Detection of Vacancies
- Practical Electron Microscopy and Database -
- An Online Book -  




Investigating individual point defects, e.g. monovacancies, using TEM-related techniques was believed to be difficult because this requires both atomic sensitivity and atomic resolution and the specimens need to be very thin such that one can detect the individual point defects from the image contrast.

Since a monovacancy was first observed by TEM in low-dimensional carbon structures [1], the studies of point defects in monolayered materials using TEM have been attracting scientists' interest. For instance, the vacancies and topological defects in grapheme, edge structures and point defects in single layer hexagonal boron nitride (h-BN) [2, 7], monovacancies in WS2 nanoribbons [3] have been successfully identified at atomic level [4–6]. Unfortunately, this type of analyses was only achieved in “natively” grown nanomaterials but no applications have been performed successfully in samples prepared from bulk materials, e.g. by FIB (focused ion beam), mainly because of preparation-induced damages.

Figure 2227 shows a boron monovacancy [8, 9] (indicated by the darkest contrast in (a)), in single-layered h-BN (hexagonal boron-nitride), induced by the knock-on effect.

A boron monovacancy in defective single-layered hexagonal boron-nitride

Figure 2227. (a) A boron monovacancy shown by the darkest contrast in the HAADF-STEM image of single-layered h-BN and (b) A corresponding atomic model (red: nitrogen, blue: boron). Adapted from [7]

Table 2227. Other Detections of Vacancies.

Technique Details
Electron diffraction and simulation Orientation relationship of (10-10)YbSi2-x/(11-2)Si
Diffraction pattern of a planview TEM sample of ErSi2-x on Si(001) annealed at 700 °C. The extra spots are due to ordered vacancy structure are marked by "O". [10]
Orientation relationship of (10-10)YbSi2-x/(11-2)Si
Schematic plots showing: (a) the ordered vacancy structure, (b) a simulated electron diffraction pattern viewed along the [1-100] silicide direction and (c) three-dimensional vacancy ordering structure. The vacancy positions are indicated as empty squares. [10]







[1] Ayako Hashimoto, Kazu Suenaga, Alexandre Gloter, Koki Urita, & Sumio Iijima, Nature (London) 430, 870 (2004).
[2] O. Krivanek et al., Nature (London) 464, 571 (2010).
[3] Z. Liu et al., Nature Commun., 2, 213 (2011).
[4] K. Suenaga et al., Nature Nanotech. 2, 358 (2007).
[5] J. Meyer et al., Nano Lett. 8, 3582 (2008).
[6] C. O. Girit et al., Science 323, 1705 (2009).
[7] Kazu Suenaga, Haruka Kobayashi, and Masanori Koshino, Core-Level Spectroscopy of Point Defects in Single Layer h-BN, Physical Review Letters, 108, 075501 (2012).
[8] C. Jin et al., Phys. Rev. Lett. 102, 195505 (2009).
[9] J. Meyer et al., Nano Lett. 9, 2683 (2009).
[10] W.C. Tsai, H.C. Hsu, H.F. Hsu, L.J. Chen, vacancy ordering in self-assembled erbium silicide nanowires on atomically clean Si(001), Applied Surface Science 244 (2005) 115–119.