Imperfections In Solids Semiconductors

The appearance of colour in solid alkali metal halides is generally due to:

1. F-centres.

2. Schottky defect.

3. Frenkel defect.

4. Interstitial positions.

Silicon gives p-type of semiconductor on doping with:

1. Germanium.

2. Arsenic.

3. Selenium.

4. Boron.

The correct statement regarding defects in a crystalline solid is:

1.	Schottky defects have no effect on the density of crystalline solids.
2.	Frenkel defects decrease the density of crystalline solids.
3.	Frenkel defect is a dislocation defect.
4.	Frenkel defect is found in halides of alkaline metals.

The incorrect statement among the following is -

1.	Density decreases in case of crystals with Schottky's defect.
2.	NaCl(s) is insulator, silicon is semiconductor, silver is conductor, quartz is piezo electric crystal.
3.	Frenkel defect is favoured in those ionic compounds in which sizes of cations and anions have large difference.
4.	has non stoichiometric metal excess defect.

A compounds that can show both, Frenkel as well as Schottky defects is -

1. AgBr

2. AgI

3. NaCl

4. ZnS

Select the correct option based on statements below:

Assertion (A):	In a particular point defect, an ionic solid is electrically neutral, even if few of its cations are missing from its unit cells.
Reason (R):	In an ionic solid, Frenkel defect arises due to dislocation of cation from its lattice site to interstitial site, maintaining overall electrical neutrality.

1.	(A) is false but (R) is true.
2.	Both (A) and (R) are true and (R) is the correct explanation of (A).
3.	Both (A) and (R) are true but (R) is not the correct explanation of (A).
4.	(A) is true but (R) is false.