Measurement of energy gap of a thermistor
Objectives:
1. To measure the temperature dependence of the resistance of a thermistor
2. To determine the energy gap in the semiconductor material
Introduction:
Absorption of energy by the semiconductor can boost electrons from the valence band to the conduction band. The amount of energy is at least as large as the energy gap (Eg). Ideally, the conduction band is completely emptyat T= 0 K. As the temperature is raised, some electrons get enough energy to "pop up" into the conduction band, in accordance with statistical physics. Therefore, higher energy states can be populated be electrons due to thermal excitation.
Electrical current is defined form the movement of electric charge. Thus, electrons in the conduction band are able to move from atom to atom, and so contribute to electric currents. An unoccupied state in the valence band is called a hole; electrons in the valence band can contribute to electric currents by moving to fill the hole states. When this happens it is easy to visualize a hole moving opposite the direction an electron moves in the valence band, and so this is referred to as hole conduction
For a particular material, the higher the temperature, the more charges (electrons in the conduction band and holes in the valence band) are available to move through the solid.The relationship between the resistance R (which is proportional to resistivity) of the material can be written as a function of temperature
Measurement of energy gap of a thermistorObjectives:1. To measure the temperature dependence of the resistance of a thermistor2. To determine the energy gap in the semiconductor material Introduction:Absorption of energy by the semiconductor can boost electrons from the valence band to the conduction band. The amount of energy is at least as large as the energy gap (Eg). Ideally, the conduction band is completely emptyat T= 0 K. As the temperature is raised, some electrons get enough energy to "pop up" into the conduction band, in accordance with statistical physics. Therefore, higher energy states can be populated be electrons due to thermal excitation.Electrical current is defined form the movement of electric charge. Thus, electrons in the conduction band are able to move from atom to atom, and so contribute to electric currents. An unoccupied state in the valence band is called a hole; electrons in the valence band can contribute to electric currents by moving to fill the hole states. When this happens it is easy to visualize a hole moving opposite the direction an electron moves in the valence band, and so this is referred to as hole conductionFor a particular material, the higher the temperature, the more charges (electrons in the conduction band and holes in the valence band) are available to move through the solid.The relationship between the resistance R (which is proportional to resistivity) of the material can be written as a function of temperature
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