Robert Sproull, the director of AREA (Advanced Research Projects Agency) in the Pentagon, recorded that Pennsylvania State University and Carnegie Institute of Technology first made proposals in 1957 for “interdisciplinary block funding” in what would essentially become “materials” research. But it was the industrial push (by W.O. Baker of AT&T Bell Laboratories and C.G. Suits of General Electric) that helped ARPA start the funding of 12 interdisciplinary materials research laboratories (IDMRLs) between 1960 and 1963. Pennsylvania State University was added in 1963 as a special modest grant limited to materials preparation (synthesis and processing). NASA and the Atomic Energy Commission added six more within two years. The first interdisciplinary degree program in “materials” (then called solid-state technology), administered directly by a graduate school committee drawn from 10 departments, was started under my chairmanship, at Penn State in 1959-60. Probably the first departmental degree program in which a metallurgy department expanded its scope (and changed its name) to include other materials was started at nearly the same time at North western University by Prof. M.E. Fine. It is noteworthy that at least in these two cases the intellectual and curricular argument for integration of degree work preceded the research grants and organization. These two separate patterns have both now permeated the entire national system, and we should clearly distinguish between them. By 1969 the first national colloquy on materials, held at Penn State and published under the title Materials Science and Engineering in the U.S., took an evaluative look at materials education.

The fabrication of a state-of-the-art silicon chip consists of a carefully composed sequence of “steps.” The length, complexity, and place of each step within this process is analogous to that of a musical phrase within a long sonata. Just as a sonata consists of a series of recurring but evolving themes, a “process” utilizes a number of basic techniques that recur in a variety of contexts. A typical modern process consists of about 350 “steps.” Roughly a fifth of them belong to the class of ionassisted processing. These range from a variety of ion implantation modules, through sputter deposition and reactive ion etching of thin films, to photoresist etching and ashing. Ion-assisted processing thus has a role of major technological importance. With the range of new processes currently under active research, this trend seems likely to continue.

The technological applications of ionassisted processing rest on the basic concepts developed in research over the past 30 years. This special issue of the MRS Bulletin reviews the fundamental concepts that underpin this processing today, and highlights areas of current research which may have future technological potential. The emphasis is placed heavily on silicon, both for illustrative purposes, and because Si processing is the major customer for ion-assisted technology. The articles pinpoint areas where materials research can play a critical role in establishing the fundamental understanding needed for a realistic assessment of technological potential.

The behavior of successful manufacturing companies has changed in response to the accelerating pace of technological development in recent years. Manufacturing firms are under greater pressure than ever to bring new products and processes to market rapidly, with lower costs and higher quality than achieved in the past. In addition, the establishment of a global economy no longer dominated solely by the United States has required firms to expand their outlooks and horizons. Successful firms must take a multinational view, understanding and serving local customer needs while maintaining the efficiency of a global enterprise. This requires greater flexibility in manufacturing and distributing new products.

As the business environment for materials manufacturing changes, so too does our measure of materials performance. Traditionally, materials scientists and engineers have emphasized processing, structure and properties, and the way they come together to produce performance of a product in a given application. However, as shown by Figure 1, there are several additional dimensions to performance. In particular, successful commercial performance depends not only on the physical properties of the material but also on our ability to shape it into a useful object in an economical and timely manner. Without shape, the product cannot serve its intended function, and without economical production, the product's usefulness is limited to fewer, higher value applications. Achieving more rapid and more consistent commercial success from advanced materials requires emphasizing not only the process by which the material is made but the process by which the material achieves its geometry and function, while at the same time maintaining the ability to bring these materials to market rapidly at an economical price. Indeed, the cost delay in commercializing a new material can be the key to success or failure.

The high-transition-temperature superconductors (HTS) present a number of challenging materials science problems whose solutions must precede their use in applications. This article offers a view on our collective progress toward resolution of one central HTS issue, the “weak-link” character of high-angle grain boundaries.

Why Are HTS Grain Boundaries of Such Interest?

