Regensburg 2025 – scientific programme
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O: Fachverband Oberflächenphysik
O 6: Oxides and Insulator Surfaces: Structure, Epitaxy and Growth
O 6.9: Talk
Monday, March 17, 2025, 12:30–12:45, H8
Surface Reconstructions Govern Ice Nucleation on Silver Iodide – A Noncontact-AFM Investigation — •Johanna I. Hütner1, Andrea Conti1, David Kugler1, Franziska Sabath3, Florian Mittendorfer1, Michael Schmid1, Angelika Kühnle2, Ulrike Diebold1, and Jan Balajka1 — 1Institute of Applied Physics, TU Wien, Vienna, 1040, Austria — 2Department of Chemistry, Bielefeld University, Bielefeld, 33615, Germany — 3Max Planck Institute for Polymer Research, Mainz, 55128, Germany
Silver iodide (AgI) is used as a cloud seeding material due to its ability to nucleate ice efficiently, which is explained by the good lattice match between AgI and hexagonal ice. However, AgI consists of stacked planes of positively charged Ag+ alternating with negatively charged I–. Cleaving a AgI crystal along the (0001) plane thus exposes Ag+ and I– terminated surfaces. Both terminations are polar and inherently unstable.
We present atomically resolved noncontact atomic force microscopy (NC-AFM) images that show how AgI(0001) surfaces compensate for this non-zero electric dipole perpendicular to the surface. Both Ag and I terminated surfaces form reconstructions, whose structure affects their ice nucleating abilities. NC-AFM images of UHV-cleaved surfaces exposed to water vapor reveal that ice forms an epitaxial layer only on the Ag terminated surface, whereas on the I termination ice forms three-dimensional clusters.
These atomic-level observations could enhance our understanding of ice formation processes in the atmosphere.
Keywords: AFM; polar surface; ice