TECHNOLOGY
ELECTRON
CHARGE
in, MASS
MAGNETIC MOMENT
229
FIGURE 1 The electron (represented in this figure by its principal parameters) was
recognized as the basic scientific unit for electrical engineering,.
I have moved over this chronology of the physical sciences in order to
account for what is presented in the remainder of this chapter. I submit that
the physical sciences have moved since midcentury beyond their central
position in intellectual understanding of the nature of the universe through
physics and chemistry to a place where they will increasingly stimulate—
not just originate but stimulate large new frontiers of technology and en-
gineering. This relatively recent situation is already having back-reactions
of the kind identified by Harvey Brooks. But the complexity of such relations
and the implications for research, education, and the acquisition of under-
standing for its own sake are yet barely grasped.
Let me speculate briefly on how this phase of He physical sciences emerged.
It is said that the earlier preoccupation with individual atoms and molecules
detached the fundamentals of the then new physics and chemistry from
technical applications. The reason was that applications of new knowledge
in technology and engineering, almost always involved massive assemblies
of these new entities recognized as atoms and molecules. Even in the ;,as
phase, which was a less common condition, but always in liquids and solids,
there were numerous and complicated collisions and other interactions that
were thought to obscure, perhaps hopelessly, the great appeal of being able
to deal with individual particle behavior, or at least things beyond three-
body interactions.
The =,reat virtue (and indeed charm) of our century, especially of our last
half century, has been the casting off of those shackles of thought. More
importantly, it has been the inspired realization that the science of masses
of matter, namely the therrnodynam~cs noted earlier, and the mechanics of
individual molecules, atoms, ions, and particles could be wonderfully and
elegantly merged. Thus, the quantum mechanics noted as the portal to the
revolution, with its superb principle HE = Ed, is joined with the Second
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Representative terms from entire chapter:
physical science
230
WIGWAM 0. BAKER
Law of Thennodynamics AF = AlI - TAS in concepts and quantitative
formulations of matter and energy, of physics and chemistry. Hence, in
marvelous ways our descnpt~on of nature, while incomplete, is now inclusive
enough that we are seeing results as technology generated from the under-
s~dina of how matter could be adapted to economic and social needs.
One other element ought to be emphasized. It is Be work of the Braggs,
following RoentgeIl's discovery of X rays. They found ways to lay out Be
geometry, or the actual positions, of atoms and molecules In masses, by
wave diffraction of X rays. This was reinforced and generalized by Davisson
and Germer's discovery in Bell Laboratones of the dualism of waves and
electrons and their demonstration of electron diffraction from the interaction
of solid surfaces, as well as gases, with electron beams. Important industrial
differences between two classes of nylons (a polymer discovered by Carothers
at Du Pont) are revealed by X-ray diffraction showing how the molecules
associate (Figure 2)
SCHEMATIC Of SOLID
STRUCTURE OF ~LYA~ 1~
C~AtNS hlADE FROM O=-
NUMBERED ~)-AMINO ACIDS
OR EVEN NUMBERED
Dl(AMl~JES AND ACIDS)
~0=!
SC hiE - AT IC Of SOLID
STRUCTURE OF POLYAbtlDE
CHAINS MADE FROM EVEN-
NU~BERED CL-AMINO ACIDS
OR ODD NUMBERED
DI(AMINES AND ACIDS)
...o=< ~-~'0=<
TO-DO-: ~N-~-
'N-1~ 0- > <
- ''O=
THE PHYSICAL SCIENCES AS THE BASIS FOR MODERN TECHNOLOGY
231
APPLIED SCONCE SUPPORT FOR INNOVATION AND TECHNOLOGY
So now science is prepared to reinforce technology and engineering on
the basis of the fundamental units of nature, of particles and energy. And
new things are suggested and become technically attractive because of their
scientific reality and qualities. This can be illustrated by a few case studies
which in fact relate to major innovations and economic forces of these times
and the years ahead.
Crystals and Glasses
The first case study is about the solid state and the role of crystals and
glasses in modern manufacture and in high-performance systems, such as
aerospace, electronics, computers, information handling, and communica-
tions.
