Variable range hopping conduction in semiconductor nanocrystal solids

TL;DR

This study investigates the variable range hopping conduction mechanism in n-type CdSe nanocrystal films, revealing temperature and electric field dependencies consistent with Coulomb gap models, with significant conductance changes at low temperatures and high fields.

Contribution

It demonstrates that the conductivity in CdSe nanocrystal solids follows a Coulomb gap variable range hopping model across various temperatures and electric fields, providing detailed experimental validation.

Findings

Conductivity follows G ~ exp(-(T*/T)^0.5) at low fields and 10K<T<120K.

At high fields, conductance increases dramatically, with G ~ exp(-(E*/E)^0.5).

Conductivity becomes temperature-independent at very high fields and low temperatures.

Abstract

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 G ~ exp(-(T*/T)^0.5) in the temperature range 10K<T<120K. At high electrical field, the conductivity is strongly field dependent. At 4K, the conductance increases by eight orders of magnitude over one decade of bias. At very high field, conductivity is temperature-independent with G ~ exp(-(E*/E)^0.5). The complete behavior is very well described by variable range hopping with Coulomb gap.