Why Does Nottingham Heating Occur in Field Emission?

[Benindelft]

Hi,

Can anyone explain exactly why in field emission you get Nottingham heating?

I can understand that you get joule/ resistive heating that makes sense. I can understand that you get cooling, the electron leaves the metal there is a loss of energy.

But why does it matter if it is above or below the Fermi level?

I would have thought that as the electron escapes there is still loss of energy.

next up:
what is then the effect of photo emission / photofield emssion ?


Thanks

Ben

 

[Benindelft]

OK,

I got the answer to my first bit and am pretty sure about the second - but this is an interesting bit of physics so any further discussion would also be fun.

Question was:
Can anyone explain exactly why in field emission you get Nottingham heating?
As I understand it the answer is:
The electron comes from below the Fermi level, it creates a hole which is destroyed by the current flowing. In metal the current carrying electrons have (on average??) the Fermi energy so the net gain in heat energy.

Now for the photon emission (CW)...

The photon excites the electron creating the electron hole pair. If the electron escapes then the hole is replaced by a conduction electron- this results in heating...

Correct?

 

[charng]

jamin

Hi Benjamin,

Nottingham heating, also known as field emission heating, is a phenomenon that occurs when electrons are emitted from a metal surface due to a strong electric field. This type of heating is different from joule/resistive heating, which is caused by the flow of current through a material.

In field emission, the electric field is strong enough to overcome the work function of the metal, which is the minimum amount of energy required for an electron to escape from the metal surface. When the electron is emitted, it carries away some of the energy from the electric field, causing the metal to heat up. This is known as Nottingham heating.

The effect of Nottingham heating depends on the energy level of the emitted electrons. If the electron is emitted from a location above the Fermi level (the highest energy level occupied by electrons in a material), it will have a higher energy and therefore cause more heating. On the other hand, if the electron is emitted from below the Fermi level, it will have less energy and cause less heating.

Photoemission, or photofield emission, is a similar phenomenon in which electrons are emitted from a material due to the absorption of photons. In this case, the photons provide the energy needed to overcome the work function and emit electrons. The effect of photoemission on heating is similar to that of field emission, as the emitted electrons carry away some of the energy from the absorbed photons.

I hope this helps to clarify the concept of Nottingham heating and its relation to the Fermi level. If you have any further questions, please don't hesitate to ask.