204. Final purification of germanium is generally complished by
A. Chemical reactions.
B. Craystal pulling
C. Zone refining
D. Expitaxial growth.

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205. When purification is carried out by melting only a small portion of the sold at a time, the process is called
A. Zone refining
B. Crystal pulling
C. Normal freezing
D. Expitaxial growth

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206. When impurities tend to remain in the liquid rather than the solid, the impurities are
A. impossible to remove by normal freezing.
B. impossible to remove by zone refining.
C. more soluble in the solid than in the liquid.
D. more soluble in the liquid than in the solid.

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207. Germanium
A. has a melting temperature higher than silicon.
B. cannot be purified by the Zonerefining method.
C. is usually purified by the floating-zone method.
D. is more easily purified than silicon.

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208. When no container is used during single-crystal formation, the process is known as
A. boat method
B. ingot method
C. floating-zone methd.
D. normal-freezing method.

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209. One reason silicon is difficult to purify is because
A. its melting temperature is high
B. its melting temperature is low.
C. it will not form single crystals
D. its surface tension is high.

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210. A single crystal is a crystal
A. with no impurities
B. that has cubic shape
C. in which all the elementary cubes have the same orientation.
D. that is made up of only element.

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