title: Controlling electron beam-induced structure modifications and cation exchange in cadmium sulfide-copper sulfide heterostructured nanorods.
abstract: The atomic structure and interfaces of CdS/Cu2S heterostructured nanorods are investigated with the aberration-corrected TEAM 0.5 electron microscope operated at 80 kV and 300 kV applying in-line holography and complementary techniques. Cu2S exhibits a low-chalcocite structure in pristine CdS/Cu2S nanorods. Under electron beam irradiation the Cu2S phase transforms into a high-chalcocite phase while the CdS phase maintains its wurtzite structure. Time-resolved experiments reveal that Cu(+)-Cd(2+) cation exchange at the CdS/Cu2S interfaces is stimulated by the electron beam and proceeds within an undisturbed and coherent sulfur sub-lattice. A variation of the electron beam current provides an efficient way to control and exploit such irreversible solid-state chemical processes that provide unique information about system dynamics at the atomic scale. Specifically, we show that the electron beam-induced copper-cadmium exchange is site specific and anisotropic. A resulting displacement of the CdS/Cu2S interfaces caused by beam-induced cation interdiffusion equals within a factor of 3-10 previously reported Cu diffusion length measurements in heterostructured CdS/Cu2S thin film solar cells with an activation energy of 0.96 eV.
authors.affiliation: Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
authors.forename: Haimei
authors.initials: H
authors.lastname: Zheng
authors.forename: Bryce
authors.initials: B
authors.lastname: Sadtler
authors.forename: Carsten
authors.initials: C
authors.lastname: Habenicht
authors.forename: Bert
authors.initials: B
authors.lastname: Freitag
authors.forename: A Paul
authors.initials: AP
authors.lastname: Alivisatos
authors.forename: Christian
authors.initials: C
authors.lastname: Kisielowski
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D019327:Copper Sulfate / Q000737:chemistry*; D055032:Electron Microscope Tomography / Q000379:methods*; D004583:Electrons; D043942:Nanotubes / Q000737:chemistry*; D013440:Sulfides / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D013440:Sulfides; C034939:cadmium sulfide; D019327:Copper Sulfate
keywords: Aberration corrected TEM; Electron beam irradiation; Exit-wave reconstruction; Heterostructured nanocrystals; Phase transition