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Nanoscale: Visualizing an Invisible World

Words by Kenneth S. Deffeyes
Illustrations by Stephen E. Deffeyes
Copyright Date: 2009
Published by: MIT Press
Pages: 144
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  • Book Info
    Book Description:

    The world is made up of structures too small to see with the naked eye, too small to see even with an electron microscope. Einstein established the reality of atoms and molecules in the early 1900s. How can we see a world measured in fractions of nanometers? (Most atoms are less than one nanometer, less than one-billionth of a meter, in diameter.) This beautiful and fascinating book gives us a tour of the invisible nanoscale world. It offers many vivid color illustrations of atomic structures, each accompanied by a short, engagingly written essay. The structures advance from the simple (air, ice) to the complex (supercapacitator, rare earth magnet). Each subject was chosen not in search of comprehensiveness but because it illustrates how atomic structure creates a property (such as hardness, color, or toxicity), or because it has a great story, or simply because it is beautiful. Thus we learn how diamonds ride volcanoes to the earth's surface (if they came up more slowly, they'd be graphite, as in pencils); what form of carbon is named after Buckminster Fuller; who won in the x-ray vs. mineralogy professor smackdown; how a fuel cell works; when we use spinodal decomposition in our daily lives (it involves hot water and a package of Jell-O), and much more. The amazing color illustrations by Stephen Deffeyes are based on data from x-ray diffraction (a method used in crystallography). They are not just pretty pictures but visualizations of scientific data derived directly from those data. Together with Kenneth Deffeyes's witty commentary, they offer a vivid demonstration of the diversity and beauty found at the nanometer scale.

    eISBN: 978-0-262-32252-2
    Subjects: Biological Sciences, General Science

Table of Contents

  1. Front Matter
    (pp. i-v)
  2. Table of Contents
    (pp. vi-vii)
  3. Introduction
    (pp. viii-ix)

    Before 1900, virtually all science concerned things that you could see. Telescopes and microscopes extended our vision, but before Einstein’s 1905 papers on fluid properties (including Brownian motion), belief in the existence of atoms and molecules was optional; if they did exist we knew only that they were too small to see with a visible-light microscope. Einstein established the size, and therefore the reality, of atoms and molecules (see p. 130).

    How can we “see” the atomic structure of our world? Most atoms are roughly 0.2 nanometers in diameter, where a nanometer is a billionth of a meter. Even a...

  4. 1 Air
    (pp. 1-1)

    Air is a mixture of several kinds of molecules. Nitrogen atoms, shown in blue, combine in pairs and form 77 percent of the air. Oxygen atoms, the red pairs, amount to 22 percent. Argon (violet), which does not form chemical bonds, is shown as single atoms that make up most of the remaining 1 percent. Carbon dioxide, despite its role in Earth’s climate, amounts to only 0.03 percent. Carbon dioxide is identifiable in the illustration as two oxygen atoms linked by a small black carbon atom.

    Although we all think of atmospheric oxygen as A Good Thing, there is an...

  5. 2 Ice and Water Vapor
    (pp. 3-5)

    The lower part of the illustration shows water molecules as they occur in water vapor (steam). Each oxygen (red) is accompanied by two hydrogens (white); with the two hydrogens separated by an angle of 105 degrees. The arrangement is irregular, both in the spacing between molecules and in their orientation.

    At the top is the structure of crystalline ice, as first determined in 1935 by Linus Pauling. Each oxygen has four nearest neighbors and the angle between nearest neighbors is 109.5 degrees. It takes only a minor distortion to fit the preferred 105 degrees in the isolated water molecule into...

  6. 3 Gold
    (pp. 7-7)

    Pure gold consists of gold atoms packed neatly together in a cubic array. The sticks between atoms show the connections between nearest neighbors. Pure gold is soft and easily melted. (Metallic bonding is discussed in the next section.) Also, because gold sometimes occurs as gold grains in river gravels, it can be mined with simple tools. As a result, we find beautiful gold jewelry thousands of years old. Gold was the first metallic resource to be mined and used.

