Fabrication of Single-Crystal Apex for Tungsten Tip by In-Situ Thermal Treatment
Chung-Hsiang Chien1*, Hsin-Lei Chou1, Chien-Chun Chen1, Chien-Cheng Kuo1
1物理系, 國立中山大學, 高雄市, Taiwan
* presenting author:Chung-Hsiang Chien, email:chung.hsiang.chien@gmail.com
The tungsten tip has been widely used as a probe of scanning probe microscope (SPM), field ion microscopy (FIM), and a source for field emission electron. The single crystal tip in which the atomic position is well arranged is a good source of producing spin-polarized or coherent electrons, or a good template as the coordinate for the nano-objects on top. Traditionally a single crystal tip was prepared from a single crystalline tungsten rod which was grown by laser-assisted chemical vapor deposition (LCVD).[1] Here we made it by an alternative approach producing the single crystal apex through in-situ thermal treatment on a tungsten tip. In this work, the tip was prepared by electrochemically etching a tungsten wire. A sharp tip apex of 15 nm in diameter was further fabricated by focused ion beam (FIB).[2] The tip was then flashed and annealed by e-beam bombardment few seconds for several times in our home-built tip heater in which the electric field was designed to focus the e-beam on the tip apex.[3][4] The crystal plane of the prepared tip was clearly characterized in STEM measurement.[5] The results were also compared with the atomic model in different exposure planes. Our approaches demonstrated that the single crystal apex of a tungsten tip can be stably produced. The optimized conditions for making these tip will also be discussed in the presentation.

[1] Björklund, K.L et al., Materials Science & Processing,493, 4p, (2002)
[2] M. J. Vasile et al., J. Vac. Sci. Tech B 9, (1991).
[3] K. Kuroda et al., J. Electron Microsc. 179-185, 34 (1985).
[4] M. Greiner et al., Rev. Sci. Instrum. 78, 026104 (2007).
[5] E. M. James et al., J. Electron Microsc. 561-574, 47(6), (1998)

Keywords: single-crytal, tungsten tip, in-situ, thermal treatment