| Summary: | 碩士 === 國立嘉義大學 === 光電暨固態電子研究所 === 98 === In this thesis, we developed an improved electrochemical etching method combined with the automatic power cut-off system for the reproducible fabrication of sharp ferromagnetic tips used in spin polarized scanning tunneling microscopy (SP-STM). By using the automatic power cut-off circuit system, it can cut off power in time to avoid over-etching the apex of the tip. After testing different DC voltages for the circuit of electrochemical etching system, a sharp Ni tip with a lowest aspect ratio can be obtained at 8V DC voltage. We also studied different kinds of electrolytes and various concentrations of electrolytes for electrochemical etching of nickel probe, it was found that etching results of HCl solution are better than those of the KCl solution. Moreover, the best etching result of nickel tip was obtained by using the concentration of HCl at 1.5 M.
In addition, a plastic cube of 1.33 g is attached to the end of an immersed nickel wire, this leads to a sharp nickel tip with an apex size about 100nm and the reproducible rate better than 40%. Finally, the tip apex was etched in HF (40~48%) for 20 seconds, this not only removes the oxide but also improves the tip shape and reduces the curvature radius of Ni tip.
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