The properties of high-angle grain boundaries control the macroscopic electromagnetic character of all superconducting copper oxides that are produced in polycrystalline form. In particular, grain boundaries limit the transport critical current density (Jct) and determine its dependence on applied magnetic field (H) and temperature (T). Jct is the maximum macroscopic current density that the superconductor can support in the nondissipative state. H and T are the two most important environmental variables for applications of superconductivity. Thus, the Jct(H, T) characteristic largely dictates the types of applications for which a superconducting material can be used successfully.

High-angle grain boundaries are the immediate obstacle to further development of materials for applications that require large Jct values in high magnetic fields. The problem arises because most high-angle grain boundaries act like Josephson-coupled weak links. The characteristic properties of such junctions are a reduced zero-field Jct value and, more importantly, a strongly magnetic-field-dependent Jct that can decrease by more than an order of magnitude in even weak fields of a few millitesla (Fig. 1). Such Jct(H) characteristics are clearly a very serious problem for high-field magnet applications such as motors, generators, energy storage systems, and MRI machines.

Art has as many meanings as contexts in which it operates. It can mean surface decoration or the integral sum of parts and whole which a historian analyzes as structure using visual, musical, theatrical or other criteria. Art serves as decoration, but also serves to signal or sign a particular meaning. Art often confers an elite social status on its patrons or provides goods which support the power and prestige of a special group or person. Art is also used to describe the experience of viewers, usually as “aesthetic experience”; for instance, we experience art as beauty, as a shared emotional experience or empathetic understanding, or as interactive play or a process of performance by which we investigate or relate ideas, occurrences, or objects and give them meaning.

Technology, in contrast, is usually defined as “praxis” and involves doing things, as a craft practice involving materials selection and refinement, followed by making those materials into useful things, artifacts, or objects which serve useful functions for individuals, a social group, class, or culture. The products of technology can be useful as tools that enable a task to be accomplished, or as products which satisfy subsistence needs, or devices, or even practical ideas. When put to use, they enable travel, communication, transportation of goods, or control of energy. But technology has another meaning which is often thought to be less useful, namely technical marvels—things which amaze or surprise us. Some examples are the mechanical automatons of the 17th and 18th centuries, the latest computer game, a special way of hearing or seeing, or even the gas and light spewing magic machines described as being used in Greek temples to get peoples' attention. Another example is the technology described by the 11th century monk Theophilus, used to equip a church, from bells and censors, to glass windows and painted walls. In these examples, doing technology or learning to use technological marvels is a way of almost magically extending our own power and understanding beyond ourselves.

The October issue of the MRS Bulletin focused on two areas of research in biomolecular materials; biomineralization and protein fibers. In addition, the development of a new carbohydrate-based material with a variety of novel properties was discussed.

In this issue, we turn to two other types of materials based on biological systems: (1) polymers and other materials produced through enzyme-catalyzed biosynthetic reactions and (2) protein and lipid complexes based on biological membrane structures. In each case, as in the October issue, a discussion of how Nature produces and uses these materials is followed by reports describing manipulations of these systems to enhance their properties for nonbiological applications.

In the October issue, Kaplan and Cappello discussed in detail the synthesis of proteins. They described how living organisms expend a very large fraction of their energy producing these polymers to grow and repair damage to their bodies. (The other major fraction of their energy is dedicated to maintenance of brain function). Synthesis of carbohydrates, lipids, and other materials, however, is achieved through a somewhat more complex process. The organism outlines a pathway that consists of a sequence of reactions; each reaction converts a substrate-the product of the preceding reaction-to a product which is the substrate for the next reaction. The net result of the action of the pathway is the conversion of a nutrient to a useful material, often of far different chemical structure.

