| Summary: | 碩士 === 國立臺灣大學 === 物理研究所 === 93 === We fabricate a stable dual ion/electron point source based on In-Bi alloy. As a liquid metal ion source (LMIS), its emission performance at about 70 – 100℃ is comparable to that of commercial Ga-LMIS. After the In-Bi source is solidified, field electron microscopy is employed to study the pattern of electron emission. In-Bi alloy is inherently soft so that its electron emission is easy to be unstable. To remedy this disadvantage, the In-Bi alloy is loaded onto a sharp tungsten tip fabricated by electrochemical etching. The resulting source exhibits electron emission characteristics comparable to that of Au-In alloy.
We also investigate the correlation between surface morphology of an In/W emitter and its electron emission behavior and observe that, after long-term electron emission, some underlying W migrates to the surface. We attribute the tungsten migration to high electron emission current density. Interestingly, the migration leads to a protrusion with specific geometry on the apex of tip and such an In/W emitter constitutes a dual ion/electron emitter with good electron emission properties. Furthermore, stable ion and electron emission can be interchangeably extracted from the source. Both the successful fabrication of the In-Bi/W and In/W stable dual ion/electron point sources are important steps towards the further development of single-column focused ion/electron beam systems.
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