Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

High-endurance micro-engineered LaB6 nanowire electron source for high-resolution electron microscopy


The size tunability and chemical versatility of nanostructures enable electron sources of high brightness and temporal coherence, both of which are important characteristics for high-resolution electron microscopy1,2,3. Despite intensive research efforts in the field, so far, only conventional field emitters based on a bulk tungsten (W) needle have been able to yield atomic-resolution images. The absence of viable alternatives is in part caused by insufficient fabrication precision for nanostructured sources, which require an alignment precision of subdegree angular deviation of a nanometre-sized emission area with the macroscopic emitter axis4. To overcome this challenge, in this work we micro-engineered a LaB6 nanowire-based electron source that emitted a highly collimated electron beam with good lateral and angular alignment. We integrated a passive collimator structure into the support needle tip for the LaB6 nanowire emitter. The collimator formed an axially symmetric electric field around the emission tip of the nanowire. Furthermore, by means of micromanipulation, the support needle tip was bent to align the emitted electron beam with the emitter axis. After installation in an aberration-corrected transmission electron microscope, we characterized the performance of the electron source in a vacuum of 10−8 Pa and achieved atomic resolution in both broad-beam and probe-forming modes at 60 kV beam energy. The natural, unmonochromated 0.20 eV electron energy loss spectroscopy resolution, 20% probe-forming efficiency and 0.4% probe current peak-to-peak noise ratio paired with modest vacuum requirements make the LaB6 nanowire-based electron source an attractive alternative to the standard W-based sources for low-cost electron beam instruments.

This is a preview of subscription content, access via your institution

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Micro-engineering of a NW electron source.
Fig. 2: Coherent TEM imaging using a LaB6 NW electron gun.
Fig. 3: Aberration-corrected STEM imaging using a LaB6 NW electron gun.
Fig. 4: Unmonochromated EELS energy resolution.

Data availability

Additional data and raw data are available from the corresponding author upon reasonable request.

Code availability

The code that has been used for this work is available from the corresponding author upon reasonable request.


  1. Zhang, H. et al. An ultrabright and monochromatic electron point source made of a LaB6 nanowire. Nat. Nanotechnol. 11, 273–279 (2016).

    Article  CAS  Google Scholar 

  2. De Jonge, N., Lamy, Y., Schoots, K. & Oosterkamp, T. High brightness electron beam from a multi-walled carbon nanotube. Nature 420, 393–395 (2002).

    Article  Google Scholar 

  3. Williams, D. & Carter, C. Transmission Electron Microscopy: A Textbook for Materials Science Vol. 1 (Springer, 2009).

  4. Swanson, L. & Schwind, G. A review of the cold-field electron cathode. Adv. Imaging Electron Phys. 159, 63–100 (2009).

    Article  CAS  Google Scholar 

  5. Cho, B., Ichimura, T., Shimizu, R. & Oshima, C. Quantitative evaluation of spatial coherence of the electron beam from low temperature field emitters. Phys. Rev. Lett. 92, 246103 (2004).

    Article  CAS  Google Scholar 

  6. Fink, H., Stocker, W. & Schmid, H. Holography with low-energy electrons. Phys. Rev. Lett. 65, 1204–1206 (1990).

    Article  CAS  Google Scholar 

  7. Gadzuk, J. & Plummer, E. Field emission energy distribution (FEED). Rev. Mod. Phys. 45, 487–548 (1973).

    Article  CAS  Google Scholar 

  8. Krivanek, O. et al. Atom-by-atom structural and chemical analysis by annular dark-field electron microscopy. Nature 464, 571–574 (2010).

    Article  CAS  Google Scholar 

  9. Haruta, M. & Kurata, H. Direct observation of crystal defects in an organic molecular crystals of copper hexachlorophthalocyanine by STEM-EELS. Sci. Rep. 2, 252 (2012).

    Article  Google Scholar 

  10. Crewe, A., Wall, J. & Langmore, J. Visibility of single atoms. Science 168, 1338–1340 (1970).

    Article  CAS  Google Scholar 

  11. Binh, V., Purcell, S., Garcia, N. & Doglioni, J. Field emission electron spectroscopy of single-atom tips. Phys. Rev. Lett. 69, 2527–2530 (1992).