We see that the scientific concepts described are now permitting statistical
descriptions of real crystals. These crystals are regular arrangements of atomic
units (ions, molecules) in cells. They aggregate in various geometrical forms,
often randomly (Figure 31. But there are also vacancies or other imperfections
inside the cells as well (Figure 41. We now find that the strength of matter,
especially of metals and alloys, is often determined by the quantity and
mobility of these dislocations. Science is showing how they can be pinned
down, to inhibit the collapse of bridges and supertankers, for example
Computer models of how crystals are formed have been created by Jackson
and his contemporaries. The computer models illustrate how modern science
is guiding technical improvements in the solidification of matter where
hordes of atoms, not just two or three, are interacting (Figure 51. Yet the
composition of the crystals may be pure within parts per billion or better,
thanks to We zone refining discovered by W. G. Pfann as a foundation piece
for semiconductor electronics and, ~us, the modem electronics industries.
The scientific knowledge of what must and can be done in terms of Be
perfection and purity of these systems has supported technical advance, so
Hat electrical conductivity ranging over more than 10 orders of magnitude
can be carefully regulated. Further, these solids, as glasses, are forming a
new foundation for photonics, again with the requirements of purifier from
light-absorbing and light-scattering elements of parts per billion (Figure 6).
With silica glasses, the light transmission is as much improved in the last
decade as it was in 3 ,000 years of earlier history of making glasses transparent
(Figure 71. The latest figures on light beam losses of intensity—less than
0.16 decibel (dB) per kilometer of pathway in the glass—mean a "liquid"
so clear that to lose as much light as through an ordinary high-quality win-
dowpane would require that He new glass have a Pam a mile or so Hick!
As might be expected, some of this glass is very strong, with filaments
232
WI! ~ lAM 0. BAKER
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POLYCRYSTAL
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TEXTIJREB
FIGURE 3 The orderly structure of solids creates c~ystallites. which in turn may them-
selves be arranged in various orientations that govern useful properties of the solids.
FIGUF{E 4 C~rstallites forming from regular packing of atoms, ions, or molecules are
usually not quite perfect. Some missing units or vacancies occur, as shown in the schematic
building up of a solid from identical (model) cubes.
THE PHYSICAL SCIENCES AS THE BASIS FOR MODERN TECHNOLOGY 233
C_.
FIGURE 5 Real crystals form by a series of cumulative atom placements. apparently
aided by nuclei, or centers, such as in this computer-~enerated model conceived by
Jackson. Oilman. and their co-workers.
MAXIMUM TO LERAB LE CONCENTRATIONS
FOR VARIOUS IMPURITY IONS
Element
Iron
Co pper
Chromium
Cobalt
IV anganese
Nickel
\/anadium
Concentration,
parts per billion
20
50
20
2
100
20
100
Concentration calculated from published values. Only
one element is assumed to be present and In its worst
valence state. Maximum tolerable loss is assumed to be
20 dB/km.
FIGURE 6 Technical properties of engineering materials are often influenced by ex-
ceedingly small quantities of impurities, through composition, packing, and forces in the
solid state. Thus, the clarity of supertransparent light-guide glass is determined by the
indicated (tiny) tolerable portions of common metallic elements.
234
WILLIAM o. BAKER
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FIGURE 7 Illustration of the application of modern scientific pnoc~ples to Me punfication
of glass, showing improvement in clarity (reduction in losses). In the past decade photon
transmission has been increased almost as much again as the increase achieved through
empirical improvements of the preceding 3,000 years.
breaking only rawer uniformly in stresses of 800,000 to 1 million pounds
per square inch, or much closer to the theoretical strength of SiO2 than was
ever imagined to be possible.
Phase Rule Applications
Another fascinating example of how the bulk science of thermodynamics
and the fine structural concepts of crystal structure and atomic interaction
have combined is found in the modern applications of Me phase rule, enun-
ciated by Gibbs. Namely, Plewes Figure 8) and his contemporaries have
applied the complex distribution of phases in metal alloys, called spinodal
THE PHYSICAL SCIENCES AS THE BASIS FOR MODERN TECHNOLOGY
235
Decomposition (illustrated by classic gold-platinum liquid-solid curves; (see
Figure 9), so precisely for Cu-Ni-Sn systems that defects and dislocations
caused by the imperfect nature of crystals have been controlled in bronzes
to give 300 percent of more improvement in yield strength (Figures 9 and
10) This has been applied dramatically to bronze springs and relays (Figure 11)
and to a host of control systems for machines. But it represents, also, a
historic reminder of what the physical sciences lead to. Recall that the destiny
of kingdoms, of empires, and indeed of civilization was determined in the
Bronze Age by the strength, the hardness, of the weaponry, shields, and
spears made of bronze. Certainly much human ingenuity was devoted to the
improvement of such metals, yet In the 1970s, the latter part of the twentieth
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FIGURE 8 Plewes measuring new mechanics of special spinodal bronzes.
