A “Bit” About Silicon
by Stephen James O'Meara
The Information Superhighway has been the fast lane to success for many of today's youths. Ask anyone living in Silicon Valley, California (the Beverly Hills of high tech). The Valley cranks out 64 new millionaires every 24 hours. And they all owe their success to grains of sand.
Silicon Valley is the world's center of high technology. Its population of 2.3 million is larger than that of 32 states, and thousands of high-tech companies cram into the 3,900-square-kilometer area—some say, like “transistors on a chip.”
In 1849, this same region was the frontier for America's Gold Rush. Today there is another gold rush going on here, but this one isn't about mining. It's about cyberspace…and about turning silicon into gold! What does silicon have to do with gold and cyberspace? Everything! So let me tell you a “bit” about silicon and how it has changed the way we live.
What Is Silicon? Code name “element 14” in the Periodic Table. Next to the air we breathe, silicon is the most abundant element found in nature. It forms about 28 percent of the Earth's crust; in rocks, silicon is the most abundant element. You walk over countless tons of it each day. Chemically, it is classified with carbon, the element found in all living matter. And, like carbon, silicon has the ability to enter into complicated combinations with other elements. In fact, you just don't find pure silicon on Earth; it's always mixed up with other elements, usually in the form of silicon oxides such as sand, quartz, and rock crystal.
How Do We Get Pure Silicon? The basic building block of materials like sand and quartz is the silicon-oxygen tetrahedron—a geometrical figure having four faces, like a pyramid. A silicon-oxygen tetrahedron is composed of one silicon atom at the center of a pyramid formed by four oxygen atoms. The oxygen atoms are negatively charged, so they attract positively charged atoms to the corners of the pyramid and form bonds. But bonds can be broken. Swedish chemist Jons Jacob Berzelius realized that in 1824 when he became the first to isolate silicon from its oxygen crypt. He did this basically by extracting it from sand under high temperature. Once silicon was extracted, it was used to make cast iron, bricks, pottery—it had all kinds of applications, from manufacturing to art.
How Is Silicon Used in Computers? The first modern computers didn't use silicon. They were horrendously large machines. One wouldn't have fit in your classroom! It consisted of more than 50,000 components. And at the heart of this monster machine were vacuum tubes—an electrical device created during 1911–1913 that looked like a large incandescent light bulb with wires, filaments, and other electrical parts inside. Also inside was a vacuum (which allowed electrons to move freely without interaction with other gases)—hence the name of the tube. An early computer used as many as 18,000 vacuum tubes! The tubes were big, brittle, hot as an oven, and quick to burn out (every few minutes). As one AT&T researcher said, “Nature abhors the vacuum tube.”
Did Silicon Replace Vacuum Tubes? Yes! And it did so in the form of a transistor. A transistor is an electronic device like the vacuum tube, but it is solid, smaller, cooler, and more reliable. Transistors use much less power than vacuum tubes and have a much longer life. This development alone was responsible for the improved machines called second-generation computers. Today, millions of tiny transistors with interconnecting wires can fit on a wafer-thin slice of silicon the size of your fingernail. This electronic city on a “chip” is called an integrated circuit. In time, integrated circuits were used not only to control the “brains” of a computer, but also its memory. An integrated circuit that controls computer memory is called a “memory chip.”
But Why Silicon? Silicon is a semiconductor. That means it can both insulate electric current (like glass) and conduct it (like copper). But if you take silicon in its ultra-pure form, then chemically add small but measured amounts of certain impurities (a process called “doping”), you can alter silicon's atomic structure—in effect, change its electrical charge. By doping silicon, scientists can make it act as either a conductor or an insulator. That's why silicon is called a “semiconductor.” A transistor, then, is nothing but a semiconductor device. It can be used in two ways. Ever hear of a transistor radio? Well in a radio, a transistor amplifies a signal plucked out of the air by an antenna and makes it strong enough to boom out of a speaker. In a computer, however, a transistor is a semiconductor device that acts as an on-off switch to regulate the flow of information—bit by bit.
What's a Bit? A bit is your basic unit of computer information, represented as either a 1 or a 0. Eight bits makes one byte. It takes one byte of information, for example, to tell your computer to execute a command. And the way a chip of silicon is designed (thickness, size, etc.) determines how fast a transistor can toggle back and forth from one bit to another.
Did Silicon Change the Computer Industry? Absolutely! The use of silicon in computers has allowed researchers to devise new ways to make integrated circuits ever smaller, making them much less expensive to build. On the consumer end, integrated circuits brought about the minicomputer revolution, making computers smaller, faster, cheaper, and better. And the trend continues. Today the chips have become so small that the components look like angels dancing on the head of a pin. Computer chips are being used today in everything from space shuttles to coffee makers. If you see a device that's programmable, there's a chip inside. Of course, the most amazing creation is the microprocessor—the world's most sophisticated chip—whose transistors can execute hundreds of millions of instructions per second. A microprocessor is the most complex manufactured product on Earth. How big are the transistors in a microprocessor? About 1/5000 of a millimeter, or about one thousand times smaller than the period at the end of this sentence. It's not too early to start your own dreams about how to use silicon in cyberspace. Who knows, maybe you'll become one of those Silicon Valley millionaires someday! Or will a new Silicon Valley be your own back yard?
- What is a semiconductor?
[anno: A semiconductor is something that can both conduct electricity or insulate a substance conducting electricity.]
- How is silicon treated to alter its electrical charge? What happens when silicon's electrical charge is altered?
[anno: Silicon can be chemically treated with impurities to alter its electrical charge. Altering silicon's electrical charge causes silicon to be either a conductor or an insulator.]
- What is an integrated circuit?
[anno: An integrated circuit consists of millions of transistors with interconnecting wires.]
- Where else could you find a structure that operates like an integrated circuit? Think of an example of something that functions like an integrated circuit. Write a few sentences that describe how that structure functions in the same way.
[anno: Answers may vary but could include that the human brain is like an integrated circuit. The neurons act as transistors passing information from one part of the brain to others and then out into the body.]