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Investigation of atomic structure ahead of crack tip by STM and AFM

The nanostructure and atomic structure ahead of the crack tip of highly oriented pyrolytic graphite has been studied by using scanning tunneling microscopy (STM) and that of mica by using atomic force microscopy (AFM). There are many small voids or vacancy clusters ahead of the crack tip, which can migrate with time and result in the crack tip propagating because of the interaction force between the STM pinpoint and the sample. The nanostructure and atomic structure of loaded crack tip on (001) surface of mica has been observed by AFM. The results show that there exists a severely distorted region about 10 nm in width ahead of the loaded crack tip, and in this region there are many vacancies and vacancy clusters. Around this region there is an abnormal elastic region about 110 nm in width.