| AVS 65th International Symposium & Exhibition | |
| Advanced Ion Microscopy Focus Topic | Thursday Sessions |
| Session HI-ThA |
| Session: | Emerging Ion Sources, Optics, and Applications |
| Presenter: | Kwang-Il Kim, University of Science and Technology, Republic of Korea |
| Authors: | K.I. Kim, University of Science and Technology, Republic of Korea Y.H. Kim, Korea Research Institute of Standards and Science (KRISS), Republic of Korea T. Ogawa, Korea Research Institute of Standards and Science (KRISS), Republic of Korea S.J. Choi, Kyungpook National University, Republic of Korea B. Cho, Korea Research Institute of Standards and Science (KRISS), Republic of Korea S.J. Ahn, Korea Research Institute of Standards and Science (KRISS), Republic of Korea I.-Y. Park, Korea Research Institute of Standards and Science (KRISS), Republic of Korea |
| Correspondent: | Click to Email |
The application of the helium ion microscope (HIM) has expanded in various fields, such as nano-patterning, material science, and biology, due to its high spatial resolution for imaging and high-precision machining [1-3]. HIM realized sub-nm resolution with gas field ion sources (GFIS) which generate s ion beams from one or three topmost atoms of tips to obtain high beam current density. However, it is difficult to fabricate atomically sharp tips, such as trimer/single atom tip (TSAT), in an ultra-high vacuum (UHV) condition. TSAT can be typically fabricated by either a build-up method or field-assisted reactive gas etching method with oxygen and nitrogen [4-7]. However, these methods usually adopt resistive tip heating at about 1000 K as pre-cleaning of tip surface before the tip sharpening process. This heating leads to complex system because of a power supply circuit to provide or flow a current through a heating loop, where the tip was welded. In our study, we show that TSAT can be fabricated by field evaporation effect with an oxide layer which remains on the tip surface owing to the absence of tip heating.
As the result of this study, we could get a single crystalline field ion microscopy (FIM) image of W(111) with fabricating a TSAT by field evaporation phenomenon without tip surface cleaning by high temperature heating process. The oxide layer which remained after electrochemical etching process induces etch-like phenomenon in UHV condition without any additional gas injection. In order to analyze verify the proposed etching process, the analytical techniques of transmission electron microscope (TEM), energy filtered transmission electron microscope (EFTEM), and electron energy loss spectroscopy (EELS) were used. To compare the etching results whether the insulating layer present or not, we did additional experiment for tip heating. It was found that tungsten oxides contained in the insulating layer of the tip surface causes the etching. This method is much simpler than conventional methods because it uses only field evaporation phenomenon for fabricating TSAT. Therefore, we can simplify the equipment configuration since there is no need to heat the tip.
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[2] M.Postek et al., Scanning Microscopy 2009 (Vol. 7378, p. 737808)
[3] Joy, D. C. (2013). Helium Ion Microscopy: Principles and Applications (pp. 1-64). New York: Springer.
[4] M. Rezeq et al., The Journal of chemical physics, 124(20), 204716, 2006
[5] F.Rahman et al., Surface Science, 602(12), 2128-2134, 2008
[6] VT Binh et al., Surface Science, 202(1-2), L539-L549, 1988
[7] TY Fu et al., Physical Review B, 64(11), 113401, 2001