    Gold has two major uses: as a material and as a form of money. Because it does not corrode, gold is...

  7. 4 Chemical Bonds
    (pp. 9-9)

    Linus Pauling’s 1954 Nobel Prize was for explaining “the nature of the chemical bond.” He showed that there were several, quite different, kinds of chemical bonding. Three important types of bonding arise from the outermost electrons of the atoms. From the top down in the illustration, we have:

    Covalent bonding, with the electrons held tightly between the parent atoms. The example shown is an adjacent pair of carbon atoms, as in the structure of diamond (#6). Diamond is the hardest known substance; covalent bonding is typically very strong.

    Ionic bonding, with one of the parent atoms having custody of the...

  8. 5 Sodium Chloride
    (pp. 11-11)

    After the diffraction of x-rays by crystals was discovered in 1912, the first crystal structure to be deciphered was sodium chloride, table salt. Most chemists expected that molecules containing one sodium atom attached to one chlorine atom would make up the structure. No such luck. Molecules were nowhere to be seen. Instead there was a three-dimensional checkerboard of sodium ions (shown in white on the facing page) alternating with chloride ions (shown in green). In the illustration, sodium ions and chloride ions are shown dissolved in salt brine surrounding the crystal. Again, molecules of sodium chloride are not present.


  9. 6 Diamond
    (pp. 13-15)

    The crystal structure of diamond was investigated early, in the same year as sodium chloride. Each carbon atom has four covalent bonds attached to its nearest neighbors in a cubic array. Because of the strength of the covalent bonds, diamond is the hardest known substance. In a sense, a diamond crystal is one big molecule. Synthetic diamonds, as well as natural diamonds that are not clear enough to use as gemstones, play an important industrial role as abrasives and as cutting tools. For instance, oil-well drill bits faced with diamond have cut wells as deep as 22,000 feet without the...

  10. 7 Hexagonal Diamond
    (pp. 17-17)

    A structure quite similar to natural cubic diamond packs the carbon atoms in a hexagonal array instead of a cubic arrangement. In nature, the hexagonal carbon arrangement has been found in the debris from large meteorite impacts, but nowhere else.

    A number of other crystals, natural and synthetic, can exist in either hexagonal or cubic form. One notable example is zinc sulfide, which is the cubic mineral sphalerite and the hexagonal mineral wurtzite. Some sphalerite crystals have stepped faces where the crystals grew the wurzite structure for a while then jumped back to the cubic sphalerite arrangement. The distinction between...

  11. 8 Nanotubes and Buckyballs
    (pp. 19-19)

    Two forms of carbon, diamond and graphite, have been used since ancient times. It was not until 1985 that the ball-shaped and tubular forms of carbon were produced. Rick Smalley shared the 1996 Nobel Prize for Chemistry for the discovery of the ball-shaped carbon cage. Smalley and his colleagues named the ballsbuckminsterfullerenein honor of R. Buckminster Fuller, who had used the same geometry for his geodesic domes. The name promptly got shortened tobuckyball.

    Smalley realized that the electrically conducting carbon nanotubes could be used to build lightweight electric power transmission lines. The power lines could be used...

  12. 9 Asbestos
    (pp. 21-23)

    Two different minerals have been used commercially as asbestos. In the illustration, the structure on the left is a particular member of the amphibole family that separates easily into thin fibers. On the right is a member of the serpentine family (chrysotile) whose nano-structure is like a rolled-up carpet. Plenty of other minerals would have good heat resistance and insulating properties, but they do not separate into fibers.

    Beginning in the 1970s, asbestos has been regulated as a hazardous substance. If the two varieties of commercial asbestos are such different minerals, would we expect both of them to be equally...

