Register to reply

Transmittance, Reflectivity and Band gap

Share this thread:
Jun8-10, 06:49 PM
P: 42
I was wondering that how the knowledge o transmittance and reflectance curves can give us information about the band gap and electronic structure of a metal? How these curve differ for semiconductors? I desperately tried to extract n, k values from the reflectance curve of a nitride material about which I have no information whether it is metallic or semiconducting. Is there any way to do that?
Phys.Org News Partner Physics news on
New complex oxides could advance memory devices
'Squid skin' metamaterials project yields vivid color display
Scientists control surface tension to manipulate liquid metals (w/ Video)
Jun9-10, 06:15 PM
P: 42
No one seems to be interested so I present my own explanation to see if some one agrees or not. consider the case of semiconductor transmission, since there is a band gap (see schematic fig, energy values increase towards right and transmission upwards) so material is fairly opaque in highe energy range but there is abrupt change at the onset of absorption and in IR range it becomes transmitting. Transmission stays flat there because there are only interband transitions. On the other hand for metal, we almost similar behavior by the metal in the high energy range and at the band gap (band gap does not necessarily mean a material is semiconducting until and unless we have several other calculations to support SC state) but in low frequency region we again fall in the transmission. Possible explanation for this fall might that electrons very close to surface absorb EM waves, vibrate and loose energy. This energy can be seen as reflection (which will be less than transmission but still can be significant). Finally not to mention that there is a reasonably good amount of absorption as well. What does this explanation sound like?
Secondly let us say we have reflectance curve instead of transmission then how can I calculate n, k vaules from it? I know the reflectivity formula and I am afraid to use (alpha= 4pi*k/lambda) to find k values. It gives wron answer.
Attached Thumbnails
metal.jpg   sc.jpg  
Jun10-10, 02:12 AM
Sci Advisor
P: 3,633
Almost every book on solid state physics should have a chapter on optical properties.
I recommend Ashcroft Mermin, solid state physics. An interesting source is also Landolt Boernstein.

Dr Transport
Jun11-10, 07:44 PM
Sci Advisor
PF Gold
P: 1,481
Transmittance, Reflectivity and Band gap

Yu and Cardona's text is much better than Ashcroft and Mermin for optical properties materials.

The Landolt-Borstein books are reference tables of properties and not a text per say.

Register to reply

Related Discussions
Light Transmittance Introductory Physics Homework 3
Material for a high transmittance Prism and where to Buy General Physics 5
Color transmittance measurement General Physics 1
Energy given off Photons/Heat from Conduction Band (Conduct Electron) to Valance band Atomic, Solid State, Comp. Physics 3
Valance band to Conduction Band (Valance Electron), Energy Band Gap Levels Advanced Physics Homework 0