Hello Anjani. Think about it in the following way. When it is micro range the energy levels of individual atoms form bands as you know. As you decrease the size then there are less atoms and orbitals that compose the bands resemble energy levels rather than bands. Thus you can expect different properties in the nanorange compared to micro range.
Hello Anjani. Think about it in the following way. When it is micro range the energy levels of individual atoms form bands as you know. As you decrease the size then there are less atoms and orbitals that compose the bands resemble energy levels rather than bands. Thus you can expect different properties in the nanorange compared to micro range.
Hi,
the change of the band gap of a material reduced to nanometer size is intrinsically connected with the quantum mechanics of the base; the reduction of scale along one or more dimensions of the material implies a quantum confinement of electrons in the valence bands that are affected by a potential barrier infinite in the direction of confinement, that hole has been linked with n eigenfunctions with alternating parity: the ground state has eigenfunction always equal and the respective autoenergies are given by:
E= (n*/hbar*/pi^2)/(2*m*L^2)
where you can see a dependence of the energy is inversely proportional to the mass and the square of the size of the hole (coincident with the size of your system reduced).
More little is the system, larger is the spread in energy and respective eigenenergie of the state.
Another way to understand it is simply related to the Heisenberg uncertainty principle, between momentum and position. A reduction of the size of the system provides a minor indetermination over position, then you have to expect a larger uncertainty in energy. The fact that you can see this only if you are in nanoscale size is related to the Planck's constant...larger size than nanoscale, cannot shows quantum effects.
This tunability of the band gap of the nanostructures is, for example, employed in semiconductor physics to create materials which, with specific dimensions, can absdorb or emit at different frequency.
I hope it is the answer that you search.
Cheers,
A.
Try to understand how band-gap is formed in a crystalline solid...just do careful analysis..
When more and more atoms come close to each other, their energy levels interact. Due to which energy of some levels increase and of some levels decreases, consequently they form bands. Now think opposite, when we think about nano sized range, there are less number of atoms, whose energy levels are interacting, then obviously less change in energies of various level and consequently different band gap compared to bulk material...
Splitting of energy levels in to bands is because of coupled interaction between atoms and the equilibrium separation between atoms. When we decrease the particle size and enter into nano, the atomic concentration and the separation between atoms may effect, as a result energy gap will changed.
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