Variable range hopping conduction in semiconductor nanocrystal solids

The temperature and electrical field dependent conductivity of n-type CdSe nanocrystal thin films is investigated. In the low electrical field regime, the conductivity follows sigmasimilar toexp[-(T*/T)(1/2)] in the temperature range 10<120 K. At high electrical field, the conductivity is strongly field dependent. At 4 K, the conductance increases by 8 orders of magnitude over one decade of bias. At a very high field, conductivity is temperature independent with sigmasimilar toexp[-(E*/E)(1/2)]. The complete behavior is very well described by variable range hopping with a Coulomb gap.