236
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FIGURE 9 Phase dials showing the fund~en~1 thermodynamic variations with
temperature in the composition of varying amounts of gold in platinum, from which it
is possible to select certain processing conditions yielding combinations of crystals of
optimal physical properties in the alloy
THE PHYSICAL SCIENCES AS THE BASIS FOR MODEM TECHNOLOGY
237
TYPICAL
MATERIAL YIELD STRENGTH
(1 03pSi)
ENHANCED
YIELD STRENGTH
(103psi)
Cu-5Sn (PtlOSPttOR BRONZE) 70 110 TEXTURED
Cu-12Ni 28Zn (NICKEL SILVER) 65 125 "
Cu-9Nt2Sn (.IIOD. CUPRONICKEL) 45 105 "
C~1.7Be (CI~PER BERYLLIUM) 145 170 "
Cu-9tl-6Sn (.IOD. WPRO~CKEL) 50 150 SPINODAL
FIGURE 10 Examples of structure enhancement compared to conventional yield strengths
of classic bronzes and other copper alloys. Note the twofold improvement of nickel-silver
alloy resulting from orientation of crystallites, and the threefold improvement of cupro-
nickel by spinodal control in the processed solid.
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FIGURE 1 1 Application of scientifically processed alloys in the manufacture of essential
commercial control equipment.
244
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FIGURE 20 Typical example of behavior of an unstabilized hydrocarbon exposed to air,
showing gradual early reaction followed by rapid oxidation.
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FIGURE 21 Example of important commercial stabilization of plastic against air oxi-
dation, as a function of weight percent of carbon added.
Surface Technology
Beyond Be pervasive domains of bulk matter and of media for light guides,
cables, and the like lie many other examples of how extensive innovations
and engineering are emerging increasingly from applied science. The wide
realm of surface technology is a compelling example.
THE PHYSICAL SCIENCES AS THE BASIS FOR MODERN TECHNOLOGY
245
Take first the films on which much of modern society depends, for instance,
paper. The control and fabncat~on of paper depend heavily on gauges and
machine responses generated by radioactive isotopes. Indeed, the modern
chronicle of surfaces and films, which define so much of our economy and
the substance of the information age, now illustrates a fine coalition of
atomistic science. In this, quantum mechanical knowledge of particles, fields,
charges, and bulk matter behavior developed from work in modern solid-
state theory and experiment, reveals the detailed configuration at surfaces.
For instance, semiconductors, transistors, and other junction devices are
activated electronically by certain additional atoms, called donors or accep-
tors, which shift the charge populations and field conditions in germanium,
silicon, indium phosphide, and so on. These effects are themselves deriva-
tives of the classically recognized electron-holding or electronegativity effects
in the elements. For decades, such behavior in ions and homopolar systems,
metals, and insulators has been a major topic in physics and chemistry.
Classes of matter can be categorized as to electrical conductivity by these
electronegativity effects (Figure 221.
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aTe
M-M' (METAL-METAL1 -
ELECTRONEGATIVITY DIRE
FIGURE 22 Diagram of electrical conducting properties of diverse classes of materials,
as determined by the electronegativity differences in their atoms, showing intimate con-
nection of atomic structure with technical electromagnetic behavior.
246
WI] ~ l~ 0. BAKER
Inventions for getting these atoms (e.g., arsenic, phosphorus, and others)
into the junction devices by diffusion and other clever methods dominated
the early periods of integrated circuitry (Frosch and Denck). However, ad-
ditional ways have especially been applied to Win films and surfaces. One
of the.best has been to accelerate ions, as Cockcroft and Walton have done
in the fundamental study of nuclei and of elementary particles. These ions
can then be implanted into the surfaces of the semiconductors and produce,
at appropriate depths and concentrations, the desired electronic responses.
The whole system of ion implantation is also interesting, for its potential
for improving wear on the surface of bearings, for generating new catalysts,
and especially for inhibiting corrosion. Every phase of its application in
technology, however, is based on the experiences of the original scientists
interested in colliding particles and elementary interactions.
A particularly fascinating modern instance of the continuing, versatility of
this science is how beams of ions can be directed down certain channels or
pathways in crystals or films to produce not only importantly modified struc-
tures, but also information from scattering and interactions about the nature
of their host solid (Figure 231.
