Silicon and Germanium

HISTORICAL NOTE tons, as well as body tissues and fluids. It is never found in the free state, however, but Silicon and Germanium most often as a compound with oxygen In the late 1940s, two elements—silicon tories ushered in a revolution in electronics (SiO2) called silica; 95% of the earth's rocks and germanium—suddenly received a that continues today in the rapid advances contain silica as their principal component. surge in interest due to the discovery of in solid-state devices, integrated circuits, Germanium, on the other hand, is a very their ability to act as "semiconductors," and miniaturized electronic components. rare element, comprising only about i.e., to conduct electricity more efficiently Both silicon and germanium were recog- 0.0005% of the earth's crust; making recov- than an insulator (such as rubber) but less nized as elements long before their uses as ery difficult, too, is the fact that germa- efficiently than a conductor (such as cop- semiconductors were even imagined. Sili- nium is not found in natural con- per). The invention of the semiconductor con is the second most abundant element centrations or deposits, but rather is evenly device called the transistor in 1947 by John in the earth's crust (second only to oxy- distributed in trace quantities in many Bardeen, Walter H. Brattain, and William gen), and is found in almost every rock, all rocks. Like silicon, germanium is never B. Shockley at the Bell Telephone Labora- natural water, plants, and animal skele- found in the free state, but always in various uncommon minerals and sulfide ores, especially those of silver, lead, tin, zinc, and antimony. Until the late 18th century, chemists Custom Silicon Micromachining were not able to separate elemental silicon from its silica compound; some chemists > Micromachined Silicon Structures even considered silica itself to be a pure element. In 1787, A. Lavoisier in France spec- ulated that silica was probably the oxide of • Silicon Membranes an as-yet-undiscovered element. Various chemists attempted to isolate the element, • Anodic Bonding A A A including Sir Humphry Davy in England in 1800, and Louis Thenard and Joseph Gay-Lussac in 1811, but their results were • Applications include: not conclusive. In 1817, a chemist in Swe- den, Jons Jakob Berzelius, discovered that - Sensor Structures A A A the element was present without oxygen inside cast iron; in 1823 Berzelius finally 400 microns succeeded in establishing the existence of - X-ray lithography silicon as an element, though he could pre- pare only an impure form. Silicon was finally created in reproduc- - Soft x-ray windows and optics ible crystalline form in 1854—nearly 70 years after its existence had first been • Design and Consulting Services proposed—when Henri Saint-Claire Deville crystallized it out of an alloy he pro- duced by mixing melts of chlorides and For more information contact us! then electrolyzing them. He named the el- Micro-Optics Technologies, Inc. ement silicon (loosely) after the Latin word for flint, "silex." 8608 University Green #5 In 1871, a chemist in Russia, Dmitri Middleton, Wl 53562 Ivanovich Mendeleev, predicted a hypo- (608) 831 -0655 FAX (608) 831 -5821 thetical element in group IVA of the Peri- odic Table between silicon and tin, Internet: 72360.2261 (©CompuServe. Com describing its expected physical properties and naming it tentatively "eka-silicon." Fif- Circle No. 51 on Reader Service Card. teen years later, in 1886, Clemens Winkler analyzed argyrodite, a sulfide mineral, and found a previously unknown constituent; he isolated it and named it "germanium" SPECIAL NOTICE TO MRS MEMBERS: after his native country of Germany. Fur- ther investigation by other chemists con- 1993 Members of the Materials Research Society may subscribe to MATERIALS firmed its position between silicon and tin LETTERS for the special rate of $38. You will receive Volumes 15,16,17 and 18. in group IVA in the periodic table, just as MATERIALS LETTERS is an interdisciplinary journal affiliated with the Materials Mendeleev had predicted. Research Society, devoted to the rapid publication of short communications on the Germanium is a hard, silvery-gray solid science, applications and processing of materials. with a metallic appearance. It is brittle Order your subscription today from: Materials Research Society, 9800 McKnight rather than ductile, with the arrangement Road, Pittsburgh, PA 15237 • Phone: (412) 367-3003; FAX (412) 367-4373 of atoms in its crystalline structure similar to the diamond lattice of carbon. Before its Downloaded96 from https://www.cambridge.org/core. IP address: 170.106.202.8, on 01 Oct 2021 at 06:45:08, subject to the Cambridge Core terms of use, availableMRS BULLETIN/MARC at H 1993 https://www.cambridge.org/core/terms. https://doi.org/10.1557/S0883769400044055 MIT OFFICE New Laser Particle Size of the Distribution Analyzer SUMMER SESSION presents Electro-Ceramics: Properties and Applications July 19-21, 1993 Solid State Sensors, Batteries and Fuel Cells July 19-21, 1993 Fiber Reinforced Composite LA-900 Materials .04-1020 |im in single analysis July 26-30, 1993 PC controlled for versatile operation Operated under Windows 3.0 for flexible For further information on this and other programs, please contact: Prof. F. J. McGarry, Director, MIT Office of the data display Summer Session, E19-356, Cambridge MA 02139-307. Phone: 617-253-2101. Fax: 617-253-8042. 