what is interband transition ?

Question

I'm studying transparent conducting oxide now. One of the requirement of TCO materials is >> there can be no interband transition less than 3.1 eV in energy. This limits consideration to cations with filled d-shells, such as 3d10Cu+, Zn2+, Ga3+, 4d10 Ag+, Cd2+, In3+ and Sn4+.

Could somebody explain to me what does it mean ? Thanx

Answer 1

Basically what this is referring to is the ionization of the atoms you have listed. this occurs when there is a shift in the distribution of the electron in the various bands 'orbiting' the nucleus of the atom, or a proton has been added to the nucleus.

What the statement seems to be refering to is the creation of a positive ion (cation). If this is to occur it needs a shift in the distribution of the electrons in the shells. To move an electron from one band to another, or to excite one enough to be lost fully from orbit you will need a level of energy.

In the cases stated, I would say that 3.1eV is the minimum energy required to create a transition of an electron between the bands or to lose an electron and so create the ion.

Hope that helps.

Answer 2

The tight-binding energy band structures of BaTiO3 and KNbO3 have been determined in the cubic and tetragonal phases. The modifications at the para-ferroelectric change are analysed through the orbital interactions. The evaluation of the interband transition moment at different points of the Brillouin zone reveals the main interband transition, giving rise to the first optical structure. The Delta -band pairs which run nearly parallel determine the optical and dielectric properties. An optical matrix element investigation provides the parameters which determine the anisotropy. The evolution of the refractive index during the phase change is described through the decrease of interband transition strengths along the polar axis and the upward shift of the transition energies. The polarisation-induced band edge effects are estimated and connected with Bloch orbital interactions. Experimental results on the band gap and refractive index near the transition for T>Tc associated with precursor polarisation can be interpreted from this model. The long- and short-range interactions, expressed through the Bloch orbital interactions. allow the para-ferroelectric phase change to be described.

Answer 3

Wow, if you got that second one I'll buy the next round!!

Visible light wavelength ranges from 380 to 780 nm (in the broadest interpretations). 3.1 eV is exactly 400 nm, the cut on for visible light. Photons of higher energy absorbed by interband transitions will not effect the T in TCO.

Ag is by far the most common TCO