Electron beams are among the simplest but most highly useful embodi-
ments of these particles. Here, in the work of J. West and collaborators, the
old technology of makin, electrets has been recast (by charging surfaces of
insulators). Now, all advanced telephones depend for their voice transducers
not on the century-old (and invaluable) performance of carbon microphones,
but on charged films of special polymers like polytetrafluroethylene. These
have been treated so that when bombarded with an electron beam (Figure 24)
the electrons are trapped quite permanently. The result compares with what
we have learned about the trapping of charges in silicon and germanium.
This realm of organic-polymer capture of electrons produces the most ef-
fective voice transducers so far achieved, and it is opening much more widely
the fields of teleconferencing and other special microphonic uses. It is also
suggesting new realms of scientific research related to energy processes in
living tissue, such as ion transport across membranes.
Particle bombardment can, of course, be extended—in the sense noted
earlier about the dualism of waves and particles (Bohr's complementarily
principle) to beams of photons, which are still smaller particles than elec-
~ons. In this case laser-pulsed beams on the surfaces of crystals produce
valuable and increasingly used effects A burst of photons lasting a hundred-
millionth of a second from a laser of 532-nanometer wavelength causes
heating at a depth of a micrometer in a silicon surface. This heating, is
immediately quenched, at about a billion degrees Kelvin per second transient,
by the solid below the surface. Vanous important metastable conditions can
thus be obtained, as the current work of W. Brown and his associates dem-
THE PHYSICAL SCIENCES AS THE BASIS FOR MODE~ TECHNOLOGY
-- ~
CHANNELING
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200 °~00 600 800
ANNEALIN(; TE~PERAT\IRE (°C1
FIGURE 23 Examples of distribution of ions implanted by nuclear accelerators into single
c~ystals of silicon, as determined by the directions in the crystal and subsequent heating
to redistribute the acceptor (boron) or donor (phosphoms) units.
248
WIGWAM 0. BAKER
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FIGURE 24 Schematic of implantation of electrons in polymer films to form long-lived
elec~ets, which then can act as efficient microphones and other electromechanical ~ans-
ducers.
onstrates, aloe, with that of others working in this field. Indeed, this process
can be regulated so that the entire heating effect is due to electron-photon
collisions, rather than a conventional phonon excitation by movement of the
bulk atoms in the solid.
Nuclear Science and Radioisotopes
Recall, also, the already vast and growing role of the science of chart,ed
particles in the characterization of matter and its reactions, far beyond the
surface and film phenomena. Namely, the group of more than 1,600 new
isotopes created by nuclear reactions (particularly of neutrons), along with
300 naturally occulting stable isotopes, form Me corpus of technology for
Facing chemical reactions. These methods are especially dominant in research
on organic and living matter. Analysis using, these schemes commonly in-
volves radioactive counting instruments and mass spectroscopy, in which the
isotopic atom becomes a charged particle. Likewise, in reference to We use
of unstable nuclei with their useful radiation output, the synthetic technetium-
99 derived from neuron bombardment of molybdenum is the most widely
THE PHYSICS SCIENCES AS THE BASIS FOR MODEM TECHNOLOGY 249
used Isotope in nuclear medicine nowadays. However, these cases are but
symbolic of the immense scope of elementary- and radioactive-particle sci-
ence in support of a multitude of industrial, governmental, and social initia-
tives.
I-his delicacy of identifying atomically the behavior of virtually all tech-
nical and en;,ineenng systems has, of course, brought along many more
conventional analytic and control schemes, themselves derived earlier from
the principles of physics and chemistry. Optical spectroscopy is a distin-
guished example; now with Rarnan surface-enhanced spectra, the ordinary
gas-phase sensitivity may be increased about a million times, to the detection
of 109 molecules or less. Moreover, using laser activation, studies at Oak
Ridge National Laboratory have observed single atoms of cesium in a cloud
of 10~9 other atoms. Similarly, David Joy's Nonimpact spectroscopy can
determine light elements quantitatively in a sample whose total mass may
be only 10- ~8 a millionth of a millionth of a millionth of a gram. Opt~cal-
emission spectroscopy can respond to as few as a million molecules per cubic
centimeter, and fluorescence following laser exposure to liquid jets from
high-pressure liquid chromatography has permitted the detection of a billion
or less aflatoxin molecules per cubic centimeter.
SCIENCE SUPPORTING MEASUREMENT AND SYSTEMS
Physical science thus has not only provided a conceptual and intellectual
base for modern technology, but repeatedly has injected quantification. In
this way the entire character of technical engineering and economic operation
has been enhanced beyond the empincal, often purely descriptive, stages on
which manufacture and mining depended for a thousand years.