  13. 10 Pyroxene
    (pp. 25-25)

    Crystals of the common rock-forming mineral pyroxene are made up of chains of silicon and oxygen atoms, spaced a nanometer (10-9meter or 10-7centimeter) apart. I gave this as an exam question:

    Unravel a cube of pyroxene, one centimeter (0.4 inch) on a side into a single chain. Would the chain reach from the White House to:

    The Washington Monument (one kilometer, 10⁵ cm)

    Chicago (1000 kilometers)

    The Moon (300,000 kilometers)

    Jupiter (1,000,000,000 kilometers)

    The correct answer is Jupiter. It’s a dirty exam question because most students do it right but then can’t believe their answer. If the chains...

  14. 11 Amino Acids
    (pp. 27-27)

    In 1944, Edwin Schroedinger published a short book calledWhat Is Life?He observed that something had to carry biological “building instructions” from generation to generation. To make the information stable and reliable, bonds at least as strong as the chemical bonds between atoms would be needed.

    Schroedinger speculated that something like an “aperiodic crystal” would be needed to carry the information. (A periodic structure, one that repeats a simple motif over and over, does not carry much information.) Schroedinger was famous for his contributions to quantum mechanics and his book was widely read.

    The dna structure, developed by James...

  15. 12 Phosphate
    (pp. 29-29)

    The use of the chemical element phosphorous in several vital biological roles comes as a surprise. In virtually all natural environments, phosphorous is tightly bound to four surrounding oxygen ions to form a unit known asphosphate. Phosphate is soluble in seawater (and other natural waters) at the level of only a few parts per million. Why then does it turn up as an important part of biological processes? Was it an accident of history or is there no other way to manage a water-based biology?

    The illustration shows three major biological roles for phosphate, although there are more.


  16. 13 Alpha Helix and Beta Sheet
    (pp. 31-33)

    In eight scientific papers published in 1951, Linus Pauling and his coauthors established the structures now known as thealpha helixand thebeta sheet. These structures are composed of proteins: chains of amino acids. The string of dna instructions can lead only to a linear string of amino acids. Curling that long protein string into a useful structure is a major accomplishment of living systems.

    Pauling’s 1951 insight showed that hydrogen bonds (as in ice, #2) could link the amino acid chain into alpha-helix rods and beta sheets. Hydrogen bonds are not as strong as covalent, ionic, or metallic...

  17. 14 Lysozyme
    (pp. 35-35)

    Enzymes are particular kinds of globular proteins that are the biological equivalents of catalysts in chemistry – something that speeds up a chemical reaction without itself being consumed. Lysozyme is a defensive weapon, made from a chain of 129 amino acids. It cuts a specific chemical bond that occurs on the outside of about half of all bacteria. This enzyme opens, lyses, the bacterial cell wall – hence the name lysozyme. It is the protein with the best determined structure, in part because it crystallizes well and it makes up about 3 percent of the weight of the egg white...

  18. 15 Drugs
    (pp. 37-37)

    Most large biological molecules get broken up in our digestive systems. Some small molecules get through, but minor differences between closely related molecules can result in different effects. We show four pairs of molecules, using our normal color scheme with white hydrogens, red oxygens, blue nitrogens, and black carbons.

    At the top, the caffeine in coffee differs from the major flavor in chocolate only by having one methyl (CH3) group added on the left-hand side.

    Tylenol and aspirin are used for roughly the same purposes, and the molecules are similar but not identical. In detail, aspirin and Tylenol have different...

  19. 16 Hemoglobin
    (pp. 39-41)

    Hemoglobin is the red in our red blood cells. It’s a carrier for oxygen. Although a red blood cell takes only five seconds to go through the lung, it gets fully loaded with oxygen. Oxygen is not the only gas that attaches to hemoglobin; carbon monoxide is hazardous because it attaches strongly to hemoglobin. Some red meats and high-grade tuna are treated with carbon monoxide to enhance the red color. Although it sounds bad, the carbon-monoxide-treated meat is not a health hazard to people.

    Hemoglobinis a compound word. Thehemepart is a molecular ring with an iron atom...

