Amorphous materials

OJL interband transition model for amorphous materials - a brief tutorial

From order to disorder

Electronic interband transitions excited by light absorption in amorphous materials dominate the optical properties in the near infrared, visible and UV. Due to the missing long range order no k-selection rule holds and almost all matrix elements are different from zero. Hence the pronounced van Hove singularities being characteristic for a certain crystalline material are not as pronounced any more in the corresponding amorphous case. An example is given in the graphs below where the dielectric function of crystalline (top), disturbed (i.e. heavily doped) crystalline (center) and amorphous (bottom) silicon are compared:

Another difference between crystalline and amorphous materials is the occurence of optical transitions involving localized tail states in disordered systems. In the gap region of crystalline silicon below 27000 1/cm with low imaginary part of the dielectric function the same quantitiy is much larger in amorphous silicon.

Next page of this tutorial

Responsible for this page: webmaster@mtheiss.com