    Article  CAS  Google Scholar 

  12. Diehl, R. et al. Narrow energy distributions of electrons emitted from clean graphene edges. Phys. Rev. B. 102, 035416 (2020).

    Article  CAS  Google Scholar 

  13. Chang, C., Kuo, H., Hwang, I. & Tsong, T. A fully coherent electron beam from a noble-metal covered W(111) single-atom emitter. Nanotechnology 20, 115401 (2009).

    Article  Google Scholar 

  14. Tafel, A., Meier, S., Ristein, J. & Hommelhoff, P. Femtosecond laser-induced electron emission from nanodiamond-coated tungsten needle tips. Phys. Rev. Lett. 123, 146802 (2019).

    Article  CAS  Google Scholar 

  15. Nakahara, H., Ichikawa, S., Ochiai, T., Kusano, Y. & Saito, Y. Carbon nanotube electron source for field emission scanning electron microscopy. e-J. Surf. Sci. Nanotechnol. 9, 400–403 (2011).

    Article  CAS  Google Scholar 

  16. Mamishin, S., Kubo, Y., Cours, R., Monthioux, M. & Houdellier, F. 200 keV cold field emission source using carbon cone nanotip: application to scanning transmission electron microscopy. Ultramicroscopy 182, 303–307 (2017).

    Article  CAS  Google Scholar 

  17. Zhang, H., Tang, J., Yuan, J. & Qin, L. C. Ultrabright and monochromatic nanowire electron sources. MRS Bull. 42, 511–517 (2017).

    Article  CAS  Google Scholar 

  18. Zhao, P. et al. A universal method to weld individual one-dimensional nanostructures with a tungsten needle based on synergy of the electron beam and electrical current. Nanomaterials 10, 469 (2020).

    Article  CAS  Google Scholar 

  19. Miyazaki, H. T., Miyazaki, H., Ohtaka, K. & Sato, T. Photonic band in two-dimensional lattices of micrometer-sized spheres mechanically arranged under a scanning electron microscope. J. Appl. Phys. 87, 7152–7158 (2000).

    Article  CAS  Google Scholar 

  20. Aoki, K. et al. Microassembly of semiconductor three-dimensional photonic crystals. Nat. Mater. 2, 117–121 (2003).

    Article  CAS  Google Scholar 

  21. Houdellier, F., Masseboeuf, A., Monthioux, M. & Hytch, M. New carbon cone nanotip for use in a highly coherent cold field emission electron microscope. Carbon 50, 2037–2044 (2012).

    Article  CAS  Google Scholar 

  22. Warren, B. X-Ray Diffraction (Dover Publications, 2012).

  23. Ishizuka, K. Contrast transfer of crystal images in TEM. Ultramicroscopy 5, 55–65 (1980).

    Article  CAS  Google Scholar 

  24. O’Keefe, M. ‘Resolution’ in high-resolution electron microscopy. Ultramicroscopy 47, 282–297 (1992).

    Article  Google Scholar 

  25. Kimoto, K. et al. Quantitative evaluation of temporal partial coherence using 3D Fourier transforms of through-focus TEM images. Ultramicroscopy 134, 86–93 (2013).

    Article  CAS  Google Scholar 

  26. Morishita, S., Mukai, M., Suenaga, K. & Sawada, H. Resolution enhancement in transmission electron microscopy with 60-kV monochromated electron source. Appl. Phys. Lett. 108, 013107 (2016).

    Article  Google Scholar 

  27. Kimoto, K., Kurashima, K., Nagai, T., Ohwada, M. & Ishizuka, K. Assessment of lower-voltage TEM performance using 3D Fourier transform of through-focus series. Ultramicroscopy 121, 31–37 (2012).

    Article  CAS  Google Scholar 

  28. Malis, T., Cheng, S. C. & Egerton, R. F. EELS log‐ratio technique for specimen‐thickness measurement in the TEM. J. Electron Microsc. Tech. 8, 193 (1988).

    Article  CAS  Google Scholar 

  29. Koch, C. T. Determination of Core Structure Periodicity and Point Defect Density along Dislocations. PhD thesis, Arizona State Univ. (2002).