  20. 17 Chlorophyll
    (pp. 43-45)

    Blood circulation has been around for “only” 540 million years, but photosynthesis has been active for about 3 billion years. Photosynthesis uses sunlight, carbon dioxide, and water to produce high-energy carbohydrates (sugars and starches). The very oldest undeformed rocks show signs of photosynthetic activity. My generation of geologists was taught that there were essentially no signs of life more than 540 million years old. When I was teaching at the University of Minnesota during the 1960s, there were some handsome rock specimens around showing photosynthetic colonies 2 billion years old; that was not supposed to happen. We finally brought in...

  21. 18 Urease
    (pp. 47-49)

    Before 1828, an absolute barrier was thought to exist between the chemicals produced by living organisms and “inorganic” chemicals produced in the lab. Vitalism was thought to be unique to living systems. That barrier was broken by Friedrich Wohler, who produced urea in his lab from inorganic chemicals. Urea was named, obviously, from urine. Most of the protein nitrogen in the adult diet winds up as urea in the urine.

    A few billion years before 1828, bacteria developed a method for running the urea synthesis backward: converting urea into carbon dioxide and nitrogen-containing ammonia. The bacterial reaction was speeded up...

  22. 19 Lipid Membrane
    (pp. 51-51)

    The outer cell walls of simple single-cell organisms typically consist of a double layer. The building blocks of the layer are calledlipids, which consist of a water-loving glycerine component on one end and two or three waterhating hydrocarbon chains attached. All biologically produced oils, fats, and waxes are lipids. You have lipids coming out your ears. The illustration shows a segment from a bacterial cell wall with the glycerine endings both on the outside (above) and on the inside (below). Longer hydrocarbon chains make the cell wall an even tighter seal against chemical transport.

    Glycerine, more properly called glycerol,...

  23. 20 Rod Virus
    (pp. 53-55)

    A virus, by itself, has no metabolism and cannot reproduce. They function only by invading intact living cells – from bacteria to humans – and by commandeering the cell’s machinery and materials to churn out copies of the original virus. Viruses are a kind of mobile parasite. A chicken is just an egg’s way of making another egg. To a common-cold rhinovirus, I’m just a way of creating another rhinovirus.

    In that sense, viruses are a huge success. There are lots of individual virus particles floating around, and there exists a gigantic diversity of different kinds of virus. Recent analyses...

  24. 21 Icosahedra Virus
    (pp. 57-57)

    Icosahedral viruses include thousands of different types. The icosahedron was known to the ancient Greeks: a solid bounded by twenty equilateral triangles. The icosahedron was used by Buckminster Fuller in his geodesic domes, it occurs as carbon buckyballs, it is the geometry of older soccer balls. Early nuclear weapons made use of the symmetry.

    In the illustration, Stephen has included white lines to emphasize the symmetry. (Real viruses do not have an aluminum tube framework.) The colors serve to identify individual capsid proteins on the surface; the genetic material is protected inside. The structure of one of the capsid units...

  25. 22 Unit Cell Discovery
    (pp. 59-61)

    This is one of those legends that are probably true, but even if it isn’t factual it ought to be true. Around the year 1800, Rene Just Haüy owned an extensive assortment of calcite crystals (calcium carbonate, CaCO3). Haüy accidentally dropped a friend’s calcite crystal and it shattered into small twinkly pieces. He recognized that the shattered pieces had the same shape as a particular calcite crystal that he had at home. Haüy went home and smashed his entire calcite collection; all of them broke into the same-shaped pieces as his friend’s crystal.

    Haüy inferred that the shattered pieces were...

  26. 23 Twinned Crystals
    (pp. 63-65)

    A crystal twin adds a symmetry element that is not present in either half of the twin. Most twins can be described by a rotation of 180 degrees about an axis. (Although a mirror plane might seem to be an exception, a mirror plane is a rotation of 180 degrees plus a center of symmetry.) The 180-degree axis of rotation is shown in the illustration for each of the three twinned crystals. Twins are described in several categories. A contact twin has an obvious planar boundary between the twinned segments, as in the spinel twin. In contrast, the fluorite and...

  27. 24 Calcite Twinning
    (pp. 67-67)

    We felt that a twinning experiment on a natural crystal, at room temperature, would remove a little of the mystery from twinning. It seems less exotic if you can do it on a tabletop, powered by your fingers.

