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293:) is a group of similar methods of purifying crystals, in which a narrow region of a crystal is melted, and this molten zone is moved along the crystal. The molten region melts impure solid at its forward edge and leaves a wake of purer material solidified behind it as it moves through the ingot. The impurities concentrate in the melt, and are moved to one end of the ingot. Zone refining was invented by
382:
through a thin section of furnace very slowly, such that only a small region of the boule is molten at any time, the impurities will be segregated at the end of the crystal. Because of the lack of impurities in the leftover regions which solidify, the boule can grow as a perfect
455:
are used extensively in research facilities particularly for the production of insulators, but their use in industry is limited by the relatively low power of the lamps, which limits the size of crystals produced by this method. Zone melting can be done as a
460:, or it can be done continuously, with fresh impure material being continually added at one end and purer material being removed from the other, with impure zone melt being removed at whatever rate is dictated by the impurity of the feed stock.
414:
is placed in the molten zone, which is passed through the pure germanium. With the proper choice of rate of heating and other variables, the antimony can be spread evenly through the germanium. This technique is also used for the preparation of
378:(the ratio at equilibrium of an impurity in the solid phase to that in the liquid phase) is usually less than one. Therefore, at the solid/liquid boundary, the impurity atoms will diffuse to the liquid region. Thus, by passing a crystal
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1230:, in which two solutes are distributed through a pure metal. This is important in the manufacture of semiconductors, where two solutes of opposite conductivity type are used. For example, in germanium, pentavalent elements of
1162:
325:
system having an appreciable concentration difference between solid and liquid phases at equilibrium. This process is also known as the float zone process, particularly in semiconductor materials processing.
391:
is placed at the base to initiate a chosen direction of crystal growth. When high purity is required, such as in semiconductor industry, the impure end of the boule is cut off, and the refining is repeated.
466:
methods use an induction-heated tungsten ring to heat the ingot radiatively, and are useful when the ingot is of a high-resistivity semiconductor on which classical induction heating is ineffective.
333:
A diagram of the vertical zone refining process used to grow single-crystal ice from an initially polycrystalline material. The convection in the melt is a result of water's density maximum at 4 °C.
83:
1254:
produce positive (p-type) conduction. By melting a portion of such an ingot and slowly refreezing it, solutes in the molten region become distributed to form the desired n-p and p-n junctions.
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A variety of heaters can be used for zone melting, with their most important characteristic being the ability to form short molten zones that move slowly and uniformly through the ingot.
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is the highest among various manufacturing processes. Float-zone carrier lifetimes are around 1000 microseconds compared to 20–200 microseconds with
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In zone refining, solutes are segregated at one end of the ingot in order to purify the remainder, or to concentrate the impurities. In
265:
65:
coil melts a section of the metal bar in the tube. The coil moves slowly down the tube, moving the molten zone to the end of the bar.
1181:, float zone processing is particularly useful because the single-crystal silicon grown has desirable properties. The bulk charge
194:
439:, or gas flames are common methods. Another method is to pass an electric current directly through the ingot while it is in a
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1309:
399:, the objective is to distribute solute evenly throughout the purified material, which may be sought in the form of a single
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224:
497:, the number of impurities in the liquid change. Impurities are incorporated in the melting liquid and freezing solid.
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carefully set to be just equal to the weight in order to hold the liquid suspended. Optical heaters using high-powered
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The number of impurities in the liquid changes in accordance with the expression below during the movement
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939:{\displaystyle \int _{0}^{x}dx=\int _{I_{O}}^{I}{\frac {dI}{C_{O}-{\frac {k_{O}I}{L}}}}}
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single crystal, made by the floating-zone process (cylindrical object in the center)
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410:, an ingot of germanium is first purified by zone refining. Then a small amount of
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1157:{\displaystyle C_{S}(x)=C_{O}\left(1-(1-k_{O})e^{-{\frac {k_{O}x}{L}}}\right)}
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1304:. Crystals. Vol. 12. Berlin, Heidelberg: Springer Berlin Heidelberg.
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Pfann, at left, showing the first zone refining tube, Bell Labs, 1953
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produce negative (n-type) conduction and the trivalent elements of
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578:: initial uniform impurity concentration of the solidified rod
27:
Purification process by moving a molten zone along a metal bar
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404:
607:: concentration of impurities in the liquid melt per length
658:: number of impurities in zone when first formed at bottom
341:
Silicon crystal in the beginning of the growth process
1197:. A longer bulk lifetime increases the efficiency of
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403:. For example, in the preparation of a transistor or
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as a method to prepare high-purity materials, mainly
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374:The principle is that the segregation coefficient
470:Mathematical expression of impurity concentration
1458:
1431:. M. K. Lee (3 ed.). New York, NY: Wiley.
1411:, Michael D. Deal, and Peter B. Griffin (2000)
687:: concentration of impurities in the solid rod
1428:Semiconductor devices: physics and technology
259:
1204:
783:{\displaystyle dI=(C_{O}-k_{O}C_{L})\,dx\;}
1033:
980:
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779:
266:
252:
1213:-based high-power semiconductor devices.
772:
474:When the liquid zone moves by a distance
352:
344:
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328:
14:
1459:
1297:
1388:, Volume 21, W-X-Y-Z, 1973, page 501.
