title: Structural damage reduction in protected gold clusters by electron diffraction methods.
abstract: The present work explores electron diffraction methods for studying the structure of metallic clusters stabilized with thiol groups, which are susceptible to structural damage caused by electron beam irradiation. There is a compromise between the electron dose used and the size of the clusters since they have small interaction volume with electrons and as a consequence weak reflections in the diffraction patterns. The common approach of recording individual clusters using nanobeam diffraction has the problem of an increased current density. Dosage can be reduced with the use of a smaller condenser aperture and a higher condenser lens excitation, but even with those set ups collection times tend to be high. For that reason, the methods reported herein collects in a faster way diffraction patterns through the scanning across the clusters under nanobeam diffraction mode. In this way, we are able to collect a map of diffraction patterns, in areas with dispersed clusters, with short exposure times (milliseconds) using a high sensitive CMOS camera. When these maps are compared with their theoretical counterparts, oscillations of the clusters can be observed. The stability of the patterns acquired demonstrates that our methods provide a systematic and precise way to unveil the structure of atomic clusters without extensive detrimental damage of their crystallinity.
authors.affiliation: Department of Physics and Astronomy, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 USA.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Ortega
authors.affiliation: Department of Physics and Astronomy, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 USA.
authors.forename: Arturo
authors.initials: A
authors.lastname: Ponce
authors.affiliation: Department of Physics and Astronomy, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 USA.
authors.forename: Ulises
authors.initials: U
authors.lastname: Santiago
authors.affiliation: Department of Physics and Astronomy, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 USA.
authors.forename: Diego
authors.initials: D
authors.lastname: Alducin
authors.affiliation: Department of Physics and Astronomy, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 USA.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Benitez-Lara
authors.affiliation: Department of Physics and Astronomy, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 USA.
authors.forename: Germán
authors.initials: G
authors.lastname: Plascencia-Villa
authors.affiliation: Department of Physics and Astronomy, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 USA.
authors.forename: Miguel
authors.initials: M
authors.lastname: José-Yacamán
keywords: Damage reduction; Nanobeam electron diffraction; Scanning transmission electron microscopy; Thiolate-protected gold clusters