    The experiment begins with a cleavage fragment from a calcite crystal. Calcite is calcium carbonate. (A different structure, also made of calcium carbonate, is calledaragonite, named for the province that brought you Catherine of Aragon.) Calcite is found in antacid pills, ornamental stone (including marble), and kitchen scouring powder. About half of all seashells are calcite; most of the rest are...

  28. 25 Calcite Twin Plane
    (pp. 69-69)

    Twinning a calcite crystal with your fingers is possible because you do not have to flip over all the atoms at once; you can do it one atom at a time. This is a cross section through a twinned calcite crystal. The twin plane is marked by a thin black line halfway down the page.

    Below the twin plane is the original calcite crystal, with red oxygen ions and white calcium ions. The groups of three oxygen ions, tightly bound to a small carbon ion at the center, are calledcarbonategroups. Above the twin plane, the oxygen ions are...

  29. 26 Dolomite Twin Plane
    (pp. 71-73)

    Warning: The facing illustration shows what does not happen. It shows dolomite in the same view as the preceding calcite example, but the twinning is impossible.

    Dolomite, as shown below the impossible twin plane, is similar to calcite but with alternating layers of calcium (white) and magnesium (green) between the carbonate layers (red). Above the suggested twin plane, flipping the carbonate groups over places calcium and magnesium atoms alternating within the same layer. Above the purported twin plane, the crystal is no longer dolomite (see p. 131). The twinning of calcite, as shown in the previous section, is forbidden in...

  30. 27 Quartz
    (pp. 77-79)

    Quartz gets around, from beach sand to wristwatches. From it we derive the silicon for computer chips and the silicone for plastics. Although quartz is silicon dioxide (SiO2), there are many different ways of arranging silicon dioxide into solid crystalline structures. Quartz is one of the least-symmetrical structures allowed in the hexagonal system, but it’s a winner. It is the most stable form of silicon dioxide at room temperature and pressure. (If the namequartzlooks a little odd, it’s because it’s a medieval miner’s word.)

    The crystal structure of quartz lacks a center of symmetry. Some crystals like this...

  31. 28 Close-Packed Metals
    (pp. 81-81)

    Many, but not all, simple metals arrange their atoms in closely packed structures, with each metal atom surrounded by twelve neighbors. However, there are two ways to achieve close packing, shown here by magnesium (above) and by gold (below).

    If you look at the illustration for gold, three possible locations for the atoms are labeled (on the left) as a, b, and c. Reading into the page, the sequence is abcabcabc … and so on. For magnesium, the same three locations are labeled, but atoms appear only at a and b, and the c location is vacant. The vacancy does...

  32. 29 Screw Dislocation
    (pp. 83-83)

    A considerable energy barrier usually must be surmounted in starting a new crystal. A crystal a few atoms across is unstable; somehow the system has to produce a nucleus of several thousand atoms before the crystal can grow. But this is not a rare occurrence – on some days water vapor trails from airplanes grow into cloud streams much larger than the original vapor trail.

    A similar, but smaller, barrier should exist when a growing crystal completes one unit-cell layer and needs to start the next layer. However, some crystals seem to need no energy at all to initiate new...

  33. 30 Erionite
    (pp. 85-85)

    From 1898 to 1956, the only known sample of the mineral erionite was a single specimen in the Harvard mineral collection. As a graduate student studying sediments in several Nevada basins, I found volcanic ash beds altered to several different minerals of the zeolite family. One of them I could not match to any obvious mineral, and the U.S. Geological Survey helped by saying that my x-ray diffraction data seemed to match the Harvard erionite specimen. The Harvard museum was kind enough to send me a small sample from the original erionite specimen, and it matched exactly to my unknown...

  34. 31 Faujasite
    (pp. 87-89)

    A catalyst speeds up a chemical reaction without itself being consumed. A good catalyst is similar to having the right ski wax; you slide downhill faster. However, no ski wax allows you to stand still and slide uphill. In chemistry, “downhill” is a combination of two things: 1) The inherent energy in each molecule, formally called theGibbs free energy, and 2) the relative abundance of each type of molecule.

