Lattice Damage by Mechanical and Electrical Contacts Investigated by Field Ion Microscopy.
PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB
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Using the atomic resolution of the field ion microscope, mechanical contacts between tungsten and platinum were performed at cryogenic temperatures under ultra-high-vacuum conditions. The absence of plastic deformation in tungsten tips the damage was confined to the top 3 to 5 atomic layers indicated purely elastic deformation provided the tip was not buckled by a lateral load component. This shallow damage depth was similarly observed in platinum tips, but in contrast to tungsten, plastic deformation by twinning and slip on the 111 planes was also found. The experimental results were compared to the predictions of the Hertz theory of elastic deformation, with deviations explainable in terms of the vibration limit of the apparatus, of adhesion forces between the metal surfaces, and of work hardening of the platinum plate. Electrical contacts between tungsten tips and the platinum plate show a strong voltage dependence, while the effect of the current is unexpectedly small. A model consistent with these results is based on resistive heating by a field emission current in the narrow gap. Author
- Electrical and Electronic Equipment