One of the simplest ways to measure the mechanical properties of a thin film is to deform it on a very small scale. Because indentation testing with a sharp indenter is one convenient means to accomplish this, nanoindentation, or indentation testing at the nanometer scale, has become one of the most widely used techniques for measuring the mechanical properties of thin films. Other reasons for the popularity of nanoindentation stem from the ease with which a wide variety of mechanical properties can be measured without removing the film from its substrate and the ability to probe a surface at numerous points and spatially map its mechanical properties. The utility of the mapping capability is illustrated in Figure 1, which shows several small indentations made at selected points in a microelectronic device. The hardness and modulus of the device were determined at each point. In addition to microelectronics, nanoindentation has also proved useful in the study of optical coatings, hard coatings, and materials with surfaces modified by ion implantation and laser treatment.

Following D. Allan Bromley's plenary lecture at the 1991 MRS Fall Meeting, the MRS Bulletin conducted a telephone interview with him on December 27. The following is an edited version of that interview. Bromley is Assistant to the President for Science and Technology and also Director of the Office of Science and Technology Policy (OSTP). His plenary address is published in the Bulletin's Material Matters column this month.

Bulletin: You have obviously managed to sustain excellent relations with the administration while also being an effective spokesperson for science. During your term in office, both the FCCSET (Federal Coordinating Council for Science, Engineering, and Technology) and PCAST (President's Council of Advisers on Science and Technology) committees have been revitalized. Could you briefly describe the impact of their increased effectiveness?

Bromley: I think the best way to do that is to indicate what they're doing now. The FCCSET was established in 1976 at the same time that the OSTP was put in place through joint action of the administration and Congress. The charge to the Council was that of integrating and coordinating issues that transcend the boundaries of any single agency, so it focused on interdisciplinary and multi-agency programs. In the early days, however, it did not function as had been intended because the members were at too low a political level. Decisions reached in the Council could, later in the budget process, be disowned by more senior people in the agencies. Having recognized that problem and with strong support from President Bush, I was able to reconstitute the FCCSET so that its members now consist of secretaries or deputy secretaries from all the relevant agencies, as well as heads of independent agencies like EPA, NSF, and NASA.

An energetic ion undergoes two major mechanisms of energy loss: (1) screened Coulomb collisions with target atoms (nuclear stopping), and (2) interactions with bound or free electrons in the solid (electronic stopping). This article discusses how these two energy-loss processes—and related quantities such as the ion range, collision cascade behavior, sputtering, and spike effects—depend on the experimental parameters of beam energy, atomic number, and target density. We restrict ourselves to an individual incident ion and a time scale (~10−12 s) sufficient for the cascade to fully develop (Figure 1), but short enough for subsequent quenching or diffusion processes to be ignored. What happens at longer times and higher ion f luences, due to diffusion and cascade overlap phenomena, is treated in the article by Brown and Ourmazd in this issue of the MRS Bulletin.

Energy-Loss Concepts

Figure 2 summarizes the velocity (ε1/2) dependence of the two energy-loss processes, nuclear stopping (dε/dρ)n and electronic stopping (dε/dρ)e, in terms of the dimensionless Thomas-Fermi (TF) energy, ε, and length, ρ, units derived by Lindhard. The energy unit ε is defined as the ratio a/b where a is the TF screening length (typically, ~0.01 nm) and b is the distance of closest approach in an unscreened head on collision. The following simple relationship exists between TF and lab energies.

where M1, Z1, M2, and Z2 are the masses and atomic numbers of projectile and target atoms.

The idea of engineering the detailed microstructure of materials by controlling the chemical synthesis process at an atomic level is particularly interesting for high-temperature superconductors (HTS) and many other oxide compounds. The prospect of integrating such materials as superconductors, ferroelectrics, and compounds with interesting magnetic properties into samples with atomic precision and perfect heterojunctions would seem to open the door to many novel possibilities. These materials, while complex, fundamentally have planar crystalline structure, and thus allow for the possibility of molecular and even atomic layer engineering. The “zoology” of phases that has been discovered in the study of naturally occurring HTS compounds is by now quite complex and illustrates this theme. While CuO2 planes are universally important for superconductivity, there is much more flexibility and variety in the other kinds of layers that act to complete the crystal structure. Examples of such “other” layers include alkaline earth oxides like SrO and BaO, copper oxide “chain” layers and rock-salt-like (BiO)2 bilayers, to name a few important ones. Moreover, families of very similar polytype phases have also been identified, in which members of each family differ principally in the number of copper oxygen planes within each formula unit.

