title: Metal-insulator transition in films of doped semiconductor nanocrystals.
abstract: To fully deploy the potential of semiconductor nanocrystal films as low-cost electronic materials, a better understanding of the amount of dopants required to make their conductivity metallic is needed. In bulk semiconductors, the critical concentration of electrons at the metal-insulator transition is described by the Mott criterion. Here, we theoretically derive the critical concentration nc for films of heavily doped nanocrystals devoid of ligands at their surface and in direct contact with each other. In the accompanying experiments, we investigate the conduction mechanism in films of phosphorus-doped, ligand-free silicon nanocrystals. At the largest electron concentration achieved in our samples, which is half the predicted nc, we find that the localization length of hopping electrons is close to three times the nanocrystals diameter, indicating that the film approaches the metal-insulator transition.
authors.affiliation: Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: Ting
authors.initials: T
authors.lastname: Chen
authors.affiliation: Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA.|Ioffe Institute, St Petersburg 194021, Russia.
authors.forename: K V
authors.initials: KV
authors.lastname: Reich
authors.affiliation: Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: Nicolaas J
authors.initials: NJ
authors.lastname: Kramer
authors.affiliation: Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: Han
authors.initials: H
authors.lastname: Fu
authors.affiliation: Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: Uwe R
authors.initials: UR
authors.lastname: Kortshagen
authors.affiliation: Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: B I
authors.initials: BI
authors.lastname: Shklovskii
mesh_terms: D004553:Electric Conductivity; D008567:Membranes, Artificial; D053768:Metal Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods; D010316:Particle Size; D010758:Phosphorus / Q000737:chemistry; D012666:Semiconductors; D012825:Silicon / Q000737:chemistry
chemical_list: D008567:Membranes, Artificial; D010758:Phosphorus; D012825:Silicon