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629:: number of impurities in the liquid
1424:
225:Shaping processes in crystal growth
24:
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1193:, and 1–30 microseconds with cast
369:
313:. Its first commercial use was in
61:Vertical zone refining, 1961. The
25:
1498:
1418:
1342:J. D. Bernal: The Sage of Science
1221:
1037:{\displaystyle C_{S}=k_{O}I/L\;}
81:
43:
34:
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195:Fractional crystallization
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1391:
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1172:
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1062:
984:{\displaystyle I_{O}=C_{O}L\;}
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464:Indirect-heating floating zone
13:
1:
1325:
1287:Hermann Schildknecht (1966),
1339:Brown, Andrew (2005-11-24).
1301:Crystal Growth from the Melt
1209:It's used for production of
215:Laser-heated pedestal growth
7:
1386:The World Book Encyclopedia
1257:
1226:Another related process is
826:{\displaystyle C_{L}=I/L\;}
205:Hydrothermal synthesis
170:Bridgman–Stockbarger method
10:
1503:
1266:a.k.a. freeze distillation
426:
1482:Methods of crystal growth
1415:, Prentice Hall, page 129
1398:Float Zone Crystal Growth
1384:”Zone melting”, entry in
1293:, Weinheim: Verlag Chemie
527:: segregation coefficient
297:and further developed by
247:
175:Van Arkel–de Boer process
161:
156:
120:
115:
94:
89:
80:
73:
1205:High-resistivity devices
200:Fractional freezing
1477:Liquid-solid separation
1413:Silicon VLSI Technology
1270:Monocrystalline silicon
1195:polycrystalline silicon
349:Growing silicon crystal
291:floating-zone technique
180:Czochralski method
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157:Methods and technology
1374:John Wiley & Sons
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682:
680:{\displaystyle C_{S}}
653:
651:{\displaystyle I_{O}}
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600:{\displaystyle C_{L}}
573:
571:{\displaystyle C_{O}}
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522:
520:{\displaystyle k_{O}}
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443:, with the resulting
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1487:Semiconductor growth
1472:Industrial processes
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309:, for manufacturing
287:floating-zone method
1425:Sze, S. M. (2012).
1298:MĂĽller, G. (1988).
1275:Wafer (electronics)
1264:Fractional freezing
886:
855:
714:of the molten zone
445:magnetomotive force
421:integrated circuits
295:John Desmond Bernal
149:Single crystal
129:Crystal growth
1211:float-zone silicon
1191:Czochralski method
1187:float-zone silicon
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707:{\displaystyle dx}
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490:{\displaystyle dx}
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437:resistance heaters
367:
351:
343:
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220:Micro-pulling-down
1438:978-0-470-53794-7
1311:978-3-642-73210-2
1217:Related processes
1145:
934:
931:
622:{\displaystyle I}
542:{\displaystyle L}
276:
275:
210:Kyropoulos method
139:Seed crystal
134:Recrystallization
103:Crystal structure
63:induction heating
16:(Redirected from
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1409:James D. Plummer
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1366:William G. Pfann
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1281:Further reading
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433:Induction coils
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370:Process details
357:A high-purity (
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235:Verneuil method
124:Crystallization
75:Crystallization
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1345:. OUP Oxford.
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549:: zone length
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458:batch process
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1370:Zone Melting
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1315:. Retrieved
1300:
1290:Zone Melting
1289:
1227:
1225:
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1176:
1168:Applications
690:
473:
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396:
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389:seed crystal
375:
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290:
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279:Zone melting
278:
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240:Zone melting
239:
90:Fundamentals
58:
53:
1199:solar cells
1179:solar cells
1173:Solar cells
453:xenon lamps
423:("chips").
419:for use in
311:transistors
190:Flux method
1461:Categories
1326:References
1317:2023-11-23
108:Nucleation
1447:869833419
1248:aluminium
1244:group III
1123:−
1102:−
1093:−
909:−
867:∫
843:∫
747:−
315:germanium
303:Bell Labs
1467:Crystals
1258:See also
1246:such as
1236:antimony
1234:such as
412:antimony
363:tantalum
116:Concepts
1368:(1966)
1240:arsenic
1232:group V
449:halogen
427:Heaters
417:silicon
401:crystal
323:solvent
185:Epitaxy
98:Crystal
59:(right)
1445:
1435:
1349:
1308:
319:solute
165:Boules
54:(left)
1252:boron
405:diode
387:if a
380:boule
289:, or
285:, or
1443:OCLC
1433:ISBN
1347:ISBN
1306:ISBN
1250:and
1238:and
281:(or
1185:in
1177:In
451:or
301:in
1463::
1441:.
361:)
359:5N
1449:.
1355:.
1320:.
1151:)
1143:L
1139:x
1134:O
1130:k
1119:e
1115:)
1110:O
1106:k
1099:1
1096:(
1090:1
1086:(
1080:O
1076:C
1072:=
1069:)
1066:x
1063:(
1058:S
1054:C
1031:L
1027:/
1023:I
1018:O
1014:k
1010:=
1005:S
1001:C
978:L
973:O
969:C
965:=
960:O
956:I
929:L
925:I
920:O
916:k
904:O
900:C
894:I
891:d
883:I
876:O
872:I
863:=
860:x
857:d
852:x
847:0
820:L
816:/
812:I
809:=
804:L
800:C
777:x
774:d
770:)
765:L
761:C
755:O
751:k
742:O
738:C
734:(
731:=
728:I
725:d
702:x
699:d
673:S
669:C
644:O
640:I
617:I
593:L
589:C
564:O
560:C
537:L
513:O
509:k
485:x
482:d
376:k
321:–
267:e
260:t
253:v
20:)
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