Hostname: page-component-848d4c4894-x5gtn Total loading time: 0 Render date: 2024-05-21T23:18:38.250Z Has data issue: false hasContentIssue false

Evaluating Angular Ion Current Density for Atomically Defined Nanotips

Published online by Cambridge University Press:  10 July 2014

Radovan Urban*
Department of Physics, University of Alberta, Edmonton, AB, Canada T6G 2G9 National Institute for Nanotechnology, Edmonton, AB, Canada T6G 2M9
Robert A. Wolkow
Department of Physics, University of Alberta, Edmonton, AB, Canada T6G 2G9 National Institute for Nanotechnology, Edmonton, AB, Canada T6G 2M9
Jason L. Pitters
National Institute for Nanotechnology, Edmonton, AB, Canada T6G 2M9
*Corresponding author.
Get access


In this paper we investigate methods to characterize angular current density from atomically defined gas field ion sources. We show that the ion beam emitted from a single apex atom is described by a two-dimensional Gaussian profile. Owing to the Gaussian shape of the beam and the requirement to collect the majority of the ion current, fixed apertures have inhomogeneous illumination. Therefore, angular current density measurements through a fixed aperture record averaged angular current density. This makes comparison of data difficult as averaged angular current density depends on aperture size. For the same reasons, voltage normalization cannot be performed for fixed aperture measurements except for aperture sizes that are infinitely small. Consistent determination of angular current density and voltage normalization, however, can be achieved if the beam diameter as well as total ion current are known. In cases where beam profile cannot be directly imaged with a field ion microscope, the beam profile could be extracted from measurements taken at multiple acceleration voltages and/or with multiple aperture sizes.

Materials Applications
© Microscopy Society of America 2014 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)


Borret, R., Bohringer, K. & Kalbitzer, S. (1990). Current-voltage characteristics of a gas field ion source with a supertip. J Phys D 23, 1271.CrossRefGoogle Scholar
Bronsgeest, M., Barth, J., Swanson, L. & Kruit, P. (2008). Probe current, probe size, and the practical brightness for probe forming systems. J Vac Sci Techol B 26(3), 949955.CrossRefGoogle Scholar
Edinger, K., Yun, V., Melngailis, J., Orloff, J. & Magera, G. (1997). Development of a high brightness gas field ion source. J Vac Sci Technol B 15, 2365.CrossRefGoogle Scholar
Fink, H. (1986). Mono-atomic tips for scanning tunneling microscopy. IBM J Res Dev 30(5), 460465.CrossRefGoogle Scholar
Hanson, G.R. & Siegel, B.M. (1979). H2 and rare gas field ion source with high angular current. J Vac Sci Technol 16, 1875.CrossRefGoogle Scholar
Hawkes, P. & Kasper, E. (1989). Principles of Electron Optics, vol. 2, chapter 47, London, San Diego: Academic Press.Google Scholar
Hiroshima, H., Komuro, M., Konishi, M. & Tsumori, T. (1992). A focused He+ ion beam with a high angular current density. Jpn J Appl Phys 31(Part 1, No. 12B), 44924495. Available at Scholar
Jousten, K., Bohringer, K., Borret, R. & Kalbitzer, S. (1988). Growth and current characteristics of stable protrusions on tungsten field ion emitters. Ultramicroscopy 26(3), 301312.CrossRefGoogle Scholar
Kobayashi, Y., Sugiyama, Y., Morikawa, Y., Kajiwara, K. & Hata, K. (2010). Experimental evaluation of the influence of shank shape of field ion emitter on the angular current density. J Vac Sci Technol B 28, C2A90C2A93.CrossRefGoogle Scholar
Kuo, H.-S., Hwang, I.-S., Fu, T.-Y., Hwang, Y.-S., Lu, Y.-H., Lin, C.-Y., Hou, J.-L. & Tsong, T.T. (2009). A single-atom sharp iridium tip as an emitter of gas field ion sources. Nanotechnology 20, 335701.CrossRefGoogle ScholarPubMed
Kuo, H.-S., Hwang, I.-S., Fu, T.-Y., Lu, Y.-H., Lin, C.-Y. & Tsong, T.T. (2008). Gas field ion source from an Ir/W<111> single-atom tips. Appl Phys Lett 92, 063106.CrossRefGoogle Scholar
Kuo, H.-S., Hwang, I.-S., Fu, T.-Y., Wu, J.-Y., Chang, C.-C. & Tsong, T.T. (2004). Preparation and characterization of single-atom tips. Nano Lett 4, 23792382.CrossRefGoogle Scholar
Langmuir, D. (1937). Theoretical limitations of cathode-ray tubes. Proc Inst Radio Eng 25(8), 977991.Google Scholar
Onoda, J. & Mizuno, S. (2011). Fabrication of <110> oriented tungsten nano-tips by field-assisted water etching. Appl Surf Sci 257(20), 84278432.CrossRefGoogle Scholar
Purcell, S., Binh, V. & Thevenard, P. (2001). Atomic-size metal ion sources: Principles and use. Nanotechnology 12, 168172.CrossRefGoogle Scholar
Rezeq, M., Pitters, J. & Wolkow, R. (2006). Tungsten nano-tip fabrication by spatially controlled field-assisted reaction with nitrogen. J Chem Phys 124, 204716.CrossRefGoogle Scholar
Sakata, T., Kumagai, K., Naitou, M., Watanabe, I., Ohhashi, Y., Hosoda, O., Kokubo, Y. & Tanaka, K. (1992). Helium field ion source for application in a 100 keV focused ion beam system. J Vac Sci Technol B 10, 28422845.CrossRefGoogle Scholar
Schwoebel, P.R. & Hanson, G.R. (1985). Beam current stability from localized emission sites in a field ion source. J Vac Sci Technol B 3, 214.CrossRefGoogle Scholar
Spence, J.C.H., Qian, W. & Silverman, M.P. (1994). Electron source brightness and degeneracy from Fresnel fringes in field emission point projection microscopy. J Vac Sci Techol A 12, 542547.CrossRefGoogle Scholar
Tondare, V. (2005). Quest for high brightness, monochromatic noble gas ion sources. J Vac Sci Technol A 23, 1498.CrossRefGoogle Scholar
Urban, R., Pitters, J.L. & Wolkow, R.A. (2012 a). Field ion microscope evaluation of tungsten nanotip shape using He and Ne imaging gases. Ultramicroscopy 122, 6064.CrossRefGoogle Scholar
Urban, R., Pitters, J.L. & Wolkow, R.A. (2012 b). Gas field ion source current stability for trimer and single atom terminated W(111) tips. Appl Phys Lett 100, 263105.CrossRefGoogle Scholar
Völkl, E., Allard, L. & Joy, D. (Eds.) (1999). Introduction to Electron Holography. New York: Plenum Publishers.CrossRefGoogle Scholar
Ward, B., Notte, J. & Economou, N. (2006). Helium ion microscope: A new tool for nanoscale microscopy and metrology. J Vac Sci Technol B 24, 2871.CrossRefGoogle Scholar
Wiesner, J.C. & Everhart, T.E. (1973). Point-cathode electron sources-electron optics of the initial diode region. J Appl Phys 44, 21402148.CrossRefGoogle Scholar
Witt, J. & Müller, K. (1986). Computer-aided measurements of FIM intensities. J Physique 47, c2-465c2-470.Google Scholar