    Platinum metal is a favorite catalyst, and accordingly industrial users have pushed platinum to twice the price of gold. If you use even tiny crumbs of platinum metal as a...

  35. 32 Lubricants
    (pp. 91-91)

    Several minerals are used as lubricants. All of them have strong sheetlike crystal structures with weak bonds between the sheets. The weak bonds between the sheets are more a matter of physics than of chemistry. Most scientists usevan der Waals forceas sort of a wastebasket term for several different forces – attractive and repulsive – between nearby atoms. The weak bonding allows the sheets to slide past one another and the crystalline material can be used as a lubricant.

    At the top of the illustration is the structure of molybdenum sulfide, MoS2. It is the mineral molybdenite and...

  36. 33 Montmorillonite
    (pp. 93-93)

    Clayis a term used by geologists for the components of any extremely fine-grained sediment. Montmorillonite is a member of a subgroup of clay minerals that are properly calledsmectite. Unfortunately,smectitesounds like a dirty word; most geologists informally usemontmorilloniteas a name for the whole subgroup.

    Montmorillonite, like the mica group (#29) and talc (#32), is composed of sheets. In montmorillonite, the sheets are bonded together by sodium or calcium, as shown in the bottom two layers of the illustration. (Oxygen is red, silicon is yellow, and aluminum has a reflective metallic treatment.) Water molecules can invade...

  37. 34 Perovskite Morph
    (pp. 95-95)

    In 1839, a new mineral was discovered in the Ural Mountains and named after a Russian mineralogist with the impressive name of Count Lev Aleksevitch von Perovski. For the next 140 years, perovskite had an obscure role as a minor rock-forming mineral. It was calcium titanate, CaTiO3. Then, in the 1980s, perovskite emerged as a rock star.

    Perovskite had two new, and newsworthy, roles:

    At high pressure, magnesium silicate (MgSiO3) abandons its low-pressure pyroxene structure (#10) and dresses up in perovskite’s structure. Earth’s mantle deeper than 600 kilometers is inferred to be mostly magnesium silicate perovskite, making it the most...

  38. 35 Perovskite Superconductor
    (pp. 97-97)

    The illustration on the facing page shows the full structure of the ytrrium-barium-copper-oxygen superconductor (YBa2Cu3O7). At the top, middle, and bottom of the illustration are layers identified by the yellow yttrium atoms, accompanied by oxygen vacancies along the vertical cell edges. These divide the original cubic structure into a stack of nano-sandwiches. It is widely thought that the division into layers plays an important role in the superconducting behavior, but the mechanism is not fully understood. (“Not fully understood” is nerdish for “We haven’t the foggiest idea how it works.”)

    The discovery of high-temperature superconductors was a real surprise. All...

  39. 36 Silicon Diode
    (pp. 99-99)

    The simplest semiconductor device in this Age of Silicon is the diode. Somewhat incorrectly, a diode is called “a one-way valve for electricity.” It is sometimes written that a diode “doesn’t obey Ohm’s law.” Ohm’s law says that the electric current through a resistor is a linear function of the voltage. I prefer to say that silicon diodes do obey Ohm’s linear law, but they are cleverly arranged to go nonlinear for voltages much smaller than one volt.

    The illustration shows the inside of a junction diode, made from silicon. The silicon in the right half of both illustrations has...

  40. 37 Fuel Cell
    (pp. 101-101)

    A fuel cell is a chemist’s sweet dream and an engineer’s nightmare. Our illustration shows the chemist’s view. Although the fuel cell was discovered in 1839, the first important application of fuel cells came between 1969 and 1972. The Apollo moon missions used fuel cells to supply electric power and drinking water for the crew. (The near-disaster on the Apollo 13 mission was not from the fuel cell itself; it was from a heater in the liquid-oxygen tank.) The core of a fuel cell consists of a container of liquid divided into two halves by a plastic membrane. On either...