  30. Sasaki, T. et al. Evaluation of probe size in STEM imaging at 30 and 60 kV. Micron 43, 551–556 (2012).

    Article  CAS  Google Scholar 

  31. Ishikawa, T., Okunishi, E., Kaneyama, T., Kondo, Y. & Matsumura, S. Aberration corrected electron microscopy enhanced for lower accelerating voltages. Microsc. Microanal. 21, 1599–1600 (2015).

    Article  Google Scholar 

  32. Yamashita, S. et al. Quantitative annular dark-field imaging of single-layer graphene-II: atomic-resolution image contrast. Microscopy 64, 409–418 (2015).

    Article  CAS  Google Scholar 

  33. Kimoto, K. et al. Element-selective imaging of atomic columns in a crystal using STEM and EELS. Nature 450, 702–704 (2007).

    Article  CAS  Google Scholar 

  34. Swanson, L. & Crouser, L. Total-energy distribution of field-emitted electrons and single-plane work functions for tungsten. Phys. Rev. 163, 622–641 (1967).

    Article  CAS  Google Scholar 

  35. Kasuya, K., Katagiri, S. & Ohshima, T. Stabilization of a tungsten <310> cold field emitter. J. Vac. Sci. Technol. B. 28, L55–L60 (2010).

    Article  CAS  Google Scholar 

  36. Kasuya, K. et al. Monochromatic electron emission from CeB6 (310) cold field emitter. Appl. Phys. Lett. 117, 213103 (2020).

    Article  CAS  Google Scholar 

  37. Kusunoki, T., Hashizume, T., Kasuya, K. & Arai, N. Stabilization of cold-field-emission current from a CeB6 single-crystal emitter by using a faceted (100) plane. J. Vac. Sci. Technol. B. 39, 013202 (2021).

    Article  CAS  Google Scholar 

  38. Krivanek, O. et al. Vibrational spectroscopy in the electron microscope. Nature 514, 209–212 (2014).

    Article  CAS  Google Scholar 

  39. Hage, F., Radtke, G., Kepaptsoglou, D., Lazzeri, M. & Ramasse, Q. Single-atom vibrational spectroscopy in the scanning transmission electron microscope. Science 367, 1124–1127 (2020).

    Article  CAS  Google Scholar 

Download references


This study was supported by the National Institute for Materials Science Advanced Measurement and Characterization Project.

Author information

Authors and Affiliations



H.Z. carried out the experiments and wrote the paper. Y.J. and A.N. carried out physical evaluation of the LaB6 NW emitter with TEM. A.I. developed high voltage electronics for the LaB6 NW emitter electron gun. A.Y. acquired STEM and TEM data. C.O. and K.K. contributed to the (S)TEM image analysis and simulation. T.K., H.T.M. and H.W. carried out nanomanipulation. N.T. contributed to the NW synthesis. Y.Y., D.F., S.-i.K. and H.M. coordinated the project.

Corresponding author

Correspondence to Han Zhang.

Ethics declarations

Competing interests

The authors Y.J., A.N., A.I., A.Y., S.-i.K. and H.M. are affiliated with JEOL Ltd (Akishima, Tokyo, Japan), which is a producer of electron microscopes, including TEMs.

Additional information

Peer review information Nature Nanotechnology thanks Gregory Schwind and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Extended Data Fig. 1 Collimator effect.

(a) LaB6 nanowire emitter SEM image showing a bare support needle tip without collimator structure; Field emission pattern shows an axial deviation angle of 6o; Field emission electron trajectory calculated for the emitter structure using finite element method; (b) LaB6 nanowire emitter SEM image showing a support needle tip with a collimator structure; Field emission pattern shows an axial deviation angle less than 1o; Field emission electron trajectory calculated for the emitter structure using finite element method; (c) Finite element simulation of the axial deviation angle, ϕ, dependence on nanowire suspension length, l, for the bare needle tip structure (red) and the collimator tip structure (blue). Spade shaped data were experimentally measured.

Extended Data Fig. 2 HRTEM images.

(a) Structure of the LaB6 nanowire TEM. Components labelled along beam path from top to bottom: nanowire emitter, condenser lens aperture, specimen, annular dark field detector, Faraday cage, image screen, and EELS spectrometer; (b) The 800kx HRTEM image taken by using the LaB6 NW emitter. Red rectangle marked the region where the FFT diffractogram of Fig. 2d is created from; (c) That taken by using the original W (310) electron gun with same imaging condition as (b); Red square marked the region used to generate diffractogram through FFT.

