Topics 7 - Fermi surfaces near Brillouin zones

Question 1

Describe an experimental technique that measures conduction band electron
energy distribution in metal and determine Fermi energy

Answer 1

Soft X-ray emission

To measure the energy distributions:
High energy electron bombardment against a sample
It is used to create holes in
one of the inner shells by exciting electrons to very high energy states

Conduction electron
falls into the hole with the resultant X-ray photon emitted

Question 2

Explain how the conduction band electron energy distribution is obtained.

Answer 2

The Intensity distribution of the emitted xrays gives a measure of the conduction electron distribution

Question 3

What does a soft x-ray emission spectrum look like

Answer 3

The intensity of X-ray
emission starts rising at a value corresponding to the electrons from the bottom of the conduction band falling to the inner shells.

At about a certain value there is a sharp fall in the intensity of X-ray emission
down to zero, which corresponds to the recombining Fermi electrons.

The value of the
Fermi energy EF (measured from the bottom of the conduction band)

Most energy is released for the fermi electron