Density of states X

Figure X. Density of states for metal (a) and semiconductor (b) nanocrystals. In each case, the density of states is discrete at the band edges. The Fermi level is in the center of a band in a metal, and so kT may exceed the electronic energy level spacing even at room temperatures and small sizes. In contrast, in semiconductors, the Fermi level lies between two bands, so that the relevant level spacing remains large even at small sizes. The HOMO-LUMO gap increases in semiconductor nanocrystals of smaller sizes.

Substance Minimum Energy Gap, eV R.T. OK dEg dT xlO eV/°C dEg dP xlO eV cm /kg Density of States Electron Effective Mass (mo) Electron Mobility and Temperature Dependence cm /Vs —X Density of States Hole Effective Mass mdp, (mo) Hole Mobilit)r and Temperature Dependence cm lV s —X ... 

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