Question

Elemental silicon to be used as a semiconductor is purified by

• A. heating under vacuum
• B. floatation
• C. zone refining
• D. electrolysis

Hint:

High-purity silicon is required for the semiconductor industry. The needed levels of purity cannot be reached by chemical methods alone.

Answer 1

The Correct Option is C

Zone refining is used for metals that are required in very high purity. Semiconductor silicon is purified by this method.

Semiconductor materials like Si and Ge are usually purified by zone refining. 

So, the correct answer is Option C) Zone refining.

Answer 2

The correct option is (C)

Semiconductor materials like Si and Ge are purified by zone refining which is based on principle of fractional crystallisation. 

Due to differences in the solubilities of impurities in solid and molten states of metal, zones of the impurities are formed and then finally removed.

Answer 3

High-purity silicon is required for the semiconductor industry. The needed levels of purity cannot be reached by chemical methods alone.

• For this, a standard technique is used for purifying semiconductors i.e., the zone refining process. 
• It is a process in which a small rod of impure silicon is passed through a high-temperature furnace. 
• As the rod is heated, the impurities tend to move toward one end of the rod, leaving the other end more pure.

A narrow zone of the rod is then melted using a heat source, and the molten zone is moved slowly along the length of the rod. This process causes the impurities to be concentrated in the melted zone and moved to one end of the rod.

• The process is repeated several times, each time causing the impurities to be further concentrated in one end of the rod. 
• After multiple passes, the impurities are concentrated in a small region of the rod, which can then be cut off and discarded. 
• The remaining pure silicon rod can be used as a semiconductor material.

In summary, zone refining is a process used to purify elemental silicon by passing it through a high-temperature furnace and repeatedly melting and moving a narrow zone along the length of the rod. This process concentrates impurities at one end of the rod, leaving a highly pure silicon material for use as a semiconductor.
Elemental silicon to be used as a semiconductor is purified by zone refining.