Investigation of field electron microscope tips bombarded with microparticles at limited field emission currents |
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Authors: | R Vanselow R D Helwig |
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Institution: | (1) Department of Chemistry and Laboratory for Surface Studies, University of Wisconsin-Milwaukee, 53201 Milwaukee, Wisconsin, USA |
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Abstract: | Mo, Ta, W, and Re field electron microscope (FEM) tips, bombarded with microparticles at limited field emission currents (400
MΩ resistor in series with the FEM tip) were investigated by means of FEM, transmission electron microscopy (TEM), and scanning
electron microscopy (SEM). Two groups of tips could be distinguished: One group had a slight tip radius increase to a maximum
of 2.5 μm and microcraters were formed along the tip shank. The other group had no detectable tip radius change; however,
there was microcrater formation near the tip apex area. FEM patterns showed surface contamination clearly. Heating such contaminated
tips and tips where phosphorescent material (Zn:Cd)S had been deposited in less than monolayer concentration by evaporation
from a heating coil, resulted in similar sequences of FEM patterns. A new type of microcrater with smooth crater lips could
be detected in both groups. These results support the combined microparticle-field emission mechanism 1], which was proposed
earlier to be responsible for melting cap and microcrater formation.
Excerpts were presented at the 19th Field Emission Symposium, Urbana, Illinois (USA), August 1972. |
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Keywords: | Field electron microscopy Microcrater formation |
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