title: High resolution electron microscopy of Ag-clusters in crystalline and non-crystalline morphologies grown inside superfluid helium nanodroplets.
abstract: We present a first investigation of structural properties of Ag clusters with a diameter of up to 5.5 nm grown inside superfluid helium nanodroplets (He(N)) and deposited on an amorphous C surface. With high resolution transmission electron microscope images we are able to show that in addition to the crystalline face centered cubic (fcc) structure, noncrystalline icosahedral (Ih), and decahedral (Dh) morphologies are grown. Relative abundances (56% fcc, 31% Dh, and 13% Ih) as well as the size distribution of each morphology (mean diameters d(fcc)=2.62(5) nm, d(Dh)=3.34(7) nm, and d(Ih)=3.93(2) nm) do not reflect the situation expected from pure energetic considerations, where small Ihs should be followed by medium sized Dhs and large fccs. Instead, kinetic factors seem to play an important role in the formation of these structures, as it appears to be the case for clusters formed by inert gas aggregation. Considering the low temperatures (0.37 K) and extremely high cooling rates, we discuss basic ideas that might lead to a qualitative picture of the cluster formation process inside He(N).
authors.affiliation: Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
authors.forename: Alexander
authors.initials: A
authors.lastname: Volk
authors.forename: Philipp
authors.initials: P
authors.lastname: Thaler
authors.forename: Markus
authors.initials: M
authors.lastname: Koch
authors.forename: Evelin
authors.initials: E
authors.lastname: Fisslthaler
authors.forename: Werner
authors.initials: W
authors.lastname: Grogger
authors.forename: Wolfgang E
authors.initials: WE
authors.lastname: Ernst