title: Reappraisal of variable-range hopping in quantum-dot solids.
abstract: The temperature dependence of the electrical conductivity of assemblies of ZnO nanocrystals, studied with an electrochemically gated transistor is very accurately described by the relation ln sigma=ln sigma0-(T0/T)(x) with x=2/3 over the entire temperature range from 7 to 200 K, independent of charge concentration and dielectric environment. These results cannot be explained by existing models but are supported by results on Au nanocrystals where an identical temperature dependence was observed (Zabet-Khosousi et al., Phys. Rev. Lett. 2006, 96 (15), 156403). We propose an adaptation of the Efros-Shklovskii variable-range hopping model by introducing an expression for nonresonant tunneling based on local energy fluctuations, which yields exactly the temperature dependence that is observed experimentally.
authors.affiliation: Condensed Matter and Interfaces, Debye Institute, Utrecht University, PO Box 80.000, 3508 TA Utrecht, The Netherlands. a.j.houtepen@tudelft.nl
authors.forename: Arjan J
authors.initials: AJ
authors.lastname: Houtepen
authors.forename: Daan
authors.initials: D
authors.lastname: Kockmann
authors.forename: Daniël
authors.initials: D
authors.lastname: Vanmaekelbergh
mesh_terms: D004563:Electrochemistry / Q000379:methods; D004581:Electronics; D004583:Electrons; D004867:Equipment Design; D008962:Models, Theoretical; D053758:Nanoparticles / Q000737:chemistry; D036103:Nanotechnology / Q000379:methods*; D016011:Normal Distribution; D045663:Quantum Dots; D013696:Temperature; D015034:Zinc Oxide / Q000737:chemistry
chemical_list: D015034:Zinc Oxide