In some fields of the highest innovation and sophisticated technology, we
are now seeing the elegant principles of twentieth-century physical science,
along with the experiments and techniques achieved, being combined into
operational systems for dramatic advances in economic and social functions.
These are seen especially in Me new arenas of communications and com-
puters; of inflation handling; of sensing, command, and control; of in-
dustnal automation and national security; and indeed (in the wide range of
electonics, photonics, and circuitry) in the new systems of personal action,
education, and entertainment. These resources universally involve semicon-
ductor junction devices, which, in turn, have to be assembled with metallic
conductors and strong organic or inorganic insulators and with various heat
and mechanical qualities. In this systems realm, atoms, molecules, charges,
and waves must be made to perform with great precision. This need is being,
met by synthesizing, preferably in Din film- and surface-controlled forms,
new states of matter (Figure 251. This has been done especially by R. Dingle,
A. C. Gossard, and W. Wiegmann, based on the liquid-phase epitaxy work
250
WIl4AM 0. BAKER
of M. Panish, the film studies of J. M. Poate, members of AT&T Bell
Laboratories, and now the contributions of a variety of workers in other
laboratories around the world.
These schemes of generating beams of atoms or molecules that then form
condensed matter of predetermined, and often unprecedented, properties si=,-
nify a heroic combination of physics and chemistry, of Gibbs's phase prin-
ciples and Heisenberg, Sommerfeld, and Einstein's quantum mechanics, of
the Braggs' and Davisson's structural diffraction waves in crystals, of He
Bardeen-Brattain-Shockley discovery of the transistor effect, and, win the
solid-state injection laser embodying Schalow and Towne's revelation of new
forms of light itself, the laser
In examining a little further this making in the laboratory, and now in He
factory, of unique and productive forms of matter, it should be emphasized
that this is only the beginning. For in the times ahead, the exposed surfaces
of the manufactures of most industries may involve these same synthetic
processes. It is already fair to say, however, that the digital systems (com-
puters, communications, and controls) on which modern industry and gov-
ernment increasingly depend will shortly be using these schemes throughout.
Thus, since as noted, this technology does involve nearly every aspect of
He wide reaches of physical science gained during this century, we have a
powerful answer to questions of the practical values of research. When the
press and politicians question its relevance or economic return, it can be
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FIGURE 25 Arrangement of molecular beam and atomic beam generators for gallium
and arsenic to create new semiconductor films of unique quality for digital circuitry, such
as in high-performance computers.
THE PHYSICAL SCIENCES AS THE BASIS FOR MODEM TECHNOLOGY
HIGH blOBILIlY MODULATION-DOPED SEMICONDUCTORS
251
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FIGURE 26 Electron micrograph showing the molecularly layered structures deposited
by the molecular beam and yielding charge mob~liiies and other technological advantages
previously unknown.
stated Mat there is simply no evidence Mat this synthesis of new states of
matter by molecular-beam deposition and epitaxy could have happened em-
pirically and without Me vast scientific base summarized here.
Indeed, the behavior of the domains produced, for instance, win gallium
arsenide and alternating additions of aluminum gallium arsenide in Me pres-
ence of a silicon substrate, exhibits charge mobilities never before achieved
(Figure 261. The resulting transistors are already He essence of supercom-
puters and superspeed circuitry. However, the ~eoreuca1 significance of
these new structures is also profound. For instance, it happens Hat quantum
mechanics is generally taught, and was early conceived, in terms of the
quantized behavior of a particle in a box. The Hamiltonian operator dominant
in Schrodinger's equation is illustrated as describing the behavior of such a
model. The charges in He layered structures produced by molecular-beam
epitaxy (Figure 26) are the best, and in some ways He only, case in which
an experimental quantum particle in a box has been achieved. Thus, we are
seeing In this, as in so many other cases of the development of solid-state
science, and now in photonics, the interaction of technology in stimulating
further scienuf~c insight.
Remarkable scientific combinations win technological outputs are also
proceeding rapidly in the molecular-beam epitaxy processes themselves
(Figure 271. For instance, M. Panish, referred to above with regard to his
earlier work in liquid-phase epitaxy, has now introduced gas-phase sources
252
WIt r l~ O. BAKER
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FIGURE 27 Example of the precise and sophisticated high-vacuum apparatus developed
by Hags~om to control and analyze molecular beam epitaxy and the synthesis of new
thin crystal forms of matter.