30 second analysis, start to finish Circle No. 53 on Reader Service Card. 17671 Armstrong Avenue, Irvine, California 92714 Phone: 1 (800) 4-HORIBA, FAX (714) 250-0924 Circle No. 52 on Reader Service Card. HISTORICAL NOTE use in the semiconductor industry, germa- States by Edward G. Achison. Until the Germanium semiconductor devices re- nium had little commercial importance. It creation of boron carbide in 1929, silicon placed many of the vacuum tubes, diodes, was used only in an alloy (with gold) for carbide was the hardest synthetic material and rectifiers normally used in common dental work, and in glass, for infrared opti- known. electronic devices, and also performed cal devices such as lenses, prisms, and Silicon is also the starting material for the new functions that vacuum tubes could windows. organic-compound silicones used as plas- not handle. Since 1948, there have been Like germanium, crystalline silicon is tics, oils, greases, and synthetic rubbers. many developments in the industry, for also a brittle solid, and is black to dark gray Inorganic silicon compounds are used in example, the diffused-junction transistor. in appearance, with a high metallic luster. the manufacture of glass and ceramics, pi- During the 1960s, elemental silicon sup- Elemental silicon is dark brown in its amor- ezoelectric crystals, and insulating materi- planted germanium as the most common phous form. Unlike germanium, elemen- als. semiconductor material. Heating silica tal silicon had found many commercial Toward the end of World War II, new with coke in an electric furnace yields ele- applications by the turn of the century. Sili- processing methods made available large mental silicon of ordinary purity, but "zone con is used as an alloying ingredient to quantities of extraordinarily pure germa- refining" yields silicon of a much higher strengthen magnesium, aluminum, and nium, opening the door to its use in the purity, suitable for electronics. Silicon has copper. Mixing silicon with tin and copper electronics industry. Highly pure germa- several advantages over germanium, in makes silicon bronze, which found wide nium ingots are remelted and doped with that it is vastly more common than germa- use in telephone and telegraph wires. Fer- specific impurities (such as arsenic or gal- nium and is thus intrinsically less expen- rosilicon is used in making very resistant lium) to produce desired electronic charac- sive; silicon also retains its semiconducting silicon steels. teristics. After about 1945, germanium's properties at higher temperatures. Silicon Silicon carbide (also known by the trade properties as a semiconductor became forms an oxide film with excellent electrical name Carborundum) is an exceedingly widely known. The first transistor was an- insulating properties; the film can be used hard, clear, green-tinged crystalline com- nounced in 1947, and a year later the ger- as a mask to permit the introduction of spe- pound first created in 1891 in the United manium triode was put on the market. cific impurities needed for doping the DownloadedMRS BULLETIN/MARC from https://www.cambridge.org/coreH 1993 . IP address: 170.106.202.8, on 01 Oct 2021 at 06:45:08, subject to the Cambridge Core terms of use, available at 97 https://www.cambridge.org/core/terms. https://doi.org/10.1557/S0883769400044055 INSTITUTE OF PHYSICS PUBLISHING NEW MANUFACTURING PROCESSES AND MATERIALS SERIES NEW AND RECENT TITLES ADVANCED WELDING PROCESSES NEW J Norrish, Cranfield Institute of Technology, UK This textbook covers principle features and applications, including MORE TITLES OF INTEREST power source technology, filler materials, gases for advanced welding, narrow gap techniques and automation. Invaluable to ARTJflCE AND ARTEFACTS NKW__ engineers in manufacturing industry. 100 Essays in Materials Science 1992 392 pages illus hard 0 85274 325 4 $140.00 RWCahn, University of Cambridge, UK paper 0 85274 326 2 $49.50 An entertaining collection of scientific journalism and book reviews selected by the Materials Science correspondent of Nature, this book POWDER METALLURGY covers many different topics and will appeal to a wide range of The Process and its Products scientists. A G Dowson 1992 384 pages illus hard 0 7503 0152 X $39.90 'An excellent, clearly written expose on essentially all the sub-processes in PM.' PHYSICS OF NANOSTRUCTURES TEXT International Journal of Powder Metallurgy Edited by J H Davies and R Ix>ng. University of Glasgow, UK Explains the development of the powder metallurgy process, Prepared for postgraduate students working on nano- and surveying its capabilities for a range of products and discussing the microstructures, this is a collection of contributions from leading potential for future applications.

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