Berlin 2005 – wissenschaftliches Programm
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O: Oberflächenphysik
O 34: Rastersondentechniken II
O 34.4: Vortrag
Montag, 7. März 2005, 11:30–11:45, TU EB407
Nanoindentation with Atomically Defined Tips — •Andre Schirmeisen1 und Graham Cross2 — 1Center for Nanotechnology (CeNTech), University of Münster, Wilhelm-Klemm-Str.10, 48149 Münster — 2SFI Trinity Nanoscience Bldg, Trinity College, Dublin 2, Ireland
An atomically defined tungsten asperity of 3 nm radius was fabricated and imaged by field ion microscopy and brought into contact with a Au(111) terrace in ultra-high vacuum conditions. The mechanical evolution of the asperity contact under cyclic indentation testing was monitored by a simultaneous load-displacement and electrical current-displacement measurement. Adhesive forces of 10 nN consistent with short range chemical bonding were measured. Compressive loads of up to 100 nN under displacements of 1.5 nm, equivalent to 5 atomic gold layers, were recorded. Load displacement curves of the pristine surface showed multiple pop-in events during loading, which indicate the creation of nanoscale dislocations in the sample material. More interestingly, during unloading, we found correlated pop-out events, which indicate the occurrence of complete self-healing of the induced dislocation. The energy dissipated during those reversable dislocation creation and healing events can be directly measured in our experiments. These values are in good agreement with recent molecular dynamics simulations of incipient plasticity in asperity contacts.