  41. 38 Laser Crystals
    (pp. 103-105)

    Alaser(for “light amplification by stimulated emission of radiation”) is a material that can take in energy from one source and turn out a coherent light beam. The theory behind the laser goes back to Einstein in 1916 and 1917. The first practical gadget, in 1953, amplified microwaves and was called amaser. The race to produce the same effect in visible light was won in 1960 using a synthetic ruby crystal, as shown on the next page. Since then, an enormous range of solids, liquids, and gases has been used in lasers, and they have been powered by...

  42. 39 Supercapacitor
    (pp. 107-107)

    Capacitors, which store electric charge quickly, used to be distinct from batteries, which are slower in taking up and delivering electricity. Recently, several devices in between capacitors and batteries have appeared. This section explains one of those intermediate devices. At the moment, the same system exists under several names: supercapacitors, ultracapacitors, doublelayer capacitors, and even gold capacitors. Structurally, a capacitor consists of two metal sheets separated by an insulating layer. Although it isn’t intuitively obvious, making the insulating layer thinner increases the electrical storage of the capacitor. The size of a capacitor is measured in farads. A one-farad capacitor charged...

  43. 40 Epitaxial Growth
    (pp. 109-109)

    A crystal that takes its orientation from growth on a pre-existing crystal is calledepitaxial. Although inorganic epitaxial crystals occur naturally, they are not at all common. In the organic world, solid structures from seashells to our bones and teeth are controlled by crystal growth on optimized organic substrates. The illustration shows controlled epitaxial growth used to produce blue light-emitting diodes.

    The first synthetic epitaxial material that I remember reading about was in 1945. During World War II, an optical gun sight was produced from large clear natural crystals of calcite. However, optical-quality calcite was in short supply. Sodium nitrate,...

  44. 41 Memristor
    (pp. 111-111)

    In 1971, Leon Chua at U.C. Berkeley pointed out that resistors, capacitors, and inductors (coils) should be joined by a fourth entity, which he named amemristor, but no actual memristors seemed to exist. In 2008, Hewlett-Packard labs announced that they had built working memristors.

    In #36, Silicon Diode, we explained that a diode has a nonlinear behavior because electrons move to create insulating and electrically conducting zones. In contrast, in a memristor whole atoms are moved around to change insulators into conductors. Moving atoms is a blessing and a curse. When the electric power is turned off, the atoms...

  45. 42 Ferromagnetism
    (pp. 113-113)

    More than 1,000 years ago, the Chinese used lodestone (natural magnetite) on a float in a cup of water as the first magnetic compass. That’s the “first” for people; the birds and the bees had used built-in magnetic compasses for millions of years. About 50 different species, from bacteria to migratory animals, can detect Earth’s magnetic field.

    The illustration shows that the crystal structure of magnetite contains iron in two different settings. Iron is magnetic because unpaired electron orbits carry an electrical current, like the current in an electromagnet coil. One location for iron, with four neighboring oxygen ions, is...

  46. 43 Rare Earth Magnets
    (pp. 115-115)

    Around 1980, powerful and relatively inexpensive permanent magnets became available. The new magnets containrare earths, a family of chemical elements (atomic numbers 57 to 71) with useful optical and magnetic properties.

    Rare earths are not exactly “rare.” Neodymium (shown in purple in the illustration) is more abundant than lead in Earth’s crust. Neodymium is the major rare earth in the most successful of the new magnets, which also contain iron (light brown) and boron (dark blue). The magnetic material is produced by mixing the dry powdered ingredients and heating the mixture in an atmosphere-controlled furnace. In the lab, this...

  47. 44 Flash Memory
    (pp. 117-117)

    The modern type of flash drive, first marketed in 1989, has become a ten-billion-dollar-per-year market. Flash memory evolved from the field effect transistor (fet). An fet uses the electric field from one external connection to control the electron flow through semiconductor silicon from a source to a drain. For flash memory, an additional slice of silicon is included between the control and the semiconductor path. This additional slice isn’t electrically connected to anything. (The white spaces in the illustration are electrical insulators.) Normally, the fet and the flash memory use voltages of one to three volts. However, if a twelve-volt...