This great richness of structure sets a pattern that invites the imagination to devise new materials and heterostructures and has motivated the development of synthesis techniques that control growth at the level of the submolecular—atomic layers. For instance, with adequate control of the growth process, highly metastable phases, such as Bi2Sr2Ca7Cu8O20, can be synthesized and their properties measured.

In April 1991, President Bush unveiled “America 2000,” a national strategy for improving the overall performance of students in America's school system. He and the nation's governors developed the strategy as a result of the historical Charlottesville Summit, held in Virginia in 1989.

America 2000 focuses on six national education goals, three directly related to mathematics and science education. Goal 4, in particular, states that “by the year 2000, US. students will be first in the world in science and mathematics achievement.” By the Year 2000, the report of the Federal Coordinating Council for Science, Engineering, and Technology (FCCSET) Committee on Education and Human Resources (CEHR) details the federal government's strategic objectives for meeting this goal.

The primary objectives outlined in the report focus on (1) improving student performance, (2) providing a strong precollege work force, (3) ensuring an adequate pipeline for the science and engineering work force, including increased participation of underrepresented groups, and (4) improving public science literacy. I'll discuss later how a revolutionary materials science and technology curriculum developed by Pacific Northwest Laboratory (PNL) and Northwest teachers has proved to be a model for meeting these objectives.

The FCCSET/CEHR report identified precollege as the educational level receiving the highest priority. At this level, the strategy for achieving the objectives is structured around (1) improving teacher preparation and enhancement, (2) reforming curricula, (3) organizing systemic reform, and (4) providing student incentives and opportunities.

To avoid misinterpretation, the term “art-and-technology” should be hyphenated because we are looking at an integrated art form which developed, roughly, during the past 70 years (since Naum Gabo's virtual volume, Kinetic Construction, Berlin, 1920). Art-and-technology results from “incorporated” contributions of art, science, and technology or, better, from artists, scientists, and engineers (plus industry, business, government, etc.). Although art-and-technology has frequently been bad-mouthed or even pronouned “dead” by advocates and practitioners of pure art as well as science and technology, it is alive and well and enjoying more vitality, variety, and expansion than ever before. It is currently the only expanding field in the arts; it feeds vitally into technology and industry—most visibly in entertainment but it also provides stimulus beyond fun to areas of science and engineering where “art applications” have abounded since the advent of photography and its vast consequent uses in science.

We can claim an eloquent tradition for art-and-technology in ancient historic, cultural manifestations such as the Egyptian pyramids and their “environmental” scale or the Greek theater with its elaborate stage machines. We are aware of elements of that tradition when we observe contemporary art-and-technology such as sky and space art (Figures 1 and 2), computer-generated virtual reality, performance with medical inquiry and medical apparatus, and art concepts inspired by molecular biology (Figure 3). Emphasis of search—whether artistic/expressive, conceptual/philosophical, or inquisitive/scientific—depends on taste and motivation. However, Leonardo is an undisputed idol to both artists and scientists.

Poets and philosophers have, through the ages, viewed organisms as the embodiment of the mysterious “Vital Force,” a unique non-earthly element required for the functioning of life processes.

Biologists have seen, in living organisms, an adaptive, self-reproducing, evolving collection of molecules acting solely according to the laws of chemistry and physics.

Historians speak of the iron or bronze ages and, more recently of the plastics (polymers) and the silicon ages. Materials science departments speak of metals, alloys, ceramics, and perhaps polymers—but not of genes.

The “common man” has, it must be admitted, seen living organisms as a source of useful and important materials—wood for building; cotton, silk, and other fibers for textiles; horn, shell, and bone for tools and weapons; fats for lubricants; fur for clothing

But, in fact, few of us now think of materials when we think of living things. Neither do we think of DNA, protein, and carbohydrates when we think of materials.

