Tag: electrical and magnetic properties of solids

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Multiple choice chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

Doping of $As$ with $Si$ is called :

  1. n-type semi-condutor

  2. p-type semi-conductor

  3. intrinsic semi-conductor

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$As$ is a member of group $V$ and has 5 electrons in its outermost shell. 


When $Si$ is doped with group $V$ elements such as $As$ then, $Si$ forms four bonds with $As$ and one extra electron is left free for conduction. 

Since the conduction is due to the presence of free electrons, therefore, it is known as n-type semiconductor.

Therefore, the option is A.

Multiple choice chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

An n-type semi-conductor is formed when a trace amount of impurity is added to silicon. The number of valence electrons in the impurity atom must be: 

  1. $3$
  2. $5$
  3. $1$
  4. $2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

An n-type semiconductor is due to the presence of a free electron in the semiconductor. Since silicon is an element having $4$ valence electrons, in order to have a free electron, it must be doped with an element having one more valence electron than silicon. 


Hence the number of valence electron in the impurity must be $4+1=5.$

Therefore, option B is correct.

Multiple choice chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

Which of the following statements is correct about the conduction of electricity in pure crystal of silicon at room temperature?

  1. The conduction is due to electrons present in fully occupied lowest energy states.

  2. The conduction is due to only some electrons capable of leaving the bonds at room temperature.

  3. The conduction is only due to the holes formed from the release of electrons.

  4. The conduction is due to the movement of both the electrons released and holes formed.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In semiconductor two types of the semiconductor are present. They are an intrinsic and extrinsic semiconductor. A pure silicon crystal is an example of an intrinsic semiconductor. 

The conduction in the intrinsic semiconductor is due to the moving of electrons from valence bond to conduction bond by means of thermal energy. Due to the thermal energy the $Si-Si$ bond breaks and creates electron deficiency which is also called a hole. So, both the holes and electrons released to account for the conduction of electricity.

Multiple choice chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

p type semi conductor is formed when trace amount of impurity is added to silicon. The number of valence electrons in the impurity atom must be:

  1. $3$
  2. $5$
  3. $1$
  4. $2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

To form a p-type semiconductor, one must add elements from boron family to the silicon atom.

Boron family has 3 valance electrons so, number of valance electrons in the impurity atom must be 3.

Multiple choice chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

Addition of arsenic in small amount to pure germanium will result in the formation of

  1. n-type semiconductor

  2. germanium arsenide

  3. p-type semiconductor

  4. a superconducting alloy
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Arsenic is a Group 15 element. Doping Germanium (Group 14) with a Group 15 element provides an extra electron, resulting in an n-type semiconductor.