Extended Data Fig. 3 Titan3 images.

(a) Energy spread of electron beam produced by a Schottky electron gun with the monochromator in off state; (b) Energy spread of electron beam produced by a monochromated Schottky electron gun. (c) A high-resolution TEM image taken on Si (110) specimen using the beam condition of (a). Inset showing FFT diffractogram; (d) That using beam condition of (b). Inset showing FFT diffractogram.

Extended Data Fig. 4 Titan3 CTF.

(a) Chromatic envelop functions plotted for TEMs using LaB6 nanowire emitter, monochromated Schottky emitter, and unmonochromated Schottky emitter, respectively. Dashed curve representing contrast transfer function for the LaB6 nanowire TEM until the first zero-crossing. (b) Blue and red outlined diffractograms of the TEM images recorded using the Schottky emitter under unmonochromated and monochromated conditions respectively. Three additional reflection spots appearing in the monochromated TEM images, being labelled with their corresponding lattice indices and spacings.

Extended Data Fig. 5 Diffractogram comparison.

(a) Diffractograms from the W (310) TEM (outlined in red) and the LaB6 NW TEM (outlined in black). (115) spot intensity relative to central transmission spot intensity was compared between two electron guns using a line profile. (b) Same comparison about the (224) spot. Comparison about (115) spot showed that the relative intensity ratio between LaB6 NW TEM and W (310) TEM was 2:1 and that about (224) spot is 4:3.

Extended Data Fig. 6 Probe profiles.

(a) 2D electron probe profile simulated using QSTEM based on diffraction and lens aberration conditions of the experiment. Image width: 200pm; (b) A gaussian-shaped beam profile simulating additional probe broadening effect defined as source image size. Image width: 200pm; (c) Theoretical probe profile simulated by convoluting (a) with (b). Image width: 200pm; (d) Line profiles of (a), (b), (c), showing the 87.6pm FWHM of the convoluted probe.

Extended Data Fig. 7 STEM images.

(a) HAADF image taken on a Si (110) specimen using W (310) electron gun. Inset showing the highest resolved spatial frequency of 96pm; (b) Line profile collected from the rectangle-marked region in (a) plotted together with line profiles from LaB6 nanowire STEM image; (c) Raw image data of Fig. 3d.

Extended Data Fig. 8 Stability.

(a) Probe current measured at the objective lens entrance of a SEM equipped with a LaB6 nanowire cold field emission gun with a vacuum level of ~10−8Pa; (b-d) Magnified view of probe current 1 minute profile at 10th, 240th and 480th minute, showing consistent low peak-to-peak noise ratios below 0.5%. Vacuum condition in the TEM electron gun for the LaB6 NW emitter test is in the same level or better than the electron gun shown here. Similar or better performance is assumed for the TEM setup.

Extended Data Fig. 9 Energy spread.

(a) Unmonochromated EELS ZLP comparison among LaB6 nanowire emitter, W (310) emitter and Schottky emitter, used in aberration corrected TEMs. 0.2eV and 0.27 eV are the lowest possible FWHM energy spreads measured for LaB6 nanowire emitter and W (310) emitter in the same JEM-Arm200F TEM; (b) Energy spread versus reduced angular current density plots for the LaB6 nanowire emitter and W (310) emitter; (c) Reduced angular current density plotted against extraction voltage for LaB6 nanowire emitter and W (310) emitter.

Extended Data Fig. 10 Emission area.

(a) Field ion microscopy pattern of (100) apical facet of a LaB6 NW emitter; (b) Field emission microscopy pattern of the same nanowire using the same emitter-screen setup as (a). Red rectangle marking the emission area for (100) facet; (c) Field ion microscopy pattern of the (111) facet of a W needle emitter; (d) Field emission microscopy pattern of the same W needle using the same emitter-screen setup as (c). Red rectangle marking the emission area for (310) facet.

Supplementary information

Supplementary Information

Supplementary discussion.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Zhang, H., Jimbo, Y., Niwata, A. et al. High-endurance micro-engineered LaB6 nanowire electron source for high-resolution electron microscopy. Nat. Nanotechnol. 17, 21–26 (2022).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:


Quick links

Find nanotechnology articles, nanomaterial data and patents all in one place. Visit Nano by Nature Research