No, biologists have not been blackballed by materials scientists, chemists, and physicists. Until recently, they neither understood the processes by which life produces its materials nor even conceived of manipulating those processes to tailor the properties of the materials to our needs. Only within the past few years has the “biological revolution” expanded our understanding of the molecular basis for biological phenomena and our ability to control them. It is only now, for the first time, that one can point to a legitimate field of science based on mimicking, adapting, and controlling biological systems with the goal of producing novel materials with important, unique, and useful properties.

The use of manmade materials progressed rather slowly until the science and technology of metals, refractories, and glass burst forth in the mid-1800s and continued its infancy through the first decades of the 20th century. In fact, much of the scientific wherewithal in industrial nations focused on the development of manmade materials from the standpoint of properties and fabrication processes. From the discipline of metal physics, which emerged in the 1930s, and from the scientific activities in ceramics, polymers, and electronic materials that blossomed in the 1940s and 1950s, a science and engineering base was established, enabling advanced materials and components to be fabricated, often for specific end-user applications. The molecular engineering of crystals, for example, has its roots in von Hippel's studies of dielectric materials at the Massachusetts Institute of Technology, which began in the 1930s. In this time frame, society, which had primarily used such materials as wood, gypsum, clay, copper, zinc, lead, and iron, turned to a broader set of materials to meet new uses. These new applications required an understanding not only of the composition of matter, but of novel and difficult processes as well. Research specialties broadened.

From the late 1950s to the present, the knowledge base for materials and components has exploded. In this period, the scientific and technological field of endeavor—materials science and engineering (MS&E) — evolved from a collection of discrete, disparate arts and crafts with varied amounts of science and practitioners who generally did not stray from their own specialties to a more diffuse field where researchers take a broader approach to materials research and practice.

Man has walked on the moon, sent probes to or near the surfaces of Mars and Venus, and dispatched vehicles to fly near comets, asteroids, and the outer planets and their moons. In contrast, a journey to the center of the Earth remains as unattainable and fictional as in Jules Verne's day. We know the interior of our planet from several types of evidence: direct sampling of rock brought to the surface by geologic process from depths no greater than 200 km, remote sensing especially by seismology (the study of natural or anthropogenic sound waves passing through the Earth), inferences from the chemistry of meteorites and from other geochemical arguments, and laboratory and computational simulations of the conditions at depth. The laboratory study of Earth materials at high temperatures and pressures is the subject of this review. In a sense, the basic question of deep earth geophysics is a peculiar sort of inverse problem in materials science; rather than determining the properties of a given material, one seeks to find materials, under constraints of natural elemental abundances, which have properties consistent with seismological and other geophysical observations.

What are the “hard facts” about planet Earth as a material system? Its radius and mass are well constrained, as are pressure and density as a function of depth (see Figure 1). Its vertical temperature distribution is less well known, but it is clear that the interior is hot, with temperatures in the mantle reaching perhaps 3000 K and in the core perhaps 6000–7000 K.

A wide variety of microorganisms accumulate an optically active polymer of D(−)-3-hydroxybutyric acid, P(3HB), as an intracellular storage material of carbon and energy. The P(3HB) was first isolated from Bacillus megaterium in 1925 by Lemoigne. Many prokaryotic organisms, such as bacteria and cyanobacteria, have been found to accumulate P(3HB) up to 80% of their cellular dry weight when growth is limited by the depletion of an essential nutrient such as nitrogen, oxygen, phosphorus, or magnesium. Recently, many bacteria have been found to accumulate copolymers of D(−)3-hydroxy-alkanoic acids with a chain length ranging from three to 14 carbon atoms. In addition, 4-hydroxybutyric acid was found as a constituent of bacterial polyhy-droxyalkanoates (PHA).

Bacterial PHA polymers have attracted much attention as environmentally degradable thermoplastics for a wide range of agricultural, marine, and medical applications. PHA is degraded in soil, sludge, or sea water. Some microorganisms such as bacteria and fungi secrete extracellular PHA depolymerases to degrade environmental PHA and utilize the decomposed compounds as nutrients. In this article, I report the metabolism, production, and properties of bacterial PHA.