  48. 45 Metallic Glass
    (pp. 119-119)

    When cooled slowly, virtually all molten substances will solidify into well-ordered crystals. However, for some melts “slowly” can mean more than a year. If cooled rapidly, these slow-to-crystallize substances solidify into a liquidlike disorganized solid. Window glass and camera lenses are familiar examples. Metals crystallize even more rapidly, but in 1957 Sol Duwez at Cal Tech cooled a small splat of molten gold-silicon alloy on a copper plate, precooled with liquid nitrogen, and obtained a disordered metallic glass.

    Commercial production involves squirting molten metal on a rotating chilled drum and peeling off a ribbon of metallic glass partway around the...

  49. 46 Spinodal Decomposition
    (pp. 121-121)

    Almost everyone has used spinodal decomposition: Dissolve powdered Jell-O (thank you again, Kraft Foods) in hot water to make a liquid. Let it cool and it segregates into a weak – but solid – network of gelatin with the water, flavor, and color trapped inside the gelatin network.

    The wordspinodalcomes from a line with a curved bump or hump, a “spine,” on a temperature versus composition graph. Underneath the curved line, a material of mixed composition can separate into regions of different composition. (The decomposition could have been calledbumpodalorhumpodal, butspinodalsounded classier.)

    Although spinodal...

  50. 47 Diamantane
    (pp. 123-123)

    “If life hands you a lemon, make lemonade.”

    — Anonymous

    Pipe carrying natural gas from deep, and hot, wells often gets plugged up by a white crystalline substance. The white substance turns out to be made up of small hydrocarbon molecules that have the same structure as tiny portions of the diamond lattice.

    Deeper than about 15,000 feet (4.5 kilometers) the temperature is high enough to break down crude oil into natural gas. The last surviving oil molecules bear a resemblance either to the structure of graphite or of diamond. The graphitelike molecules are asphalt. The diamondlike structures are the...

  51. 48 Penrose Tiling
    (pp. 125-125)

    The ancient Greek geeks knew that only three regular polygons (with equal sides and angles) could be used to tile a floor: triangles, squares, and hexagons. In addition, there are mixtures. My bathroom floor is tiled with half squares and half octagons. But none of the schemes involved a fivefold symmetry. Classical crystallography, based on repeating patterns, was a mathematically complete theory. Nothing could be added.

    New fivefold nonrepeating tile patterns were introduced in 1973 and 1974 by Roger Penrose, a mathematical physicist. Penrose patented his system and successfully pursued a lawsuit against Kimberly-Clark for embossing a Penrose tiling on...

  52. 49 Penrose Diffraction
    (pp. 127-127)

    Sending a beam of x-rays through an ordinary crystal produces an array of weaker x-ray beams that reflect the symmetry and structure of the crystal. The Penrose tiling on the previous page does not repeat with a regular spacing. Intuitively, the tiling would not be expected to generate a sharp diffraction pattern. To the surprise of the few people who were paying attention, the Penrose tiling and three-dimensional quasicrystals (#50) generated sharp diffraction peaks. However, there was a difference. Ordinary crystals generated an array of x-ray beams with little or no energy between the various beams (#22). The Penrose tiling...

  53. 50 Quasicrystal
    (pp. 129-129)

    Within two years of Laue’s discovery of x-ray diffraction, structures of conventional crystals were being deciphered. Twenty-three years passed from the discovery of quasicrystals to the first determined structure, and even then the structure contains some flexibility for the arrangement of atoms.

    In 2007, Hiroyuki Takaura and his colleagues published a structure for a metallic alloy containing 5.7 cadmium atoms for each atom of ytterbium. (Ytterbium is one of four chemical elements named for the same village in Sweden; there is an unusual geologic deposit next door.) There were several advantages to working with that particular quasicrystal:

    It contained only...

  54. Notes
    (pp. 130-132)
  55. Acknowledgments
    (pp. 133-133)