Abstract
ABSTRACTScanning Tunneling Microscopy (STM) has developed into a useful tool for atomic-scale characterization of material surfaces. It is proving especially useful in the field of fracture, as the vast majority of high-resolution images of fracture processes are made in the transmission electron microscope, where thin film effects and sample preparation may greatly modify crack tip stresses and dislocation structures. This investigation involved imaging of cracks introduced in Si at room temperature and single crystals of galena (PbS) by rapid indentation at 77K. Images were obtained at the arrested cracktip, around the indentation, and along the flanks of the crack in the dynamic growth region. Measurements were made of both crack-tip morphology and upsets observed along the flanks of the cracks in PbS. Interesting results concerning crack tip geometry in Si, the effect of STM tip geometry and scan conditions on the resulting image of the cleavage crack, as well as work in progress on other material systems, will be discussed.
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