Of elements to form the beams. This replaces having to depend on sometimes
poorly defined solid reservoirs for atom and molecule emission. This flex-
ibility has moved forward with W. Tsang into ''chemical-beam epitaxy,"
in which all of the component elements come in gas form, such as metallo-
organic compounds of gallium and indium. This exceedingly attractive sys-
tem, which seems certain to have a strong impact on heterogeneous-catalysis
creation in the chemical industry, on surface stabilization, and in various
other applications mentioned, is termed MOCVD metallo-organic chemical
vapor deposition. It is being controlled by highly sophisticated flow tech-
niques regulated by microprocessors and yielding kinetics of particle synthesis
in the high vacuum, which are themselves of deep interest to the chemical
and materials industries.
It should be emphasized again at this point that the universe of innovation
supported by atomic and molecular surface and film synthesis is a striking
derivative of the long-tenn studies of high vacuum and surface purification,
epitomized by the research of Homer Hagstrom. On the one hand, recall that
energy states and surface physics were essential in the discovery of the
transistor; they were, in fact, the crucial features in Bardeen's pioneering
theory. Beyond that, however, the superb experimental extensions of surface
physics by Ha:,strom and his associates are dependent on the achievement
THE PHYSICS SCIENCES AS THE BASIS FOR MODERN TECHNOLOGY 253
of unprecedented cleanliness and surface characterization involving, among
other things, consistent and controllable vacuua of 10- ~: torr or better. This
is an emptiness beyond that of outer space, and yet it has become a factory-
controlled process (Figure 271. The intense importance and decisive role of
these researchers in the electronic-photonic-matenals regime is well sym-
bolized by the diagram of Hagstrom's latest research apparatus (Figure 28),
which includes working units of ultraviolet, photoemission, energy-loss, and
Auger-electron spectroscopies. These are all notable examples of modern
quantum physics, including electron-diffraction and ion-neutralization spec-
troscopy, which have had their own historic roles in the physical sciences
of the twentieth century.
In this context it is also appropriate to denote the rapidly moving frontier
use of this science and technology in electronic and photonic systems in-
novation. Thus, the selectively built heterostructure transistor obtained from
molecular-beam epitaxy, including a multilayered sandwich of ultrapure gal-
lium arsenide with aluminum gallium arsenide layers that are heavily doped,
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254
wI] r BAD 0. BAKER
has been shown by J. DiLorenzo to provide a new rin:,-oscillator circuit. It
is effectively operating as a switch at 90 billion operations per second, far
beyond anything ever before reached in integrated circuitry. Over embod-
iments provide such records as frequency dividers working at 10 gigacycles,
at low temperatures.
The work of R. Dangle, [I. Stunner, and A. Gossard has indeed already
shown the doubling of electron mobility in the gallium arsenide-alum~nunn
gallium arsenide case referred to earlier. Electron monon is 20 tunes as fast at
low temperatures. This will undoubtedly be developed into important structures
for photonics, eventually including integrated optoelectronic circuits. In this
regard ge:Tnanium, silicon, and Weir combinations, which yield stained su-
perlat~ces, have already been achieved by John Dean of Bell Laboratones.
Also, Julia Phillips has grown calcium fluoride on silicon, so Mat staking new
insulator-semiconductor systems are in progress. Likewise, these advanced em
itaxial techniques are being used in Be production of new magnetic rare eats
systems and in superconductors. Accordingly, our expectations of extensive
innovation from this new basic science are appropnate.
Finally, it is appropriate to accent In every connection that physical science,
to which I attribute so much of the base for the technology and economy of
this age, is, in turn, heavily dependent on mathematics and the conceptions
of logic and encoding that are Be base for computers, analysis, and Be
treatment of atomic and molecular events. Newton and Maxwell were referred
to at the beginning of this chapter; we should also remember the host of
mathematicians who mastered statistical mechanics, group theory, symbolic
logic, and an array of other elegant representations of Be mind. While our
progress in physical science is an adornment of civilization, its modern
excellence and extent derive especially from bow the content and Be modes
of Bought Mat mathematics has engendered. Overall, it is gratifying that the
science of Aristotle and Plato, of Newton and Einstein, is now so well joined
win He technology of humankind, which I have described elsewhere* as
"~e ways of making Dings and doing things."
*[Random House Encyclopedia (New York: Random House, 1977), p. 1578.
