title: Processing-Structure-Property Relationships in Laser-Annealed PbSe Nanocrystal Thin Films.
abstract: As nanocrystal (NC) synthesis techniques and device architectures advance, it becomes increasingly apparent that new ways of connecting NCs with each other and their external environment are required to realize their considerable potential. Enhancing inter-NC coupling by thermal annealing has been a long-standing challenge. Conventional thermal annealing approaches are limited by the challenge of annealing the NC at sufficiently high temperatures to remove surface-bound ligands while at the same time limiting the thermal budget to prevent large-scale aggregation. Here we investigate nonequilibrium laser annealing of NC thin films that enables separation of the kinetic and thermodynamic aspects of nanocrystal fusion. We show that laser annealing of NC assemblies on nano- to microsecond time scales can transform initially isolated NCs in a thin film into an interconnected structure in which proximate dots "just touch". We investigate both pulsed laser annealing and laser spike annealing and show that both annealing methods can produce "confined-but-connected" nanocrystal films. We develop a thermal transport model to rationalize the differences in resulting film morphologies. Finally we show that the insights gained from study of nanocrystal mono- and bilayers can be extended to three-dimensional NC films. The basic processing-structure-property relationships established in this work provide guidance to future advances in creating functional thin films in which constituent NCs can purposefully interact.
authors: †Department of Materials Science and Engineering, ‡Cornell High Energy Synchrotron Source, and §School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14850, United States.
authors: Benjamin E
authors: BE
authors: Treml
authors: †Department of Materials Science and Engineering, ‡Cornell High Energy Synchrotron Source, and §School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14850, United States.
authors: Andrew B
authors: AB
authors: Robbins
authors: †Department of Materials Science and Engineering, ‡Cornell High Energy Synchrotron Source, and §School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14850, United States.
authors: Kevin
authors: K
authors: Whitham
authors: †Department of Materials Science and Engineering, ‡Cornell High Energy Synchrotron Source, and §School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14850, United States.
authors: Detlef-M
authors: DM
authors: Smilgies
authors: †Department of Materials Science and Engineering, ‡Cornell High Energy Synchrotron Source, and §School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14850, United States.
authors: Michael O
authors: MO
authors: Thompson
authors: †Department of Materials Science and Engineering, ‡Cornell High Energy Synchrotron Source, and §School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14850, United States.
authors: Tobias
authors: T
authors: Hanrath
mesh_terms: D006358:Hot Temperature; D007834:Lasers; D007854:Lead / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D053758:Nanoparticles / Q000737:chemistry*; D018036:Selenium Compounds / Q000737:chemistry*
chemical_list: D018036:Selenium Compounds; C088065:lead selenide; D007854:Lead
keywords: diffusion; laser annealing; nanocrystal; quantum confinement; thin films