Studies on Explosive Emission & Material Degradation of Nanoscale Metal Emitter Tips based on Molecular Dynamics Analysis

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2017-10-30

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Abstract

Molecular dynamics (MD) simulations were carried out to study the potential for material degradation from a copper nanoprotrusion under high electric field conditions. The distribution of Maxwell tensile stress and Joule heating induced by electric field of a three-dimensional system were calculated based on COMSOL software. Those results were used in LAMMPS to simulate the operations of nanoprotrusion in various settings. The simulations consist of two different methods. The first method employed constant temperature for each run. Several simulations for same model were performed by running at different temperatures to probe the effect of Joule heating of the nanoprotrusion. A second method was then also advanced which allowed for heating within each MD simulation. The system was then subjected to increasing temperatures when an external electric field was applied. The results in this thesis show that mass ejection from a nanoprotrusion will take place when the electric field surrounding the nanoprotrusion is strong enough. The model with higher field was also influenced by a stronger Maxwell stress and higher temperatures. Both of these factors drive the structural instability. In the case with a 3 V/nm field applied, the mass ejection through the tip was predicted when the nanoprotrusion was heated up by the high current density. Besides, it was shown that the electric field gets enhanced when the shape of nanoprotrusion has a higher aspect ratios. In this scenario, the requirement of field and temperature for mass ejection is predicted to reduce.

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Nanoprotrusions, Molecular dynamics

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